Calorimetry

Both heat capacity (C) and specific heat capacity (c) deal with the amount of heat required to change a compound’s temperature by 1 Kelvin. Specific heat capacity (c) deals with changing 1 gram of a compound.

Constant Volume Calorimetry

By using calorimetry we can measure the thermal energy of a reaction (system) by measuring the change in heat of the surroundings.

Concept: Heat capacity vs. Specific Heat Capacity

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Video Transcript

Welcome back guys! In this new video, we're going to take a look at calorimetry under a constant volume.
Now first we're going to say that every object has its own heat capacity. And just remember heat capacity uses a capital C, and this is just the amount of heat that's required to change an object's temperature by 1 Kelvin (K). Here we're just going to say heat capacity is simply heat/the change in temperature, so Final - Initial. And we're going to say the units are usually in Joules (J)/Kelvin or kiloJoules/Kelvin.
q J
C = ∆T [ in units of K ]

Sometimes your professor may even do it over Degrees Celsius, so just look to see what units were they want the answer to be in. That's what you always have to make sure so that you get the correct answer.
Now similar to heat capacity, there's another property. This property is known as Specific Heat Capacity, and notice that this one is lower case c, and this is the amount of heat that's required to change 1g of substance by 1K.
So here we're just going to introduce the concept of mass, and mass here would be in grams. So it's similar to heat capacity but more in depth, where talks about mass. Now what we're going to say here is if we know the specific heat capacity of a substance, we can rearrange this formula here so that we can solve for the amount of heat absorbed or released. So if we want to rearrange this equation up here, so C = q/m * change in temperature.
q
C = m * ∆T

Just multiply both sides by mass * change in temperature.
q
m * ∆T (C) = m * ∆T m * ∆T

And then you say that q = mcAT.
q = mc∆T
So just remember q = mcAT, just read the delta sign, the triangle as an A. So that's the easy way for you to remember the equation, q = mcAT. This is the equation that we use anytime they give us specific heat capacity, and we know that change in temperature, and they give us the mass of an object.
Now based on the concept we've just looked at let's take a look at this Question here. It says:
At constant volume, the heat of combustion of a particular compound is -4621.0 kJ/mol. We say when 2.319 grams of this compound (molar mass = 192.75 g/mol), remember it has a molar mass that I give to you, was burned in a bomb calorimeter, the temperature of the calorimeter (including its contents) rose by 3.138 oC. What is the heat capacity of the calorimeter in J/K?
First of all, this image that we have here is called a bomb calorimeter. It's a way of us actually figuring out how much energy does an object contain in it. The way it works is, we have our sample put inside to the small little bowl here, and that is placed inside of those water. This whole unit is referred to as a bomb. And what's going to happen is, we're going to actually use these rods here, and we're going to send an electrical current, and it's actually going to cause this sample to explode inside of the bomb calorimeter. So that's why it's called the bomb calorimeter because we actually cause the contents to explode. And when they explode, they're going to give off some heat. Now there's a temperature in the water, this temperature is actually going to record how much the water temperature increases by. In that way, we can figure out how much heat that that sample release and from that we can figure out how many calories it has, how much heat it started with, we could find out a lot of information. This is the way to do certain food sciences, to figure out the calories we have in a food. They use similar technique such as this.
Now we talked about Joules as being the standard type of energy for heat, but remember you could also have instead of Joules for q you could have kiloJoules, but you could also have calories, large calories, these are the calories that you see in food, and kilowatt-hours. So these are other units, energy conversion factors that we can use in place of Joules for q. Now we're not going to work on converting from Joules to calories or kilowatt-hours, I just want to give you guys these tables so that you can see all the different types of energy conversions that you should know for lecture.
Now let's take a look at this question, we want to calculate heat capacity. Remember this is capital C, and so heat capacity = q/change in temperature. And what we need to realize here is, we need to isolate Joules, we need to find Joules for q, and we need the temperature to be in Kelvin. We already have half of it right off the bat, the easy part. The easy part here is I told you that the temperature rose by this much. 

Concept: Bomb Calorimeter

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Video Transcript

That right there represents our change in temperature, but the thing is we just need to change those oC into K. And how do we do that? Remember the goal from oC to K, you just add 273.15 to it, when we do that we get 276.288 K.
3.138 oC + 273.15 = 276.288 K
Now what we have to do is we have to isolate q, we have to find Joules. Now the closest place we're going to find Joules are right here in kiloJoules. So we need to find a way of isolating those kiloJoules there. Now the only way I can isolate those kiloJoules is if I find a way to cancel out these moles that we have. And the way I'm going to cancel out those moles is if I convert these grams that I gave to you into moles and multiply times this whole thing. So what we're going to do is we're going to start out with 2.319 g, now we can change this into moles because I gave you the molecular weight, the molar mass of the object. So we're going to say for every 1 mole of this substance it's 192.75 g, grams cancel out and we've just isolated our moles.
1 mol
2.319 g x 192.75 g

I'm going to take myself out of the image so that we'll have more room to work with guys. So we have moles now, now I can just multiply times the heat of combustion, so this would be -4621.0 kJ on top, 1 mol on the bottom. Moles cancel out and now I have kiloJoules isolated.
1 mol -4621.0 kJ
2.319 g x 192.75 g x 1 mol

But remember I don't want kiloJoules, I want Joules. So one more step, kiloJoules go on the bottom, Joules on the top. Kilo is a metric prefix, so for every 1 kilo it's 103. When we work all of that out that gives me -55 600 J, so that's my q. So I'm going to plug it up here. So divide that by the temperature we just isolated and you'll get -201 J/K.
1 mol -4621.0 kJ 10J
2.319 g x 192.75 g x 1 mol x 1 kJ

= - 55 600 J

So I'm going to plug it up here. So divide that by the temperature we just isolated and you'll get -201 J/K.
q
C = ∆T
= - 55 600 J
276.288 kJ
= - 201 J/K

Now this question seems like a lot of information into this, but the thing is just focus on what they're asking us to find, they wanted us to find heat capacity. Heat capacity is just simply q/change in temperature, we knew change in temperature immediately so we just convert it that to Kelvin and then you're now to work on isolating the one variable you needed, you needed kJ, you need to isolate kJ. We isolated that by changing the grams I gave you into moles and then multiplying times the heat of combustion. Now when they say heat of combustion, remember heat means q, but more importantly here it means delta H. They could have said that enthalpy of combustion, also that be the same exact thing. Okay so just remember heat and enthalpy is the same thing.

A bomb calorimeter measures the amount of calories within a substance through combustion. In other words, we “blow it up” and measure the amount of heat it releases. 

Constant Volume-Calorimetry Calculations

If you are given energy or heat, with specific heat capacity and mass then you will most likely use q = mcΔT.

Example: In an experiment a 9.87 carat (1 carat = 0.200g) diamond is heated to 72.25oC and immersed in 22.08 g of water in a calorimeter. If the initial temperature of the water was 31.0oC what is the final temperature of the water? (cdiamond = 0.519) (cwater = 4.184 ). 

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Problem: A sample of copper absorbs 35.3 kJ of heat, which increases the temperature by 25 degrees Celsius, determine the mass (in kg) of the copper sample if the specific heat capacity of copper is 0.385 J/g *C.

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When dealing with heat it is important to remember that if one compound is gaining heat that means another compound is losing heat.

Problem: 50.00 g of heated metal ore is placed into an insulated beaker containing 822.5 g of water. Once the metal heats up the final temperature of the water is 32.08 degrees Celsius. If the metal gains 14.55 kJ of energy, what is the initial temperature of the water?

5m

Constant Pressure Calorimetry

The enthalpy or heat of a reaction can be calculated through the use of a coffee cup calorimeter. 

Concept: Coffee Cup Calorimeter

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Video Transcript

Welcome back, guys! In this new video, we're going to take a look at chemical reactions when the calorimetry is done under constant pressure. What you’re going to see here is this image right here. We're going to say that this is called a coffee calorimeter. We're going to say it’s used basically to help us find the enthalpy of a reaction. Remember, enthalpy just means delta H. The coffee cup calorimeter has certain parts to it. Here we have the stirrer, which just helps us to mix the water that surrounds our sample. Here we’re going to have our thermometer, which measures the temperature change involved when the sample undergoes its chemical reaction. The sample was going to be releasing heat. The water is going to be absorbing that heat. The thermometer is just to calculate the change in temperature that the water undergoes. Here we’re going to have the two styrofoam cups that are placed together. They work as insulation. That way, no heat is lost to the outside environment. All the temperature or energy changes that occur are going to happen between the water and the sample. Here we're going to have our water. Our water acts as the surroundings. Here we're going to have our sample, which is going to undergo the chemical reaction. This represents our system.
Remember, under constant pressure it's possible for us to calculate the enthalpy of the reaction through the use of this coffee cup calorimeter.

