Ch.6 - Thermochemistry WorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

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 #1: Heat capacity vs. Specific Heat Capacity

Example #1: Bomb Calorimeter

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 #2: 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 ). 

Practice: 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.

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

Practice: 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?

Constant Pressure Calorimetry

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

Concept #2: Coffee Cup Calorimeter

Concept #3: Calculating the Heat of the Solution

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

Concept #4: Calculating the enthalpy of the reaction

Additional Problems
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
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. 223 J 506 J 641 J 729 J 3.41 x 103
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.    
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
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
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
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. 
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.
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
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  
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? The 10.0 gram sample The 50.0 gram sample The 100.0 gram sample Each will have the same increase in temperature Depends on the starting temperature of each
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?
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?
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
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
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
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
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.
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
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. 
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?
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. 
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. 
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. 
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
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
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
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) ΔT2 = 0.5 ΔT1 d) ΔT2  = ΔT1
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.
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
More heat is derived from cooling one gram of steam at 100°C to water at 50°C than from cooling one gram of liquid water at 100°C to 50°C because a) the steam is hotter than the water. b) the steam occupies a greater volume than the water.  c) the density of water is greater than that of steam.  d) the heat of condensation is evolved. 
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
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
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) . 
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
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. 
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
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).
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?
What is heat capacity?
Explain the difference between heat capacity and specific heat capacity.
Explain how the high specific heat capacity of water can affect the weather in coastal versus inland regions.
Spilling room-temperature water over your skin on a hot day will cool you down. Spilling vegetable oil (of the same temperature as the water) over your skin on a hot day will not. Explain the difference.
What are the units of molar heat capacity?
What are the units of specific heat?
If you know the specific heat of copper, what additional information do you need to calculate the heat capacity of a particular piece of copper pipe?
What is the specific heat of liquid water?
We pack two identical coolers for a picnic, placing 24 12-ounce soft drinks and five pounds of ice in each. However, the drinks that we put into cooler A were refrigerated for several hours before they were packed in the cooler, while the drinks that we put into cooler B were at room temperature. When we open the two coolers three hours later, most of the ice in cooler A is still present, while nearly all of the ice in cooler B has melted.Explain this difference.
Elements Compounds Substance Specific Heat (J/g-K) Substance Specific Heat (J/g-K) N2(g) 1.04 H2O(l) 4.18 Al(s) 0.90 CH4(g) 2.20 Fe(s) 0.45 CO2(g) 0.84 Hg(l) 0.14 CaCO3(s) 0.82 Table Specific Heats of Some Substances at 298 K Which substance in the table undergoes the greatest temperature change when the same mass of each substance absorbs the same quantity of heat?
Nutrition label for whole milk.Which value would change most if this label were for skim milk instead of whole milk: grams of fat, grams of total carbohydrate, or grams of protein?
Which releases the greatest amount of energy per gram when metabolized: carbohydrates, proteins, or fats?
Assuming that there is an uncertainty of 0.002 oC in each temperature reading and that the masses of samples are measured to 0.001 g, what is the estimated uncertainty in the value calculated for the heat of combustion per mole of caffeine?
What is calorimetry?
Explain the difference between a coffee-cup calorimeter and a bomb calorimeter.
Is the change in enthalpy for a reaction an extensive property?
In order to obtain the largest possible amount of heat from a chemical reaction in which there is a large increase in the number of moles of gas, should you carry out the reaction under conditions of constant volume or constant pressure?
A sample of a hydrocarbon is combusted completely in O2(g) to produce 24.01 g CO2(g), 4.917 g H2O(g), and 342 kJ of heat.Do you think that the hydrocarbon is one of those listed in Appendix C? Explain your answer.
The same reaction, with exactly the same amount of reactant, is conducted in a bomb calorimeter and in a coffee-cup calorimeter. In one of the calorimeters, qrxn = -12.5 kJ and in the other qrxn = -11.8 kJ. Which value was obtained in the bomb calorimeter? (Assume that the reaction has a positive V in the coffee-cup calorimeter.)