Concept: Calculating the Heat of the Solution

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Video Transcript

Now let's take a look at it this example question. Here it says you place 50 ml of 0.100 molar NaOH into a coffee cup calorimeter at 50 degrees Celsius and carefully add 75 mls of 0.100 molar hydrochloric acid also at 50 degrees Celsius. After stirring, the final temperature of the solution is 76.12 degrees Celsius. Heat capacity and the density of water are also given.
From this, we have to calculate two parts. For part A, we have to figure out what is the heat or Q of the solution in joules. Since we're going to need room to do both of these questions, I'm going to take myself out of the image guys, so we have more room to work with.
What we should realize is that we need to find the heat of the solution. The problem is it's hard to do it directly. But we can find the Q of the water. If we know Q of water, we can then say Q of water equals negative Q of the solution. Remember, in this process, the sample will undergo a chemical reaction and release heat that's why it’s negative. The water will absorb that heat that's why it's positive. We can find the Q of water because we can say Q of water equals mCΔT. We already know the specific heat water. I gave it to you. I said it’s 4.184 joules over degrees times Celsius. Our temperature change, our final temperature is 76.12 degrees Celsius. Our initial for both samples when we mix them together were 50 degrees Celsius.
The harder part is just figuring out what the mass of the water is. But we can figure this out because when we say 50 ml and 75 ml, those two things actually represent the volume of water. What's really going on here that we have that many milliliters of water and dissolved within it are those moles of NaOH and HCl. We're going to take those 50 mls and that 75 ml and add them together to give me 125 mls of water. Since I know the density of water here, I can use that to find the grams of water. Multiply this times the density. Mls cancel out and I have 125 grams of water, which I can just plug into here.
When I multiply everything out, that gives me 13,660.8 joules as the Q of water. We can just plug it into here so we’re going to have 13,660.8 joules equals negative Q of solution. But I want Q of solution, not negative Q of solution. So then all you have to do is divide both sides by -1. Now, Q of solution equals negative 13,660.8 joules as your final answer. Here we’re not concerning ourselves with number of significant figures because here we’re just trying to figure out what the answer is. If you will get this type of question on your exam, your professor would specify do they want sig figs or not.

The heat of the solution can be determined by first determining the heat of water

Concept: Calculating the enthalpy of the reaction

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Video Transcript

For B, we have to calculate the enthalpy, delta H, in joules per mole for the formation of water. Here we have to figure out the enthalpy of water. We're going to say delta H of reaction equals Q of solution divided by the moles of whatever they're asking us to find. Here, they’re asking for the formation water so it’s moles of water. We already have half of this because we just figured out what the Q of solution was, so we’ll just plug it in. Now what we have to do is we have to figure out how many moles of water we have.
What we should realize here is I give you information on NaOH and HCl. Remember, the word of when it’s in between two numbers means multiply. Remember, when I say big M that means molarity. Molarity equals moles over liters. When I say 0.100 molar NaOH, that really means 0.100 moles of NaOH over 1 liter. We always assume it's always moles over liters.
If you guys don’t remember this too well, go back to a few videos past where we talked about molarity and molarity in stoichiometry because to do this question, it's essential that you remember those steps from earlier. We’re going to work it out down here. Since I gave you information on two reactants and I'm asking you how much product do you have in moles, this is really a limiting reactant type of question. We're going to have to first do it with the molarity of NaOH, see how many moles of water that gives us then do the same thing with HCl. Since this is a limiting reactant type of question, the one that gives us a smaller amount of moles of water, those are those moles we’re going to use. We have 50 ml of 0.100 molar NaOH. I need to change my ml into liters. 1 ml on the bottom, 10 to the negative 3 liters on the top. Mls cancel out and I finally isolate liters. Now that I have liters, I can multiply it times the molarity to find the moles of NaOH. We need the moles of water though. We need to go from these moles I've given that we just found to our moles of unknown. Remember when we do that jump, we do a mole to mole comparison. We look at the coefficients in the balanced equation. According to our balanced equation, for every one mole of NaOH, we have one mole of water. NaOH on the bottom and mole of H2O what we’re looking for in the top. Since this is in 10 to the negative 3, put it in brackets. When we work it out, we get 0.005 moles of water.
Now we have to do the same thing with HCl. We have 75 ml of 0.100 molar HCl. Same thing, we change the mls into liters first then we multiply it times the molarity. For every one mole of HCl, we have one mole of H2O. Liters cancel out, moles cancel out. We have 0.0075 moles of water. Remember, since this is the limiting reactant type of question, we're going to go with the smaller moles of water. Those are the moles we're going to plug down here to find our enthalpy. When we plug that in, we get back negative 2.73 times 10 to the 6 joules per mole.
This question had a lot of parts to it. It became even harder because we had to incorporate concepts that we learned a few videos back. Just because we passed molarity and stoichiometry involved with them doesn't mean we don't have to see it again this semester. Those types of ideas always resurface at some point. We had to use them in order to solve this question. Remember, if we’re at constant pressure, that's when we use a coffee cup calorimeter. Its whole purpose is to help us find the enthalpy of a reaction. Remember, if your enthalpy, I may not have said that but if your enthalpy is positive, that means you’re absorbing energy or absorbing heat so you're endothermic. If you're releasing heat or releasing energy by the system, then it's exo. It’s negative delta H. Just remember the concepts that we covered here and the approaches we take. When you see a question like this, you'd be better prepared to do it.

Calorimetry Additional Practice Problems

Heat is applied to change the temperature of a water sample from 11.5°C to 25.0°C. If the sample welighs 86.45g, how much heat is needed? 

(a) 4.55 kJ 

(b) 4.88 kJ 

(c) 4.25 kJ

(d) 4.74 kJ 

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Calculate the enthalpy of methanol (CH3OH(l) (MW = 32.0 g/mol), if a 2.885 g sample of methanol is burned in a bomb calorimeter (Kc = 727.1 J/°C) containing 1.200 kg of water (Cp = 4.184 J/°C). The temperature of the calorimeter increases by 11.38°C. 

a. 635 kJ/mol

b. -1.02 x 106 kJ/mol 

c. -726 kJ/mol  

d. -91.9 kJ/mol  

e. -65.4 kJ/mol 

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In the laboratory a "coffee cup " calorimeter, or constant pressure calorimeter, is frequently used to determine the specific heat of a solid, or to measure the energy of a solution phase reaction. 

A student heats 69.07 grams of iron to 97.56°C and then drops it into a cup containing 81.71 grams of water at 22.09°C. She measures the final temperature to be 28.09°C. 

The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.82 J/°C. 

Assuming that no heat is lost to the surroundings calculate the specific heat of iron. 

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Suppose you had a bomb calorimeter containing 500 mL of water at 25°C that you wanted to heat to exactly 95°C. You are using as a fuel the saturated fatty acid hexanedecanioc acid (C16H32O2), more commonly known as palmitic acid found in palm oil and animal fats. 

Use the following information to calculate how many grams of palmitic acid you should place into the bomb.
Cbomb = 900 J/°C 

Cwater = 4.184 J/g°C 

density of water = 1.0 g/mL 

ΔHC-16.0 = 10, 071 kJ/mol (Heat of combustion of palmitic acid, assume ΔH = ΔE)

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A 35 gram sample of copper (Csp(Cu) = 0 685 J/(g°C) is placed in a constant-pressure calorimeter containing 100 g of water that just stopped boiling. After some time the temperature of the water becomes constant at 92.3°C. What was the initial temperature of the copper block? Assume no heat is lost to the surroundings.

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Calculate the amount of heat required to heat a 50 kg sample of ethanol from 13.0°C to 17.0°C. Specific heat capacity of ethanol is 2.42 J/g°C.

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Calculate the amount of heat required to raise the temperature of a 38 g sample of water from 9°C to 22°C. 

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A 27.72 g sample of a substance is initially at 21.1°C. After absorbing 2781 J of heat, the temperature of the substance is 161.3°C. What is the specific heat (SH) of the substance? 

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A hot tub is filled with 450 gal of water. (Figure 1) 

Part B 

What is the mass, in kilograms, of water in the tub? 

Express your answer to two significant figures and include the appropriate units. 

Part C 

How many kilocalories are needed to heat the water from 34°F to 177°F? 

Express your answer to two significant figures. 

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Part A

If you used the 8400 kilojoules you expend in energy in one day to heat 60000 g of water at 10°C, what would be the rise in temperature? 

Express your answer using one significant figure. 

Part B

What would be the new temperature of the water? 

Express your answer using one significant figure. 

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A 49.3-g piece of metal is heated to 288 °C and dropped into 100.0 g of water at 12.0 °C. The metal and water come to the same temperature of 24.0 °C. What is the specific heat, in J/g °C, of the metal?

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The specific heat of a certain type of metal is 0.128 J/(g •°C). What is the final temperature if 305 J of heat is added to 63.7 g of this metal initially at 20.0°C.

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The specific heat of a certain type of cooking oil is 1.75 J/(g • °C). How much heat energy is needed to raise the temperature of 2.91 kg of this oil from 23°C to 191°C?

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A 34.22 g sample of a substance is initially at 282°C. After absorbing 2887 J of heat, the temperature of is 181.8°C. What is the specific heat (c) of the substance? 

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What is the specific heat of copper if it takes 93.8 cal to raise the temperature of a 85 g copper bar by 12.0. 

Express your answer using two significant figures.

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Titanium reacts with iodine to form titanium(III) iodide, emitting heat. 

2Ti (s) + 3I2 (g) → 2TiI3 (s)           ΔH°rxn = 839 kJ 

Part A

Determine the masses of titanium and iodine that react if 1.69 x 103 kJ of heat is emitted by the reaction. 

Express your answer using three significant figures. 

Part B

Express your answer using three significant figures.

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During an experiment, a student adds 1.23 g of CaO to 200.0 mL of 0.500 M HCI. The student observes a temperature increase of 5.10°C. 

Assuming the solution's final volume is 200.0 mL, the density if 1.00 g/mL, and the heat capacity is 4.184 J/(g.°C), calculate the heat of the reaction, ΔHrxn.

CaO (s) + 2H+ (aq) → Ca2+ (aq) + H2O (l) 


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Suppose that 1.14 g of rubbing alcohol (C6H8O) evaporates from a 70.0 g aluminum block. 

Part A

If the aluminum block is initially at 25°C, what is the final temperature of the block after the evaporation of the alcohol? Assume that the heat required for the vaporization of the alcohol comes only from the aluminum block and that the alcohol vaporizes at 25°C. Heat of vaporization of the alcohol at 25°C in 45.4 kJ/,mol. 

Express your answer using two significant figures.

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Four ice cubes at exactly 0°C with a total mass of 55.0 g are combined with 120 g of water at 85°C in an insulated container. (ΔHfun° = 6.02 kJ/mol, cwater = 4.18 J/g • °C) 

Part A

If no heat is lost to the surroundings, what is the final temperature of the mixture? 

Express your answer using two significant figures.

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A 26.6 g sample of Au metal (c = 0.13 J/g°C) is heated to 88.0°C and then placed into a beaker containing 173 g of 13.4 °C water (c = 4.184 J/g°C). The metal and water are then left until they come to equilibrium. What is ΔT for Au given to three significant figures?

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Consider the following reaction: 

NaCl (s) → Na+ (aq) + Cl- (aq)         ΔH = 3.88 kJ/mol 

In a coffee-cup calorimeter you dissolve 21.9 g of this salt in 108 g of water at 27.7°C. 

What will be the final temperature of the solution formed? 

Assume the specific heat of the solution is 4.184 J/g°C, and that there is no heat loss to the surroundings. Please enter your answer to the correct number of significant figures.

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Exactly 10.1 mL of water at 31.0°C are added to a hot iron skillet. All of the water is converted into steam at 100.0°C. The mass of the pan is 1.50 kg and the molar heat capacity of iron is 25.19 J/(mol • °C). What is the temperature change of the skillet?

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If 1495 J of heat is needed to raise the temperature of a 318 g sample of a metal from 55.0°C to 66.0°C, what is the specific heat capacity of the metal?

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A 59.69 g sample of a substance is initially at 241°C. After absorbing 1197 J of heat, the temperature of is 169.5°C. What is the specific heat (c) of the substance?

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The specific heat of a certain type of cooking of is 1.75 J/(g • °C). How much heat energy is needed to raise the temperature of 2.56 kg of this oil from 23°C to 191°C?

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Liquid sodium is being considered as an engine coolant. How many grams of liquid sodium (minimum) are needed to absorb 4.30 MJ of energy (in the form of heat) if the temperature of the sodium is not to increase by more than 10.0°C? Use Cp = 30.8 J/(K • mol) for Na(l) at 500 K.

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An 80 0-gram sample of a gas was heated from 25°C to 225°C. During this process. 346 J of work was done by vie system and its internal energy increased by 9225 J. What is the specific heat of the gas?

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When 2112 J of heat energy is added to 45.8 g of ethanol. C2H6O, the temperature increase by 18.8°C. Calculate the molar heat capacity of C2H6O.

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If you combine 350.0 mL of water at 25.00°C and 110.0 mL of water at 95.00°C, what is the final temperature of the mixture? Use 1.00 g/mL as the density of water.

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The heat of vaporization of water is 40.66 kJ/mol. How much heat is absorbed when 2.04 g of water boils at atmospheric pressure? 

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A 15.99 g sample of metal heated in a test tube submerged in 100.00°C water. It was then placed directly into a coffee cup calorimeter holding 51.95 g of water at 22.10°C. The temperature of the water increased to 24.99°C, determine the specific heat capacity of the metal. 

If the calorimete had absorbed 197.3 J and we factored that quantity into our calculation, what would the specific heat of the metal been?

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Be sure to answer all parts.

A 0.1775-g sample of solid magnesium is burned in a constant-volume bomb calorimeter that has a heat capacity of 3024 J/°C. The temperature Increases by 1.452°C. 

(a) Calculate the heat given off by the burning Mg in kJ/g. 

(b) Calculate the heat given off by the burning Mg in kJ/mol. 

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Enter your answer in the provided box.

A 25.95-g sample of methanol at 35.6 °C is added to a 38.65-g sample of ethanol at 24.7 °C in a constant-pressure calorimeter. If the final temperature of the combined liquids is 28.5 °C and the heat capacity of the calorimeter is 19.3 J/°C, determine the specific heat of methanol. J/g • C

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Consider the following reaction. 

2Fe2O3 → 4Fe + 3O2     ΔH°rxn = + 824.2 kJ 

The decomposition of 33.0 g of Fe2O3 results in 

(a) the release of 85.2 kJ of heat. 

(b) the release of 1.70 x 102 kJ of heat. 

(c) the absorption of 85.2 kJ of heat. 

(d) the absorption of 1.70 x 102 kJ of heat. 

(e) the absorption of 13600 kJ of heat. 

(f) the release of 13600 kJ of heat.

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The specific heat of a certain type of cooking oil is 1.75 J/(g • °C). How much heat energy is needed to raise the temperature of 2.02 kg of this oil from 23 °C to 191 °C?

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A 38.40 g sample of a substance is initially at 21.6 °C. After absorbing 2597 J of heat, the temperature of the substance is 126.6 °C. What is the specific heat (c) of the substance?

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The specific heat of a certain type of metal is 0.128 J/(g • °C). What is the final temperature if 305 J of heat is added to 57.9 g of this metal initially at 20.0  °C?

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If you combine 370.0 mL of water at 25.00 ° C and 110.0 mL of water at 95.00 °C. what is the final temperature of the mixture? Use 1.00 g/mL as the density of water.

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If the heat of combustion for a specific compound is -1040.0 kJ/mol and its molar mass is 73.87 g/mol, how many grams of this compound must you burn to release 176.60 kJ of heat?

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Enter your answer in the provided box.

Calculate the heat (in kJ) associated with the cooling of 348 g of mercury from 55.6 °C to 12.0 °C.

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Enter your answer in the provided box.

A 479 g sample of water has an initial temperature of 19.0 °C. After 76.2 kJ of energy is added to the water sample, what will be its final temperature?

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A 2.97 g lead weight, initially at 10.7 °C is submerged in 7.72 g of water at 52.9 °C in an insulated container.

You may want to reference [(3) pages 256 - 262] section 6.4 while completing this product.

What is the final temperature of both the weight and the water at thermal equilibrium? 

Express the temperature in Celsius to three significant figures.

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Enter your answer in the provided box.

A sheet of gold weighing 8.2 g and at a temperature of 17.6 °C is placed flat on a sheet of iron weighing 18.1 g and at a temperature of 52.6 °C. What is the final temperature of the combined metals? Assume that no heat is lost to the surroundings. 

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The propane fuel (C3H8) used in gas barbeques buns according to the following thermochemical equation: 

C3H(g) + 5O2 (g) → 3CO2 (g) + 4H2O (g)    ΔH°rxn = -2217kJ 

If a pork roast must absorb 1600 kJ to fully cook, and if only 12% of the heat produced by the barbeque is actually absorbed by the roast, what mass of CO2 is emitted into the atmosphere during the grilling of the pork roast? Express your answer using two significant figures.

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Zinc metal reacts with hydrochloric acid according to the following balanced equation. 

Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g) 

When 0.116 g of Zn(s) is combined with enough HCl to make 52.3 mL of solution in a coffee-cup calorimeter, all of the zinc reacts, raising the temperature of the solution from 21.5 °C to 24.7 °C. 

Part A

Find ΔHrxn for this reaction as written. (Use 1.0 g/mL for the density of the solution and 4.18 J/g • °C as the specific heat capacity.)


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Dry ice is solid carbon dioxide. Instead of melting, solid carbon dioxide sublimes according to the following equation: CO2 (s) → CO2 (g). When dry ice is added to warm water, heat from the water causes the dry ice to sublime more quickly. The evaporating carbon dioxide produces a dense fog often used to create special effects. In a simple dry ice fog machine, dry ice is added to warm water in a Styrofoam cooler. The dry ice produces fog until it evaporates away, or until the water gets too cold to sublime the dry ice quickly enough. Suppose that a small Styrofoam cooler holds 15.0 liters of water heated to 83 °C. 

Part A

Use standard enthalpies of formation to calculate the change in enthalpy for dry ice sublimation. (The ΔH°f for CO2 (s) is -427.4 kJ/mol). Express your answer using three significant figures. 

Part B

Calculate the mass of dry ice that should be added to the water so that the dry ice completely sublimes away when the water reaches 18 °C. Assume no heat loss to the surroundings. Express your answer using two significant figures.

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An ice cube of mass 8.5 g is added to a cup of coffee, whose temperature is 85 °C and which contains 130 g of liquid. Assume the specific heat capacity of the coffee is the same as that of water. The heat of fusion of ice (the heat associated with ice melting) is 6.0 kJ/mol. 

Part A

Find the temperature of the coffee after the ice melts. Express your answer using two significant figures.

Watch Solution

A 285 g piece of granite, heated to 6.10 x 102 °C in a campfire, is dropped into 1.30 L water (d = 1.00 g/mL) at 25.0 °C. The molar heat capacity of water is cp, water = 75.3 J/(mol • °C), and the specific heat of granite is Cs, granite = 0.79 J/(g • °C). Calculate the final temperature of the granite.

Watch Solution

The specific heat of solid copper is 0.385 J/(g • °C). What thermal energy change occurs when the temperature of a 53.60 g sample of copper is cooled from 44.3 °C to 10.2 °C? Be sure to give your answer the proper sign. 

This amount of heat is used to melt solid ice at 0.0 °C. The molar heat of fusion of ice is 6.00 kJ/mol. How many moles of ice are melted?

Watch Solution

If 285 grams of water at 21 °C absorbs 287 kJ of heat from a mountain climber's stove at an elevation where the boiling point of water is 87 °C, is this amount of energy sufficient to heat the water to its boiling point? 

          (a) Yes 

          (b) No 

How many kJ are required to heat the water to its boiling point?

Watch Solution

Exactly 10.3 mL of water at 31.0 °C are added to a hot iron skillet. All of the water is converted into steam at 100 °C. The mass of the pan is 1.15 kg and the molar heat capacity of iron is 25.19 J/(mol • °C). What is the temperature change of the skillet?