Coffee-cup calorimeter. This simple apparatus is used to measure temperature changes of reactions at constant pressure.Propose a reason for why two Styrofoam cups are often used instead of just one.
Bomb calorimeter.Why is a stirrer used in calorimeters?
Hess’s law provides a useful means of calculating energy changes that are difficult to measure directly. For instance, it is impossible to measure directly the enthalpy for the combustion of carbon to form carbon monoxide. Combustion of 1 mol of carbon with 0.5 mol of O2 produces both CO and CO2, leaving some carbon unreacted. However, solid carbon and carbon monoxide can both be completely burned in O2 to produce CO2.We can therefore use the enthalpy changes of these reactions to calculate the heat of combustion of carbon.What effect does this change have on Delta{ m H}: a reversing reaction?
Hess’s law provides a useful means of calculating energy changes that are difficult to measure directly. For instance, it is impossible to measure directly the enthalpy for the combustion of carbon to form carbon monoxide. Combustion of 1 mol of carbon with 0.5 mol of O2 produces both CO and CO2, leaving some carbon unreacted. However, solid carbon and carbon monoxide can both be completely burned in O2 to produce CO2.We can therefore use the enthalpy changes of these reactions to calculate the heat of combustion of carbon.What effect does this change have on Delta{ m H}: multiplying the coefficients of the equation for the reaction by 2?
Enthalpy diagram for combustion of 1 mol of methane. The enthalpy change of the one-step reaction equals the sum of the enthalpy changes of the reaction run in two steps: -890 kJ = -802 kJ + (-88 kJ).What process corresponds to the -88 kJ enthalpy change?
What is meant by the term fuel value?
Which is a greater source of energy as food, 5 g of fat or 9 g of carbohydrate?
If two objects, A and B, of different temperature come into direct contact, what is the relationship between the heat lost by one object and the heat gained by the other?
The fuel in high-efficiency natural gas vehicles consists primarily of methane CH4How much heat is produced in burning 6 mol of CH4 under standard conditions if reactants and products are brought to 298 K and H2 O(l) is formed?
Acetylene gas, C2 H2 (g), is used in welding.How much heat is produced in burning 6 mol of C2 H2 under standard conditions if both reactants and products are brought to 298 K?
Natural gas is very abundant in many Middle Eastern oil fields. However, the costs of shipping the gas to markets in other parts of the world are high because it is necessary to liquefy the gas, which is mainly methane and thus has a boiling point at atmospheric pressure of -164 oC. One possible strategy is to oxidize the methane to methanol, CH3OH, which has a boiling point of 65 oC and can therefore be shipped more readily. Suppose that 1.07×1010 ft3 of methane at atmospheric pressure and 25 oC are oxidized to methanol.Calculate the total enthalpy change for complete combustion of the 1.07×1010 ft3 of methane described above.
A coffee-cup calorimeter contains 150.0 g of water at 25.2 oC . A 123.0-g block of copper metal is heated to 100.4 oC by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g. The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.2 oC .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?
A silver block, initially at 57.6 oC, is submerged into 100.0 g of water at 24.7 oC, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 27.0 oC.What is the mass of the silver block?
A 31.5 g wafer of pure gold initially at 69.7 oC is submerged into 63.6 g of water at 27.2 oC in an insulated container.What is the final temperature of both substances at thermal equilibrium?
Two substances, A and B, initially at different temperatures, come into contact and reach thermal equilibrium. The mass of substance A is 6.23 g and its initial temperature is 20.6 oC. The mass of substance B is 25.6 g and its initial temperature is 52.5 oC. The final temperature of both substances at thermal equilibrium is 46.6 oC.If the specific heat capacity of substance B is 1.17 J/g oC, what is the specific heat capacity of substance A?