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A 29.75 g piece of iron and a 23.40 g piece of gold at 100.0 °C were dropped into 510.0 mL of water at 26.70 °C. The molar heat capacities of iron and gold are 25.19 J/(mol • °C) and 25.41 J/(mol • °C), respectively. What is the final temperature of the water and pieces of metal?

Watch Solution

An insulated container is used to hold 43.40 g of water at 35.80 °C. A sample of copper weighing 14.10 g is placed in a dry test tube and heated for 30 minutes in a boiling water bath at 100.10 °C. The heated test tube is carefully removed from the water bath with laboratory tongs and inclined so that the copper slides into the water in the insulated container. Given that the specific heat of solid copper is 0.385 J/(g • °C), calculate the maximum temperature of the water in the insulated container after the copper metal is added.

Watch Solution

How much heat is needed to raise the temperature of 107.0 g of water from 36°C to 96°C?

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Calculate the heat energy released when 11.9 g of liquid mercury at 25.00°C is converted to solid mercury at its melting point. 

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If the heat of combustion for a specific compound is -1010.0 kJ/mol and its molar mass is 34.13 g/mol, how many grams of this compound must you burn to release 642.10 kJ of heat?

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A hot lump of 106.2 g of an unknown substance initially at 153.2°C is placed in 35.0 mL of water initially at 25.0°C and allowed to reach thermal equilibrium. The final temperature of the system is 53.2°C. What is the identity of the unknown substance? Assume no heat is lost to the surroundings.

Watch Solution

A 129 g metal bar requires 2.50 kJ to change its temperature from 26.5°C to 100.0°C. What is the specific heat of the metal?
Use correct number of significant digits, the tolerance is +/-1 in the 3rd significant digit.

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Two substances, A and B, initially at different temperature, come into contact and reach thermal equilibrium. The mass of substance A is 6.43 g and the initial temperature is 20.1°C. The mass of substance B is 25.0 g and the initial temperature is 52.1°C.  The final temperature of both substances at thermal equilibrium is 46.6°C.

Part A

If the specitic heat capacity of substance B is 1.17 J/s°C, what is the specfic heat capacity of substance A? Express your answer using two significant figures.

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You may want to reference (3 pages 349-355) section 10.4 while completing this problem.

An unknown mass of each of the following substances, initially at 23.0°C absorbs 1560 J of heat. The final temperature is recorded as indicated. Find the mass of each substance.

Part C

ethanol (Tf = 44.4°C)

Express your answer using two significant figures

Part C

water (Tf = 32.2°C)

Express your answer using two significant figures

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A silver block, initially at 56.1°C is submerged into 1000 g of water at 24.2°C, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 26.3°C.

Part A 

What is the mass of the silver block? 

Express your answer to two significant figures and include the appropriate units. 

Watch Solution

You may want to reference ( pages 349-355) section 10.4 while comparing this problem.

An unknown mass of each of the following substances, initially at 23°C, absorbs 1980 J of heat. The final temperature is recorded as indicated. Find the mass of each substance.

Part C

ethanol (T= 44.4°C) 

Express your answer using two significant figures. 

water (Tf = 32.2°C) 

Express your answer using two significant figures.

Watch Solution

You may want to reference ( pages 349-355) section 10.4 while comparing this problem.

An unknown mass of each of the following substances, initially at 230°C, absorbs 1980 J of heat. The final temperature is recorded as indicated. Find the mass of each substance

Part A 

a Pyrex glass (Tf = 553°C) 

Express your answer using two significant figures.  

Part B 

sand (Tf = 621°C) 

Express your answer using two significant figures ○Type here to searo,

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When a solid dissolves in water, heat may be evolved or absorbed. The heat of dissolution (dissolving) can be determined using a coffee cup calorimeter. 

In the laboratory a general chemistry student finds that when 3.50 g of CuSO4 (s) are dissolved in 115.90 g of water, the temperature of the solution increases from 24.19 to 27.48°C. 

The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.78 J/°C. 

Based on the student's observation, calculate the enthalpy of dissolution of CuSO4 (s) in kJ/mol. 

Assume the specific heat of the solution is equal to the specific heat of water. 

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When a 8.00-g sample of RbBr is dissolved in water in a calorimeter that has a total heat capacity of 4.816 kJ • K-1, the temperature decreases by 0.220 K. Calculate the molar heat of solution of RbBr.

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In a constant-pressure calorimeter, 70.0 mL of 0.840 M H2S04 was added to 70.0 mL of 0.460 M NaOH. The reaction caused the temperature of the solution to nse for 24.38°C - to 27.51°C. If the solution has the same density and specific heat as water (1.00 g/mL and 4.184 J/g • K, respectively), what is ΔH for this reaction (per mole of H2O produced)? Assume that the total volume is the sum of the individual volumes.

Watch Solution

 The temperature of an object increases by 42.4°C when it absorbs 3833 J of heat. Calculate the heat of the object. 

The mass of the object is 377 g.

Use this table of specific heats to identify the object.

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How much heat energy is required to raise the temperature of 0.358 kg of copper from 23.0°C to 60.0°C? The specific heat of copper is 0.0920 cal/(g • °C). Express your answer with the appropriate units.

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If 125 cal of heat is applied to a 60.0-g piece of copper at 22.0°C, what will the final temperature be? The specific heat of copper is 0.0920 cal/(g • °C). Express your answer with the appropriate units.

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Part A

Some homes that use baseboard heating use copper tubing. Hot water runs through and heats the copper tubing, which in turn heats aluminum fins is actually the aluminum fins that heat air rising through the fins. 

How much energy would it take to heat a section of the copper tubing that weighs about 505.0 g, from 13.33°C to 22.38°C ? Copper has a specific heat of 0 3850 J/g • °C). 

Express your answer to four significant figures. 

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Part C

Typically, water runs through the baseboard copper tubing and, therefore, fresh hot water is constantly running through the piping. However, consider a pipe where was allowed to sit in the pipe. The hot water cools as it sits in the pipe. What is the temperature change. (ΔT), of the water if 202.0 g of water sat in the copper pipe from part A, releasing 1760. J of the pipe. The specific heat of water is 4.184 J/(g •°C). 

Express your answer to four significant figures.

Watch Solution

When a 6.50-g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup calorimeter (the following Figure), the temperature rises from 21.6 degree C to 37.8°C. 

Calculate ΔH (in kJ/mol NaOH) for the solution process 

NaOH(s) → Na(aq) + OH- (aq) 

Assume that the specific heat of the solution is the same as that of pure water.

Express your answer with the appropriate units.

Watch Solution

When 48.0 J of heat are added to 13.2 g of a liquid, its temperature rises by 1.78°C. 

What is the heat capacity of the liquid?

Watch Solution

If you combine 280.0 mL of water at 25.00°C and 120.0 mL of water at 95.00°C, what is the final temperature of the mixture? Use 1.00 g/mL as the density of water. 

_____°C 

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In the following experiment, a coffee-cup calorimeter containing 100 mL of H 2O is used. The initial temperature of the calorimeter is 23.0°C. If 9.50 g of CaCl2 is added to the calorimeter, what will be the final temperature of the solution in the calorimeter? The heat of solution ΔHsoln of CaCl2 is -82.8 kJ/mol. 

Express your answer with the appropriate units.

Watch Solution

The complete combustion of 0. 731g of a snack bar in a calorimeter (C cal = 6.15 kJ/°C) raises the temperature of the calorimeter by 1.47°C. Calculate the food value (in Cal/g) for the snack bar.

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A researcher studying the nutritional value of a new candy places a 4.60-gram sample the candy inside a bomb calorimeter and combusts it in excess oxygen. The observed temperature increase is 2.81°C. If the heat capacity of the calorimeter is 38.20 kJ • K-1, how many nutritional Calories are there per gram of the candy?

Watch Solution

When Karl Kaveman adds chilled grog to his new granite mug, he removes 10.9 kJ of energy from the mug. If it has a mass of 625 g and was at 25°C, what is its new temperature? 

Specific heat capacity of granite = 0.79 J/g • °C. 

A. 3 °C 

B. 14 °C 

C. 22 °C 

D. 47 °C 

E. None of these choices is correct.

Watch Solution

The specific heat of a certain type of metal is 0.128 J/(g • °C). What is the final temperature if 305 J of heat is added to 43.4 g of this metal initially at 20.0°C?

Watch Solution

Why is it reasonable to assume the specific heats of NaOH and HCl solutions are the same as water, 4.18 J/g•°C?

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A pure sample of pure (E)-2, 5-dimethyl-3-hexene (C 8H16) is combusted in a bomb calorimeter. 

If the combustion of 0.871 g of (E)-2, 5-dimethyl-3-hexene results in a rise in temperature from 25.66°C to 32.77°C, what is the heat capacity (in kJ/K) of the calorimeter? Report your answer to three significant figures. 

The heat of combustion for (E)-2, 5-dimethyl-3-hexene is -5275.50 kJ/mol.

Watch Solution

The temperature of a sample of iron increased by 27°C when 261 J of heat was applied. What is the mass of the sample? 

Watch Solution

An 80.0-gram sample of a gas was heated from 25°C to 225°C. During this process, 346 J of work was done by the system and its internal energy increased by 7435 J. What is the specific heat of the gas? 

Watch Solution

The specific heat of aluminum is 0.900 J/g • °C. How many joules of heat are absorbed by 15.0 g of Al if it is heated from 20.0°C to 60.0°C x 104

a. 270 J

b. 2.40 J

c. 540 J

d. 812 J

e. 0.000117 J 

Watch Solution

The heat capacity of an object indicates how much energy that object can absorb for a given increase in that objects temperature. In a system in which two objects of different temperatures come into contact with one another, the warmer object will cool and the cooler object will warm up until the system is at a single equilibrium temperature. 

Note the difference between the terms molar heat capacity, which has units of J/(mol • °C), and specific heat, which has units of J/(g • °C). 

A volume of 110. mL of H2O is initially at room temperature (22.00 °C). A chilled steel rod at 2.00 °C is placed in the water. If the final temperature of the system is 21.40 °C, what is the mass of the steel bar? 

Use the following values: 

specific heat of water = 4.18 J/(g • °C) 

specific heat of steel = 0.452 J/(g • °C) 

Express your answer to three significant figures and include the appropriate units.

Watch Solution

A piece of cobalt with a mass of 4.28 grams is heated to raise its temperature from 22.1°C to 225.7°C. 

(a) What quantity of heat (in joules) is absorbed by the cobalt? 

(b) Determine the molar heat capacity of cobalt.

Watch Solution

A 42.41 g sample of a substance is initially at 24.4°C. After absorbing 2839 J of heat the temperature of the substance is 191.3°C. What is the specific heat (SH) of the substance?

Watch Solution

The specific heat of a certain type of metal is 0.128 J/(g•°C). What is the final temperature if 305 J of heat is added to 41.4 g of this metal initially at 20.0°C?

Watch Solution

At 1 atm, how much energy is required to heat 79.0 g of H 2O(s) at -18.0°C to H 2O(g) at 163.0°C? Helpful constants can be found here.


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When a 6.50 g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup calorimeter (the following Figure), the temperature rises from 21.6°C to 37.8°C.

Calculate ΔH (in kJ/mol NaOH) for the solution process 

NaOH(g) → Na+(aq) + OH-(aq) 

Assume that the specific heat of the solution is the same as that of pure water. 

Express your answer with the appropriate units.

Watch Solution

What is the sign and magnitude of q when 21.6 g of liquid water at 27 °C cools and freezes to form ice at -13 °C? The freezing point of water is 0°C and Cw H2O(l) = 75.4 J/mol°C.  Express your answer with the appropriate units.

Watch Solution

The following equation is the balanced combustion reaction for C6H6

2C6H6(l) + 15O2(g) → 12CO2(g) + 6H2O(l) + 6542 kJ

If 8.800 g of C6H6 is burned and the heat produced from the burning is added to 5691 g of water at 21 °C, what is the final temperature of the water?

Watch Solution

An 80.0-gram sample of a gas was heated from 25°C to 225°C. During this process. 346 J of work was done by the system and its internal energy increased by 6565 J. What is the specific heat of the gas?

Watch Solution

A 30.83 g sample of a substance is initially at 21.3°C. After absorbing 1733 J of heat, the temperature of the substance is 106.2°C. What is the specific heat (c) of the substance?

Watch Solution

Calculate the heat capacity of a calorimeter if the combustion of 5.000 g of benzoic acid led to a temperature increase of 16.573°C. The heat of combustion of benzoic acid is -26.38 kJ/g.

Watch Solution

A 428 g iron weight is added to 425 ml of water in a calorimeter at 22.6. The final temperature of the water was measured as 43.8. What was the initial temperature of the iron weight (assuming a perfectly insulated calorimeter)? You may omit units since the degree symbol cannot be included. The specific heat of iron is 0.449 J/(g * °C) and that of water is 4,184 J/(g ° C).

Watch Solution

Suppose you place 0.0300 g of magnesium chips in a coffee-cup calorimeter and then add 100 0 ml. of 1.00 M HCl. The reaction that occurs is

Mg(s) + 2 HCl(aq) → H2(g) + MgCl2(aq)

The temperature of the solution increases from 22.56 degree C (295.71 K) to 23.91 °C (297.06 K). What is the enthalpy change for the reaction per mole of Mg? Assume a specific heat capacity of the solution is 4.20 I/g • K and the density of the HCI solution is 1.00 g/mL. kJ/mol

Watch Solution

How much energy must be transferred to raise the temperature of a cup of coffee (250. mL) from 20.0 degree C (293.35 K) to 98.4 °C (371.55 K)? Assume that water and coffee have the same density (1.00 g/mL) and specific heat capacity (4 184 J/g •K).

Watch Solution

The heat capacity of an object indicates how much energy that object can absorb for a given increase in that Use the following values: object's temperature. In a system in which two objects of specific heat of water 4.18 J/(g.°C) different temperatures come into contact with one another, the warmer object will cool and the cooler object specific heat of steel 0.452 J/(g C) will warm up until the system is at a single equilibrium temperature.

Note the difference between the terms molar heat capacity, which has units of J/(mo C), and specific heat, which has units of J/(g. C).
A volume of 125 mL of H2O is initially at room temperature (22.00 C), A chilled steel rod at 2.00 C is placed in the water. If the final temperature of the system is 21.10C, what is the mass of the steel bar?

The specific heat of water is 4.18 J/(g. C). Calculate the molar heat capacity of water.

Express your answer to three significant figures and include the appropriate units.

°

Watch Solution

661 cal of heat is added to 5.00 g ice at -20.0 °C. What is the final temperature of the water? 


Watch Solution

When a 2.331-g sample of a new organic material was combusted in a bomb calorimeter, the temperature of the calorimeter (and its contents) increased from 23.89  C to 28.30 C. If the heat capacity (calorimeter constant) of the calorimeter is 31.45 kJ/ C, what is the heat of combustion per gram of the material?



Watch Solution

Enter your answer in the provided box. A 595-g piece of copper tubing is heated to 89.5 C and placed in an insulated vessel containing 159 g of water at 22.8 C. Assuming no loss of water and a heat capacity for the vessel of 10.0 J/C, what is the final temperature of the system (c of copper = 0.387 J/g  C)? 



Watch Solution

A 31.5 g water of pure gold initially at 69.3 degree C is submerged into 63.9 g of water at 27.6 degree C in an insulated container. What is the final temperature of both substances at thermal equilibrium?



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A volume of 110 mL of H_2O is initially at room temperature (22 00 degree C) A chilled steel rod at 2 00 degree C is placed n the water. If the final temperature of the system is 21.10 degree C, what is the mass of the steel bar?
Use the following values specific heat of water = 4.18 J/(g middot degree C) specific heal of steel = 0.452 J/(g middot degree C) Express your answer to three significant figures and include the appropriate units.

Watch Solution

The combustion of how many moles of ethane (C2H6) would be required to heat 884 g of water from 25.0 C to 98.0 C? (Assume liquid water is formed during the combustion.) 


Watch Solution

Exactly 132.6 J will raise the temperature of 10.0 g of a metal from 25.0  C to 60.0 ºC. What is the specific heat capacity of the metal?

a. 0.379 J/g -C
b. 2.64 J/g - C
c. 23.2 J/g - C
d. 31.7 J/g -C
 e. none of these


Watch Solution

A 2.90 g lead weight, initially at 11.1 ºC, is submerged in 7.64 g of water at 51.8 ºC in an insulated container. You may want to reference section 10.4 while completing this problem. What is the final temperature of both the weight and water at thermal equilibrium? Express the temperature in Celsius to three significant figures.


Watch Solution

A calorimeter was used to measure the heat change when an ionic compound dissolves in water. The final mass of the contents of the calorimeter was 50.73 g and the change in temperature was 2.35 ºC.

Calculate the heat change of the calorimeter contents, given that its specific heat is 4.10 J (g ºC).

Calculate the heat change of the calorimeter.

Calculate the heat change of the solution process.


Watch Solution

A 54.0 g block of an unknown metal is heated in a hot water bath to 100.0 C. When the block is placed in an insulated vessel containing 130.0 g of water at 25.0 C, the final temperature is 28.0 C. Determine the specific heat of the unknown metal. The Cs for water is 4.18 J/g-C.

Watch Solution

Consider the following reaction.

2 HCl(aq) + Ba(OH)2(aq) → BaCl2(aq) + 2H2O(l)       ΔH = -118 kJ

Calculate the heat when 102.4 mL of 0.500 M HCl is mixed with 300.0 mL of 0.410 M Ba(OH)  2. Assuming that the temperature of both solutions was initially 25.0°C and that the final mixture has a mass of 402.4 g and a specific heat capacity of 4.18J/°C·g, calculate the final temperature of the mixture.

Watch Solution

The specific heat of methanol is 2.5104 J/g.ºC. How many kJ are necessary to raise the temperature of 2.00 L of methanol from 14.0C to 30.0°C? The density of methanol is 0.7915 g/mL.

 

Watch Solution

A sample of steam with a mass of 0.510 g and at a temperature of 100°C condenses into an insulated container holding 4.50 g of water at 2.0°C.( ΔH°vap = 40.7 kJ/mol, water = 4.18 J/g•°C) Assuming that no heat is lost to the surroundings, what is the final temperature of the mixture?

Watch Solution

At 1 atm, how much energy is required to heat 55.0g of H2O(s) at -22.0°C to H2O(g) at 123.0°C? Answer in kJ and explain in detail.

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a. What is the specific heat of liquid water?

b. What is the molar heat capacity of liquid water?

c. What is the heat capacity of 185 g of liquid water?

d. How many k J of heat are needed to raise the temperature of 10.00 kg of liquid water from 24.6° C to 46.2°C?

 

Watch Solution

The enthalpy of neutralization for the reaction of HNO3 with KOH is given below.

HNO3 (aq) + KOH (aq) → H2O (l) + KNO3 (aq)    ΔH = -57.0 kJ

102.4 ml of 0.662 M HNO3 is combined with 102.4 ml of 0.662 M KOH in a coffee cup calorimeter. Both of the starting solutions were initially at a temperature of 30.64 °C. The density of each solution is 1.00 g/ml. Calculate the final temperature of the solution in the calorimeter (in °C).