A 2.56 g sample of a substance suspected of being pure gold is warmed to 72.4 oC and submerged into 15.6 g of water initially at 24.6 oC. The final temperature of the mixture is 26.6 oC.What is the heat capacity of the unknown substance?
A 2.56 g sample of a substance suspected of being pure gold is warmed to 72.4 oC and submerged into 15.6 g of water initially at 24.6 oC. The final temperature of the mixture is 26.6 oC.Could the substance be pure gold?
A 26.0 -g aluminum block is warmed to 65.5 oC and plunged into an insulated beaker containing 55.3 g water initially at 22.2 oC. The aluminum and the water are allowed to come to thermal equilibrium.Assuming that no heat is lost, what is the final temperature of the water and aluminum?
A coffee-cup calorimeter contains 150.0 g of water at 25.2 oC . A 123.0-g block of copper metal is heated to 100.4 oC by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g. The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.2 oC .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.
To determine whether a shiny gold-colored rock is actually gold, a chemistry student decides to measure its heat capacity. She first weighs the rock and finds it has a mass of 4.0 g . She then finds that upon absorption of 54.6 J of heat, the temperature of the rock rises from 25 oC to 56 oC. Substance Specific heat capacity, Cs (J/(g oC))* Elements Lead 0.128 Gold 0.128 Silver 0.235 Copper 0.385 Iron 0.449 Aluminum 0.903 Compounds Ethanol 2.42 Water 4.18 Materials Glass (Pyrex) 0.75 Granite 0.79 Sand 0.84 * At 298 K. Find the specific heat capacity of the substance composing the rock.
To determine whether a shiny gold-colored rock is actually gold, a chemistry student decides to measure its heat capacity. She first weighs the rock and finds it has a mass of 4.0 g . She then finds that upon absorption of 54.6 J of heat, the temperature of the rock rises from 25 oC to 56 oC. Substance Specific heat capacity, Cs (J/(g oC))* Elements Lead 0.128 Gold 0.128 Silver 0.235 Copper 0.385 Iron 0.449 Aluminum 0.903 Compounds Ethanol 2.42 Water 4.18 Materials Glass (Pyrex) 0.75 Granite 0.79 Sand 0.84 * At 298 K. Determine whether the value is consistent with the rock being pure gold by referring to the table.
How much heat is required to warm 1.50 L of water from 26.0 oC to 100.0 oC? (Assume a density of 1.0/mL for the water.)
Suppose that 26 g of each of the following substances is initially at 28.0 oC. What is the final temperature of each substance upon absorbing 2.40 kJ of heat?gold
Suppose that 26 g of each of the following substances is initially at 28.0 oC. What is the final temperature of each substance upon absorbing 2.40 kJ of heat?silver
Suppose that 26 g of each of the following substances is initially at 28.0 oC. What is the final temperature of each substance upon absorbing 2.40 kJ of heat?water
A house is designed to have passive solar energy features. Brickwork is to be incorporated into the interior of the house to act as a heat absorber. Each brick weighs approximately 1.8 kg. The specific heat of the brick is 0.85 J/g.How many bricks must be incorporated into the interior of the house to provide the same total heat capacity as 1800 gal of water?
From the following data for three prospective fuels, calculate which could provide the most energy per unit volume: Fuel Density at 20oC (g/cm3) Molar Enthalpy of Combustion kJ/mol Nitroethane, C2 H5 NO2 (l) 1.052 - 1368 Ethanol, C2 H5 OH(l) 0.789 - 1367 Methylhydrazine, CH6 N2 (l) 0.874 - 1305
One tablespoon of peanut butter has a mass of 17 g . It is combusted in a calorimeter whose heat capacity is 130 kJ/oC . The temperature of the calorimeter rises from 22.3 oC to 25.5 oC.Find the food caloric content of peanut butter.