Watch Solution

How many kJ of heat are needed to raise the temperature of 11.00 kg of liquid water from 24.6 C to 46.5 C?

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What is the heat capacity of 155 g of liquid water?

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What is the molar heat capacity of liquid water? Express your answer using four significant figures.

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Liquid sodium is being considered as an engine coolant. How many grams of liquid sodium (minimum) are needed to absorb 3.10 MJ of energy (in the form of heat) if the temperature of the sodium is not to increase by more than 10.0. Use Cm = 30.8 J/(K·mol) for Na(l).

Watch Solution

Liquid sodium is being considered as an engine coolant. How many grams of liquid sodium (minimum) are needed to absorb 5.90 MJ of energy (in the form of heat) if the temperature of the sodium is not increase by more than 10.0 degrees Celsius?

Use Cp=30.8J/(K*mol) for Na(l) at 500K.

Watch Solution

5.00 moles of an ideal gas are contained in a cylinder with a constant external pressure of 1.00 atm and at a temperature of 593 K by a movable, frictionless piston. This system is cooled to 504 K.

i) Calculate the work done on or by the system.

 

 

 

ii) Given that the molar heat capacity (C) of an ideal gas is 20.8 J/mol K, calculate q (J), the heat that flows into or out of the system. 

Watch Solution

The specific heat of water is 4.184 J/g °c and that of aluminum is .89 J/g °c. Will 1 gram of water or 1 gram of aluminum have the biggest increase in temperature upon the addition of 4.184 J? Explain.

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A 2.78g lead weight, initially at 11.0°C, is submerged in 7.66g of water at 52.3°C in an insulated container. What is the final temperature of both the weight and the water at thermal equilibrium?

Watch Solution

The specific heat of water is 4.18 J/(g • °C). Calculate the molar heat capacity of water. A volume of 115 mL of H2O is initially at room temperature (22.00 °C). A chilled steel rod at 2.00 °C is placed in the water. If the final temperature of the system is 21.10 °C , what is the mass of the steel bar? Specific heat of water = 4.18 J/(g • °C) specific heat of steel = 0.452 J/(g • °C).

Watch Solution

Which one of the following statements is correct?

A) The SI unit of specific heat capacity is calories per gram (cal/g)

B) Specific heat capacity is a positive value for liquids and a negative value for solids

C) When heat is transferred from the surrounding to the system q is negative

D) The larger the heat capacity of an object the more thermal energy it can store

E) Heat is transformed from the systems to the surroundings in an endothermic process

Watch Solution

If you have 340.0 mL of water at 25.00 °C and add 120.0 mL of water at 95.00 °C, what is the final temperature of the mixture? Use 1.00 g/mL as the density of water.

Watch Solution

Potassium nitrate, KNO3, has a molar mass of 101.1 g/mol. In a constant-pressure calorimeter, 32.3 g of KNO3 is dissolved in 243 g of water at 23.00 °C.

KNO3(s)+H2O(aq) ---> KOH(aq)+HNO3(aq)

The temperature of the resulting solution decreases to 17.90 °C. Assume the resulting solution has the same specific heat as water, 4.184 J/(g·°C), and that there is negligible heat loss to the surroundings.

1. How much heat was released by the solution?

2. What is the enthalpy of the reaction?

Watch Solution

Sucrose (table sugar) has the formula C12H22O11 (molar mass = 342.30 g/mol) and a food value of 6.49 kJ/g. Determine the calorimeter constant of the calorimeter in which the combustion of 0.995 g of sucrose raises the temperature by 4.21 degrees celsius (answer must be in kJ/degrees celsius).

Watch Solution

A 46.0 g sample of a metal is heated to 95.0°C and then placed in a calorimeter containing 120.0 g of water (c = 4.18 J/g°C) at 21.6°C. The final temperature of the water is 24.5°C. Which metal was used?

Watch Solution

A 2.78g lead weight, initially at 11.0°C, is submerged in 7.66g of water at 52.3°C in an insulated container. What is the final temperature of both the weight and the water at thermal equilibrium?

Watch Solution

The specific heat of water is 4.18 J/(g⋅C). Calculate the molar heat capacity of water.

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Suppose a 50.0 g block of silver (specific heat = 0.2350 J/g.°C.) at 100°C is placed in contact with a 50.0 g block of iron (specific heat = 0.4494 J/g.°C.) at 0°C, and the two blocks are insulated from the rest of the universe. The final temperature of the two blocks.

a) will be higher than 50°C.

b) will be lower than 50°C.

c) will be exactly 50°C.

d) is unrelated to the composition of the blocks.

e) cannot be predicted.

Watch Solution

Calculate q (in kJ) when 2.00 g of water is heated from 37°C to 47°C. The specific heat capacity of water is 4.184 J/g.°C.

Watch Solution

Determine the final temperature when a 25.0 g piece of iron at 85.0°C is placed into 75.0 g of water at 20.0°C. The heat capacity of the iron is 0.450 J/g °C. 

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When 1.550 g of liquid hexane (C6H14) undergoes combustion in a bomb calorimeter, the temperature rises from 25.87 to 38.13 °C. Find the ∆Erxn in kJ/mol of hexane. The heat capacity of the bomb calorimeter was found in a different experiment to be 5.73 kJ/°C. 

Watch Solution

A chemistry student weighs a rock and finds its mass to be 4.7 g. She then finds that upon absorption of 57.2 J of heat, the temperature of the rock rises from 25°C to 57°C. Find the specific heat capacity of the substance composing the rock. 

Watch Solution

The combustion of toluene has a ∆Erxn of -3.91 x 103 kJ/mol. When 1.55 g of toluene (C7H8) undergoes combustion in a bomb calorimeter, the temperature rises from 23.12 °C to 37.57 °C. Find the heat capacity of the bomb calorimeter. 

Watch Solution

Which of the following statements are correct?

A. specific heat capacity is defined as the amount of heat energy required to raise the temperature of an object 1K

B. under conditions of constant pressure, no work is done on or by the system

C. molar heat capacity is defined as the amount of heat energy required to raise the temperature of 1 mole of a substance 1K

D. heat is always transferred from an object with a lower temperature to an object with a higher temperature

Watch Solution

NOTE: YOUR ANSWER SHOULD BE IN KJ/Mol

When 0.535 g of compound X is burned completely in a bomb calorimeter containing 3000 g of water, a temperature rise of 0.363C is observed. What is ∆Urxn for the combusion of compound X? The hardware component of the calorimeter has a heat capacity of 3.51 kJ/C. The specific heat of water is 4.184 J/g ·C, and the MW of X is 56.0 g/mol.

1. -426.066

2. -610.296

3. -1074.21

4. -898.352

5. -988.425

6. -760.514

7. -589.893

8. -487.428

9. -927.731

10. -875.701

Watch Solution

How much heat is absorbed by a pan made of iron, with a mass of 150 g whose temperature rises from 25.0°C to 100.0°C?

Watch Solution

Given the following balanced equation,

2 Na(s) + 2 H2O(l) → 2 NaOH(aq) + H2(g)               ∆Hrxn = −368.4 kJ

which statement(s) is/are True?    

 

I) The reaction is endothermic.

II) The heat associated for reacting 1 mole of H 2O(l) is −184.2 kJ.

III) The temperature of the solution increases when the reaction is carried out in a coffee-cup calorimeter.

 

A) I only      

B) II only     

C) III only         

D) both I and II         

E) both II and III

Watch Solution

When 75.4 J of energy is absorbed by 0.25 mol of CCl 4, what is the temperature change of CCl4? The specific heat capacity of CCl 4 is 0.861 J/g·°C. Molar mass of CCl 4 is 153.81 g/mol.

A) 17.8°C           

B) 21.9°C   

C) 2.3°C        

D) 9.1°C        

E) 44.6°C

Watch Solution

When 5.50 g of Ba(s) is added to 100.00 g of water in a container open to the atmosphere, the reaction shown below occurs and the temperature of the resulting solution rises from 22.00°C to 61.16°C. If the specific heat capacity of the solution is 4.18 J/(g∙°C), calculate Δrxn for the reaction, as written.

            Ba(s) + 2 H2O(l)  →  Ba(OH)2(aq) + H2(g)              Δrxn = ?

A) –431 kJ          

B) –3.14 kJ         

C) +3.14 kJ       

D) +431 kJ          

E) –17.2 kJ

Watch Solution

To raise 232 g of an unknown liquid from 15°C to 60°C, 17.9 kJ of energy are required. What is the specific heat capacity, Cs, of the liquid?

A) 5.41 J/(g ∙ °C)        

B) 1.71 J/(g ∙ °C)        

C) 3.48 J/(g ∙ °C)        

D) 1.10 J/(g ∙ °C)

Watch Solution

Suppose a 50.0 g block of silver at 100°C is placed in contact with a 50.0 g block of iron at 0°C, and the two blocks are insulated from the rest of the universe.  The final temperature of the two blocks

 A)    will be higher than 50°C.

 B)    will be lower than 50°C.

 C)    will be exactly 50°C.

 D)    is unrelated to the composition of the blocks.

 E)    cannot be predicted.

Watch Solution

Calculate the amount of heat necessary to raise the temperature of 12.0 g of water from 15.4°C to 93.0°C.

A) 0.027 J            

B) 324 J            

C) 389 J        

D) 931 J        

E) 3,890 J

 

Watch Solution

How much heat, in kJ, is required to raise the temperature of 125 g H 2O from 24.3°C to 64.9°C? The specific heat of water is 4.18 J g-1 °C-1.

A) 21.2 kJ

B) 42.4 kJ

C) 12.7 kJ

D) 33.9 kJ

E) 523 kJ

 

Watch Solution

Calculate the amount of heat (in kJ) required to raise the temperature of a 79.0 g sample of ethanol from 298 K to 385 K. The specific heat capacity of ethanol is 2.42 J/g°C.

A) 12.9 kJ

B) 57.0 kJ

C) 73.6 kJ

D) 28.4 kJ

E) 16.6 kJ

 

Watch Solution

Calculate the amount of heat (in kJ) necessary to raise the temperature of 47.8 g benzene by 57 K. The specific heat capacity of benzene is 1.05 J/g°C

A) 2.59 kJ

B) 2.86 kJ

C) 3.85 kJ

D) 1.61 kJ

E) 16.6 kJ

 

Watch Solution

Determine the specific heat capacity of an alloy that requires 59.3 kJ to raise the temperature of 150.0 g alloy from 298 K to 398 K.

A) 4.38 J/g°C

B) 3.95 J/g°C

C) 2.29 J/g°C

D) 1.87 J/g°C

E) 2.53 J/g°C

Watch Solution

A sample of copper absorbs 43.6 kJ of heat, resulting in a temperature rise of 75°C, determine the mass (in kg) of the copper sample if the specific heat capacity of copper is 0.385 J/g°C.

A) 6.62 kg

B) 1.51 kg

C) 3.64 kg

D) 7.94 kg

E) 1.26 kg

Watch Solution

Determine the specific heat capacity of an alloy that requires 59.3 kJ to raise the temperature of 150.0 g alloy from 298 K to 398 K.

A) 3.95 J/g°C

B) 1.87 J/g°C

C) 2.29 J/g°C

D) 2.53 J/g°C

E) 4.38 J/g°C

Watch Solution

A 19.78 g piece of nickel (specific heat of nickel = 0.444 J/g  oC) was heated to 103.5 oC and then plunged into a beaker containing 87.9 grams of water at 14.7  oC. Determine the final temperature of the metal after the system attains thermal equilibrium. (the specific heat of water is 4.184 J/g oC)

A. 59.1 oC

B. 44.4 oC

C. 16.8 oC

D. 12.5 oC

E. 55.6 oC

Watch Solution

A sample of calcium carbonate [CaCO3 (s)] absorbs 45.5 J of heat, upon which the temperature of the sample increases from 21.1oC to 28.5oC. If the specific heat of calcium carbonate is 0.82 J/goC, what is the mass (in grams) of the sample?

A. 0.20
B. 5.0
C. 7.5
D. 410
e. 5.0 x 103

Watch Solution

A student constructs a "coffee cup" calorimeter that contains 83.6 grams of water, at 19.7°C, in a double cup set up with a thermometer and a cork cover. A piece of copper with a mass of 101.7 grams was heated to a certain temperature and placed in the calorimeter. Then the calorimeter was allowed to equilibrate and the thermometer recorded a temperature of 28.3 °C after the equilibration. Determine the temperature to which the copper piece was heated initially. (The specific heat of copper is 0.385 J/g °C and the specific heat of water is 4.184 J/g °C)

a. 105.1 °C

b. 85.4 °C

c. 142.0 °C

d. 29.0 °C

e. 48.5 °C

Watch Solution

Two solids of equal mass, labeled X and Y, are placed in contact with each other. Solid X  has an initial temperature of 100°C and  Solid Y has an initial temperature of 25°C. After some time, both solids are at 40°C. Which statement is correct regarding the direction of heat transfer and specific heat capacity (Assume heat transfers only between X and Y):

 

Direction of heat transfer                       Specific heat capacity

A.                From X to Y                                          X has greater heat capacity

B.                From X to Y                                          Y has greater heat capacity

C.                From Y to X                                          X has greater heat capacity

D.                From Y to X                                          Y has greater heat capacity

Watch Solution

A coffee-cup calorimeter of the type shown in Figure 5.17 contains 150.0 g of water at 25.1°C. A 121.0-g block of copper metal is heated to 100.4°C by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g•K. The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.1°C. (d) What would be the final temperature of the system if all the heat lost by the copper block were absorbed by the water in the calorimeter?

Watch Solution

A coffee-cup calorimeter of the type shown in Figure 5.17 contains 150.0 g of water at 25.1°C. A 121.0-g block of copper metal is heated to 100.4°C by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g•K. The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.1°C. (c) The difference between your answers for (a) and (b) is due to heat loss through the Styrofoam® cups and the heat necessary to raise the temperature of the inner wall of the apparatus. The heat capacity of the calorimeter is the amount of heat necessary to raise the temperature of the apparatus (the cups and the stopper) by 1 K. Calculate the heat capacity of the calorimeter in J/K.

Watch Solution

A coffee-cup calorimeter of the type shown in Figure 5.17 contains 150.0 g of water at 25.1°C. A 121.0-g block of copper metal is heated to 100.4°C by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g•K. The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.1°C. (b) Determine the amount of heat gained by the water. The specific heat of water is 4.18 J/g•K.

Watch Solution

A coffee-cup calorimeter of the type shown in Figure 5.17 contains 150.0 g of water at 25.1°C. A 121.0-g block of copper metal is heated to 100.4°C by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g•K. The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.1°C. (a) Determine the amount of heat, in J, lost by the copper block.

 

Watch Solution

A house is designed to have passive solar energy features. Brickwork incorporated into the interior of the house acts as a heat absorber. Each brick weighs approximately 1.8 kg. The specific heat of the brick is 0.85 J/g-K. How many bricks must be incorporated into the interior of the house to provide the same total heat capacity as 1.7 x 103 gal of water?

Watch Solution

A 2.200-g sample of quinone (C6H4O2) is burned in a bomb calorimeter whose total heat capacity is 7.854 kJ/°C. The temperature of the calorimeter increases from 23.44°C to 30.57°C. What is the heat of combustion per gram of quinone? Per mole of quinone?

Watch Solution

When a 9.55-g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup calorimeter (Figure 5.17), the temperature rises from 23.6°C to 47.4°C. Calculate ΔH (in kJ/mol NaOH) for the solution process

NaOH(s) → Na+(aq) + OH(aq)

Assume that the specific heat of the solution is the same as that of pure water.

 

Watch Solution

The specific heat of iron metal is 0.450 J/g-K. How many J of heat are necessary to raise the temperature of a 1.05-kg block of iron from 25.0°C to 88.5°C?

Watch Solution

Two solid objects, A and B, are placed in boiling water and allowed to come to the temperature of the water. Each is then lifted out and placed in separate beakers containing 1000 g water at 10.0°C. Object A increases the water temperature by 3.50°C; B increases the water temperature by 2.60°C. (a) Which object has the larger heat capacity?

Watch Solution

Which will release more heat as it cools from 50°C to 25°C, 1 kg of water or 1 kg of aluminum? How do you know?

 

Watch Solution

The molar heat capacity of silver is 25.35 J/mol•°C. Calculate how much energy (in kJ) it would take to raise the temperature of 15.7 g of the silver metal by 17.2 °C.  

 

Watch Solution

A 1.00 g sample of NH 4NO3 is decomposed in a bomb calorimeter. The temperature increases by 6.12°C. What is the molar heat of decomposition for ammonium nitrate?

a) -602 kJ•mol-1

b) -398 kJ•mol-1

c) 7.53 kJ•mol-1

d) 164 kJ•mol-1

Watch Solution

When a 45.0 g sample of an alloy at 100.0 °C is dropped into 100.0 g of water at 25.0 °C, the final temperature is 37.0 °C. What is the specific heat of the alloy? The specific heat of water is 4.184 J•g-1•°C-1

a) 0.423 J•g-1•°C-1

b) 1.77 J•g-1•°C-1

c) 9.88 J•g-1•°C-1

d) 48.8 J•g-1•°C-1

Watch Solution

Three separate 3.5g blocks of Al, Cu, and Fe at 25 °C each absorb 0.505 kJ of heat. Which block reaches the highest temperature? The specific heats of Al, Cu, and Fe are 0.900 J/g•°C, 0.385J/g•°C, and 0.444 J/g•°C, respectively.

a) Fe

b) Fe and Cu

c) Al and Cu

d) Al

e) Cu

Watch Solution

A student mixes 100 mL of 0.50 M NaOH with 100 mL 0f 0.50 M HCl in a Styrofoam® cup and observes a temperature increase of ΔT1. When she repeats this experiment using 200 mL of each solution, she observes a temperature change of ΔT2. If no heat is lost to the surroundings or absorbed by the Styrofoam® cup, what is the relationship between ΔT1 and ΔT2?

a) ΔT2 = 4 ΔT1

b) ΔT2 =  2 ΔT1

c) ΔT= 0.5 ΔT1

d) ΔT = ΔT1

Watch Solution

When 68.00 J of energy are added to a sample of Gallium that is initially at 25°C, the temperature rises to 38.0° C. What is the volume of the sample?

The specific heat of Gallium is 0.372 J•g -1•°C-1.

Density of Gallium is 5.904 g•cm–3.

a) 2.38 cm3

b) 4.28 cm3

c) 14.1 cm3

d) 31.0 cm3

Watch Solution

In a bomb calorimeter, reactions are carried out at:

(A) constant pressure 

(B) constant volume

(C) 1 atm pressure and 25°C

(D) 1 atm pressure and 0°C

Watch Solution

How much energy is required to change the temperature of  21.5 g Cu from 27 to 88.1 °C? The specific heat capacity of copper is 0.385 J/gK.

  1. 223 J
  2. 506 J
  3. 641 J
  4. 729 J
  5. 3.41 x 103
Watch Solution

If it takes 0.216 kJ of heat to raise the temperature of a 12.0 g piece of Al from 15.5 to 35.5 oC, what is the specific heat (J/g K) of Al?