The hydrocarbons acetylene (C2 H2 ) and benzene (C6 H6 ) have the same empirical formula. Benzene is an "aromatic" hydrocarbon, one that is unusually stable because of its structure.Determine the fuel value in kJ/g for acetylene.
The hydrocarbons acetylene (C2 H2 ) and benzene (C6 H6 ) have the same empirical formula. Benzene is an "aromatic" hydrocarbon, one that is unusually stable because of its structure.Determine the fuel value in kJ/g for benzene.
Three common hydrocarbons that contain four carbons are listed here, along with their standard enthalpies of formation: Hydrocarbon Formula Hf(kJ/mol) 1,3-Butadiene C4 H6 (g) 111.9 1-Butene C4 H8 (g) 1.2 n-Butane C4 H10 (g) -124.7 For 1-Butene calculate the fuel value in kJ/g.
Three common hydrocarbons that contain four carbons are listed here, along with their standard enthalpies of formation: Hydrocarbon Formula Hf(kJ/mol) 1,3-Butadiene C4 H6 (g) 111.9 1-Butene C4 H8 (g) 1.2 n-Butane C4 H10 (g) -124.7 For n-Butane calculate the fuel value in kJ/g..
The heat of vaporization of water at 373 K is 40.7 kJ/mol.Find q for the evaporation of 451 g of water at this temperature.
An ice cube with a mass of 20 g at -20oC (typical freezer temperature) is dropped into a cup that holds 500 mL of hot water, initially at 86 oC.What is the final temperature in the cup? The density of liquid water is 1.00 g/ml the specific heat capacity of ice is 2.03 J/g-C the specific heat capacity of liquid water is 4.184 J/g-C the enthalpy of fusion of water is 6.01 kJ/mol.
The heat of vaporization of water at 373 K is 40.7 kJ/mol.Find w for the evaporation of 451 g of water at this temperature.
A sample of a hydrocarbon is combusted completely in O2(g) to produce 24.01 g CO2(g), 4.917 g H2O(g), and 342 kJ of heat.What is the mass of the hydrocarbon sample that was combusted?
What is the molar heat capacity of liquid water?
What is the heat capacity of 175 g of liquid water?
How many kJ of heat are needed to raise the temperature of 13.00 kg of liquid water from 24.5 oC to 46.5 oC?
Using information in Appendices B and C in the textbook, calculate the minimum number of grams of propane, C3H8(g), that must be combusted to provide the energy necessary to convert 5.05 kg of ice at -19.5 oC to liquid water at 75.5 oC.
A coffee-cup calorimeter contains 150.0 g of water at 25.2 oC . A 123.0-g block of copper metal is heated to 100.4 oC by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g. The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.2 oC .Determine the amount of heat, in J, lost by the copper block.
A coffee-cup calorimeter contains 150.0 g of water at 25.2 oC . A 123.0-g block of copper metal is heated to 100.4 oC by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g. The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.2 oC .Determine the amount of heat gained by the water. The specific heat of water is 4.18 J/g.
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. 
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).
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? 
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
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.
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
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  
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  
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  
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?
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. 
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.
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.
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?
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)
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 solidsC) When heat is transferred from the surrounding to the system q is negativeD) The larger the heat capacity of an object the more thermal energy it can storeE) Heat is transformed from the systems to the surroundings in an endothermic process
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?
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).
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.
What is the molar heat capacity of liquid water? Express your answer using four significant figures.
NOTE: YOUR ANSWER SHOULD BE IN KJ/MolWhen 0.535 g of compound X is burned completely in a bomb calorimeter containing 3000 g of water, a temperature rise of 0.363◦C 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. -426.0662. -610.2963. -1074.214. -898.3525. -988.4256. -760.5147. -589.8938. -487.4289. -927.73110. -875.701
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 counterb. 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
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) 0.5b) 1.5c) 0.22d) 25e) 0.025
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?
Given the following balanced equation,2 Na(s) + 2 H2O(l) → 2 NaOH(aq) + H2(g)               ∆Hrxn = −368.4 kJwhich 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
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?
If a reaction produces 1.506 kJ of heat, which is trapped in 30.0 g of water initially at 26.5°C in a calorimeter like that in Figure 5.12, what is the resulting temperature of the water?
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 processNaOH(s) → Na+(aq) + OH–(aq)Assume that the specific heat of the solution is the same as that of pure water. 
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?
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  
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 rxnc. The reaction is exothermic.d. Energy is leaving the system during the reaction.e. None of the above statements is true.
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. 
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
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? 
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?
Explain the difference between heat capacity and specific heat of a substance.
Diluting sulfuric acid with water is highly exothermic:H2SO4(l)     H2O ⟶ H2SO4(aq) + heatUse the ideas of density and heat capacity to explain why you should add acid to water rather than water to acid.
Palmitic acid (C16H32O2) is a dietary fat found in beef and butter. The caloric content of palmitic acid is typical of fats in general. Write balanced equations for the complete combustion of palmitic acid and table sugar (sucrose, C12H22O11). The standard enthalpy of formation of palmitic acid is –208 kJ/mol and that of sucrose is –2226.1 kJ/mol. [Use H2O(l) in the balanced chemical equations because the metabolism of these compounds produces liquid water.]Which dietary substance (sugar or fat) contains more Calories per gram?
Would the amount of heat absorbed by the dissolution in Example 5.6 appear greater, lesser, or remain the same if the heat capacity of the calorimeter were taken into account? Explain your answer.
Both propane and butane are used as gaseous fuels. Which compound produces more heat per gram when burned?
A 1-kg cylinder of aluminum and 1-kg jug of water, both at room temperature, are put into a refrigerator. After one hour, the temperature of each object is measured. One of the objects is much cooler than the other. Which one?
Two substances A and B, initially at different temperatures, are thermally isolated from their surroundings and allowed to come into thermal contact. The mass of substance A is twice the mass of substance B, but the specific heat capacity of substance B is four times the specific heat capacity of substance A. Which substance will undergo a larger change in temperature?
Which sample is most likely to undergo the smallest change in temperature upon the absorption of 100 kJ of heat?a) 15 g waterb) 15 g leadc) 50 g waterd) 50 g lead
Two solid objects, A and B, are placed in boiling water and allowed to come to temperature there. Each is then lifted out and placed in separate beakers containing 1000 g water at 10.0 oC. Object A increases the water temperature by 3.50 oC; B increases the water temperature by 2.60 oC.Which object has the greater heat capacity?        
Table 5.2Specific Heats of Some Substances at 298 KElementsSubstanceSpecific Heat (J/g K)N2(g)1.04Al(s)0.90Fe(s)0.45Hg(l)0.14CompoundsSubstanceSpecific Heat (J/g K)H2O(l)4.18CH4(g)2.20CO2(g)0.84CaCO3(s)0.82Which substance in Table 5.2 requires the smallest amount of energy to increase the temperature of 50.5 g of that substance by 13 K?
Four 50.0-g samples of different colorless liquids are placed in beakers at Tinitial = 25.0°C. Each liquid is heated until 450.0 J of heat has been absorbed; Tfinal is shown on each beaker below. Rank the liquids in order of increasing specific heat capacity.
Suppose you are cold-weather camping and decide to heat some objects to bring into your sleeping bag for added warmth. You place a large water jug and a rock of equal mass near the fire. Over time, both the rock and the water jug warm to about 38 oC (100 oF). If you could bring only one into your sleeping bag, which one should you choose to keep you the warmest?
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.
Consider the following reaction.2 HCl(aq) + Ba(OH)2(aq) → BaCl2(aq) + 2H2O(l)       ΔH = -118 kJCalculate 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.
A serving of a particular ready-to-serve chicken noodle soup contains 2.5 g fat, 14 g carbohydrate, and 7 g protein. According to its nutrition label, the same soup also contains 690 mg of sodium. Do you think the sodium contributes to the caloric content of the soup?