Watch Solution

Adding water to a steel pan on a flame slows the rise in temerature of the pan, which of the following concepts does this represent?

A. Heat capacity is an intensive property

B. Heat capacity is an extensive property

C. The example does not relate to heat capacity

D. Temperature is a state function

Watch Solution

When a fresh breath of air is drawn into the lungs, it is heated by your body. Let’s assume it reaches thermal equilibrium with your body temperature of 37°C. Given the temperature, pressure, and the average molar mass of air, you could easily calculate that your breath of 0.48 L corresponds to 0.51 g of air. The specific heat of air is 1.0 J/g•°C.

I. Given that the temperature outside is 21°C, how much heat is required to take the air in your 0.48 L breath from 21°C to 37°C? 

 

 

 

 

 

II. The heat calculated in the previous question is lost every time you exhale. Assuming 15 breaths per minute, how much heat would be lost in one day by exhaling? Furthermore, assuming a daily energy intake of 8400 kJ (corresponding to 2000 food Calories), what percent of your daily energy intake is lost as heat due to exhaling during a 24 hour period?

Watch Solution

Which substance (with specific heat capacity provided) would show the smallest temperature change upon gaining 200.0 J of heat?

a) 50.0 g Al, CAl = 0.903 J/g°C

b) 50.0 g Cu, CCu = 0.385 J/g°C

c) 25.0 g granite, Cgranite = 0.79 J/g°C

d) 25.0 g Au, CAu = 0.128 J/g°C

e) 25.0 g Ag, CAg = 0.235 J/g°C

 

Watch Solution

Two aqueous solutions are both at room temperature and are then mixed in a coffee cup calorimeter. The reaction causes the teperature of the resulting solution to fall below room temperature. Which of the following statements is TRUE?

a) The products have a lower potential energy than the reactants.

b) This type of experiment will provide data to calculate ΔE rxn

c) The reaction is exothermic. 

d) Energy is leaving the system during the reaction. 

e) None of the above statements is true. 

 

 

The same reaction in a bomb and coffee-cup calorimeter :

a) will give the same value for ΔH rxn because it is the same reaction. 

b) will give the same value for ΔH rxn because both systems are identical.

c) will give the same values because both systems are at a constant pressure. 

d) will give slightly different values because the coffee-cup calorimeter will do some PV work. 

e) will give slightly different values because the bomb calorimeter will do some PV work. 

Watch Solution

A 0.3423 g sample of pentane, C5H12, was burned in a bomb calorimeter. The temperature of the calorimeter and the 1.000 kg of water contained therein rose from 20.22ºC to 22.82ºC. The heat capacity of the calorimeter is 2.21 kJ/ºC. The heat capacity of water = 4.184 J/gºC. How much heat was given off during combustion of the sample of pentane?

1) 8.8 kJ

2) -8.8 kJ

3) 16.6 J

4) 16.6 kJ

5) 3.1415 kJ

Watch Solution

The change in enthalpy (∆H) is a measure of the heat of reaction at

1) Constant temperature.

2) Constant pressure.

3) Constant volume.

4) Constant internal energy.

5) Constant entropy. 

Watch Solution

A 55.0-g piece of metal is heated in boiling water to 99.8 °C and then dropped into cool water in an insulated beaker containing 225 mL of water with an initial temperature of 21.0 °C. The final temperature of the metal and water is 23.1 °C, what is the specific heat capacity of the metal?

Watch Solution

How much energy must be transferred to raise the temperature of a cup of coffee that is 250 mL from 20.5 °C to 368.8 K? Assume that water and coffee have the same density 1.00 g/mL and specific heat capacity (4.184 J/g•K).

Watch Solution

Which of the following substances (with specific heat capacity provided) would show the greatest temperature change upon absorbing 100.0 J of heat?

a) 10.0 g Ag, CAg = 0.235 J/g°C

b) 10.0 g H2O, CH2O = 4.18 J/g°C

c) 10.0 g ethanol, Cethanol = 2.42 J/g°C

d) 10.0 g Fe, CFe = 0.449 J/g°C

e) 10.0 g Au, CAu = 0.128 J/g°C

Watch Solution

The molar heat capacity of silver is 25.35 J/mol × oC . Calculate how much energy (in kJ) it would take to raise the temperature of 15.7 g of the silver metal by 17.2 oC. 

Watch Solution

It takes 75.0 J to raise the temperature of an 19.3 g piece of unknown metal from 21.0oC to 46.7oC. What is the specific heat of the metal? 

Watch Solution

Consider the following reaction:

 

C12H22O11 (s) + 12 O(g)      →       13 CO (aq) + 11 H2O (l)  

in which 25.0 g of sucrose, C12H22O11 , was burned in a bomb calorimeter with a heat capacity of 8.30 kJ / °C . The temperature inside the calorimeter increases by 27.0 °C. Calculate the change in internal energy, ΔE , for the reaction per mole of sucrose. 

Watch Solution

A total of 2.25 moles of a compound are allowed to react with water in a foam coffee cup and the reaction produces 83.1 g of solution. The addition of the compound caused the temperature of the solution to increase from 20.5 oC to 32.1 oC. What is the enthalpy of the reaction? Assume no heat is transferred or lost to the surroundings or to the foam coffee cup. The specific heat of the solution is 4.184 J/(g×oC) . 

Watch Solution

The same reaction in a bomb and coffee-cup calorimeter:

a. will give the same value of Hrxn because it is the same reaction.

b. will give the same value for Hrxn because both systems are identical.

c. will give the same values because both systems are at constant temperature.

d. will give slightly different values because the coffee-cup calorimeter will do some PV work.

e. will give slightly different values because the bomb calorimeter will do some PV work

Watch Solution

A sample of 1.67 grams of compound Y is burned completely in a bomb calorimeter which contains 2500 g of water. The temperature rises from 24.273ºC to 24.587ºC. What is ∆Urxn for the combustion of compound Y? The hardware component of the calorimeter has a heat capacity of 3.29 kJ/ºC. The specific heat of water is 4.184 J/g·ºC, and the MW of Y is 117 g/mol.

1. -344.7

2. -615.4

3. -392.1

4. -322.0

5. -302.5

6. -185.4

7. -482.0

8. -652.5

9. -278.2

10. -424.3

Watch Solution

Which substance (with specific heat capacity provided) would show the smallest temperature change upon gaining 200.0 J of heat?

a. 50.0 g Al, CAl = 0.903 J/g°C

b. 50.0 g Cu, CCu = 0.385 J/g°C

c. 25.0 g granite, Cgranite = 0.79 J/g°C

d. 25.0 g Au, CAu = 0.128 J/g°C

e. 25.0 g Ag, CAg – 0.235 J/g°C

Watch Solution

In constant-volume calorimetry, what is FALSE?

 

a. There is no work performed.

b. The total energy is measured by the change in pressure.

c. The total energy is determined only by heat.

d. The heat capacity of the calorimeter needs to be known in order to determine the heat.

e. All of the above are true.

Watch Solution

The specific heat of copper metal is 0.385 J/g K. How many joules of heat are necessary to raise the temperature of a 1.42-kg block of copper from 25.0 °C to 88.5 °C?

A) 3.47 x 104 J

B) 34.7 J

C) 2.34 x 105 J

D) 8.46 J

Watch Solution

The two aqueous solutions are not at room temperature and are then mixed in a coffee cup calorimeter. The reaction causes the temperature of the resulting solution to fall below room temperature. Which of the following statements is TRUE?

 

a. The products have a lower potential energy than the reactants.

b. This type of experiment will provide data to calculate ΔE rxn

c. The reaction is exothermic.

d. Energy is leaving the system during the reaction.

e. None of the above statements is true.

Watch Solution

A piece of metal, initially at room temperature, is heated. Neither a chemical change nor a physical change takes place. During this process what remains constant?

 

A. The density

B. The mass

C. The volume

D. All of these properties remain constant. 

Watch Solution

If three samples of silver, one with a mass of 10.0 grams, another with a mass of 50.0 grams and a third with a mass of 100.0 grams each absorb 36.3 kJ of heat which sample will experience the greatest increase in temperature?

  1. The 10.0 gram sample
  2. The 50.0 gram sample
  3. The 100.0 gram sample
  4. Each will have the same increase in temperature
  5. Depends on the starting temperature of each
Watch Solution

A piece of iron (mass = 100.0 g) at 398 K is placed in a Styrofoam coffee cup calorimeter containing 25.0 mL of water 298 K. Assuming that no heat is lost to the cup, what will be the final temperature of the water? The specific heat capacity of iron = 0.449 J/gºC.

A. 308 K

B. 328 K

C. 338 K

D. 368 K

E. 388 K

Watch Solution

A bar of hot metal is placed in water in an insulated container and the two are allowed to reach thermal equilibrium. When 1.0 kg of metal at 100°C is placed in 2.0 kg of water, the temperature water bath raises from 20°C to 25°C. What is the specific heat capacity of the metal (J/g K)?

a) 0.5

b) 1.5

c) 0.22

d) 25

e) 0.025

Watch Solution

In a calorimetry experiment a student determines the enthalpy for the reaction of magnesium with hydrochloric acid to be -430 kJ/mol. The true enthalpy for this reaction is -450 kJ/mol. Which of the following sources of error could account for this discrepancy?

a. After recording the mass, some of the magnesium was dropped on the counter

b. Some of the hot hydrogen gas escaped during the reaction.

c. The calorimeter was not tightly shut for the experiment.

d. The final temperature was recorded before the reaction was complete.

e. All of these errors would cause a falsely high value for the enthalpy

Watch Solution