What is the change in enthalpy (∆H) for a chemical reaction?
How is ∆H different from ∆E?
Exactly 1.5 g of a fuel is burned under conditions of constant pressure and then again under conditions of constant volume. In measurement A the reaction produces 25.9 kJ of heat, and in measurement B the reaction produces 23.3 kJ of heat. Which measurement (A or B) corresponds to conditions of constant pressure?
Exactly 1.5 g of a fuel is burned under conditions of constant pressure and then again under conditions of constant volume. In measurement A the reaction produces 25.9 kJ of heat, and in measurement B the reaction produces 23.3 kJ of heat. Which one corresponds to conditions of constant volume?
Write a balanced equation and draw an enthalpy diagram for combustion of 1 mol of ethane.
Write a balanced equation and draw an enthalpy diagram for freezing of liquid water.
Would the amount of heat measured for the reaction HCl(aq) + NaOH(aq) ⟶ NaCl(aq) + H 2O(l)be greater, lesser, or remain the same if we used a calorimeter that was a poorer insulator than a coffee cup calorimeter? Explain your answer.
Would the amount of heat absorbed by the dissolution in Example 5.6 appear greater, lesser, or remain the same if the experimenter used a calorimeter that was a poorer insulator than a coffee cup calorimeter? Explain your answer.
The specific heat of octane, C8H18 (l), is 2.22 J/g K.Which will require more heat, increasing the temperature of 1 mol of C8H18 (l) by a certain amount or increasing the temperature of 1 mol of H2O (l) by the same amount?
A 100.0-g bar of gold is heated from 25 oC to 50 oC, during which it absorbs 322 J of heat. Assume the volume of the gold bar remains constant.Suppose that the same amount of heat is added to two 10.0-g blocks of metal, both initially at the same temperature. One block is gold metal, and one is iron metal. Which block will have the greater rise in temperature after the addition of the heat? (Note that the specific heat of iron is 0.451 J/g oC.)
If two objects, A and B, of different temperature come into direct contact, what is the relationship between the heat lost by one object and the heat gained by the other? What is the relationship between the temperature changes of the two objects? (Assume that the two objects do not lose any heat to anything else.)
A 500 mL bottle of water at room temperature and a 2 L bottle of water at the same temperature were placed in a refrigerator. After 30 minutes, the 500 mL bottle of water had cooled to the temperature of the refrigerator. An hour later, the 2 L of water had cooled to the same temperature. When asked which sample of water lost the most heat, one student replied that both bottles lost the same amount of heat because they started at the same temperature and finished at the same temperature. A second student thought that the 2 L bottle of water lost more heat because there was more water. A third student believed that the 500 mL bottle of water lost more heat because it cooled more quickly. A fourth student thought that it was not possible to tell because we do not know the initial temperature and the final temperature of the water. Indicate which of these answers is correct and describe the error in each of the other answers.
The reactionSO3 (g) + H2O (l) → H2SO4(aq)is the last step in the commercial production of sulfuric acid. The enthalpy change for this reaction is -227 kJ. In designing a sulfuric acid plant, is it necessary to provide for heating or cooling of the reaction mixture? Explain.
A 45 g aluminum spoon (specific heat 0.88 J/g°C) at 24°C is placed in 180 mL (180 g) of coffee at 85°C and the temperature of the two become equal.The first time a student solved this problem she got an answer of 88°C. Explain why this is clearly an incorrect answer.
Two substances, A and B, of equal mass but at different temperatures come into thermal contact. The specific heat capacity of substance A is twice the specific heat capacity of substance B. Which statement is true of the temperature of the two substances when they reach thermal equilibrium? (Assume no heat loss other than the thermal transfer between the substances.)a) The final temperature of both substances is closer to the initial temperature of substance A than the initial temperature of substance B.b) The final temperature of both substances is closer to the initial temperature of substance B than the initial temperature of substance A.c) The final temperature of both substances is exactly midway between the initial temperatures of substance A and substance B.d) The final temperature of substance B is greater than the final temperature of substance A.
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?
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?  
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.
When 1.551 g of liquid hexane (C6H14) undergoes combustion in a bomb calorimeter, the temperature rises from 25.76 oC to 38.51 oC. Find ∆Erxn for the reaction in kJ/mol hexane. The heat capacity of the bomb calorimeter, determined in a separate experiment, is 5.75 kJ/oC .
Which is the least expensive source of energy in kilojoules per dollar: a box of breakfast cereal that weighs 32 ounces and costs $4.23, or a liter of isooctane (density, 0.6919 g/mL) that costs $0.45? Compare the nutritional value of the cereal with the heat produced by combustion of the isooctane under standard conditions. A 1.0 ounce serving of the cereal provides 130 Calories.
In a coffee-cup calorimeter, 1.60 g NH 4NO3 was mixed with 75.0 g water at an initial temperature 25.00˚C. After dissolution of the salt, the final temperature of the calorimeter contents was 23.34˚C. Assuming the solution has a heat capacity of 4.18 J/g • ˚C, and assuming no heat loss to the calorimeter, calculate the enthalpy of solution (ΔHsoln) for the dissolution of NH 4NO3 in units of kJ/mol.
Explain how the heat measured in Example 5.5 differs from the enthalpy change for the exothermic reaction described by the following equation:HCl(aq) + NaOH(aq) ⟶ NaCl(aq) + H 2O(l)
Using the data in the check your learning section of Example 5.5, calculate ΔH in kJ/mol of AgNO3(aq) for the reaction: NaCl(aq) + AgNO3(aq) ⟶ AgCl(s) + NaNO 3(aq)
Calculate the enthalpy of solution (ΔH for the dissolution) per mole of NH 4NO3 under the conditions described in Example 5.6.
A coffee-cup calorimeter initially contains 125 g water at 24.2°C. Potassium bromide (10.5 g), also at 24.2°C, is added to the water, and after the KBr dissolves, the final temperature is 21.1°C. Calculate the enthalpy change for dissolving the salt in J/g and kJ/mol. Assume that the specific heat capacity of the solution is 4.18 J/°C ? g and that no heat is transferred to the surroundings or to the calorimeter.
In a coffee-cup calorimeter, 1.60 g NH4NO3 is mixed with 75.0 g water at an initial temperature of 25.00°C. After dissolution of the salt, the final temperature of the calorimeter contents is 23.34°C. Assuming the solution has a heat capacity of 4.18 J/°C ? g and assuming no heat loss to the calorimeter, calculate the enthalpy change for the dissolution of NH4NO3 in units of kJ/mol.
Consider the reaction2ClF3 (g) +  2NH3 (g) → N2 (g) + 6HF(g) + Cl2 (g)ΔH° = -1196 kJCalculate ΔHf° for ClF3(g).
You may want to reference (Pages 823 - 825)Section 19.4 while completing this problem.Isomers are molecules that have the same chemical formula but different arrangements of atoms, as shown here for two isomers of pentane, C5H12. Do you expect a significant difference in the enthalpy of combustion of the two isomers? Explain.
Quinone is an important type of molecule that is involved in photosynthesis. The transport of electrons mediated by quinone in certain enzymes allows plants to take water, carbon dioxide, and the energy of sunlight to create glucose. A 0.1964-g sample of quinone (C6H4O2) is burned in a bomb calorimeter with a heat capacity of 1.56 kJ/°C. The temperature of the calorimeter increases by 3.2°C. Calculate the energy of combustion of quinone per gram and per mole.
Syngas can be burned directly or converted to methanol. Calculate ΔH° for the reactionCO (g) + 2 H2 (g) → CH3OH (l)
Ethanol (C2H5OH) has been proposed as an alternative fuel. Calculate the standard enthalpy of combustion per gram of liquid ethanol.
Natural gas is very abundant in many Middle Eastern oil fields. However, the costs of shipping the gas to markets in other parts of the world are high because it is necessary to liquefy the gas, which is mainly methane and thus has a boiling point at atmospheric pressure of -164 oC. One possible strategy is to oxidize the methane to methanol, CH3OH, which has a boiling point of 65 oC and can therefore be shipped more readily. Suppose that 1.07×1010 ft3 of methane at atmospheric pressure and 25 oC are oxidized to methanol.Methane, when liquefied, has a density of 0.466 g/mL; the density of methanol at 25 oC is 0.791 g/mL. Compare the enthalpy change upon combustion of a unit volume of liquid methane and liquid methanol. From the standpoint of energy production, which substance has the higher enthalpy of combustion per unit volume?
Methanol (CH3OH) has also been proposed as an alternative fuel. Calculate the standard enthalpy of combustion per gram of liquid methanol, and compare this answer to that for ethanol in Exercise 87.
Natural gas is very abundant in many Middle Eastern oil fields. However, the costs of shipping the gas to markets in other parts of the world are high because it is necessary to liquefy the gas, which is mainly methane and thus has a boiling point at atmospheric pressure of -164 oC. One possible strategy is to oxidize the methane to methanol, CH3OH, which has a boiling point of 65 oC and can therefore be shipped more readily. Suppose that 1.07×1010 ft3 of methane at atmospheric pressure and 25 oC are oxidized to methanol.(A) What volume of methanol is formed if the density of CH3OH is 0.791 g/mL? (B)Calculate the total enthalpy change for complete combustion of the equivalent amount of methanol, as calculated in part A.
Consider the reactionB2H6 (g) + 3O2 (g) → B2O3 (s) + 3H2O (g)            ΔH = -2035 kJCalculate the amount of heat released when 54.0 g of diborane is combusted.
The heat of vaporization of water at 373 K is 40.7 kJ/mol. Find ΔE for the evaporation of 451 g of water at this temperature.
The heat of vaporization of water at 373 K is 40.7 kJ/mol. Find ΔH for the evaporation of 451 g of water at this temperature.
Find ΔE for the change in state of 1.0 mol H2O(l) at 81 oC to H2O(g) at 115 oC. The heat capacity of H2O(l) = 75.3 J/mol K, heat capacity of H2O(g) = 25.0 J/mol K, and the heat of vaporization of H2O is 40.7 103/mol at 100 oC.
Find ΔH for the change in state of 1.0 mol H2O(l) at 81 oC to H2O(g) at 115 oC. The heat capacity of H2O(l) = 75.3 J/mol K, heat capacity of H2O(g) = 25.0 J/mol K, and the heat of vaporization of H2O is 40.7 103/mol at 100 oC.
If the reaction to form water were writtenlarge{{ m{H}}_2 left( g ight); + ;frac{1}{2}{ m{O}}_2 left( g ight); ightarrow ;{ m{H}}_2 { m{O}}left( g ight)}, would you expect the same value of Delta{ m H} as in Equation 2: H2(g) + O2(g) → H2O(g), ΔH = –483.6 kJ?
Under constant-volume conditions the heat of combustion of benzoic acid (C6H5COOH) is 26.38 kJ/g. A 2.760 -g sample of benzoic acid is burned in a bomb calorimeter. The temperature of the calorimeter increases from 21.50 oC to 29.95 oC.A 1.460 -g sample of a new organic substance is combusted in the same calorimeter. The temperature of the calorimeter increases from 22.14 oC to 27.09 oC. What is the heat of combustion per gram of the new substance?
When a 3.80-g sample of liquid octane (C8H18) is burned in a bomb calorimeter, the temperature of the calorimeter rises by 27.1 °C. The heat capacity of the calorimeter, measured in a separate experiment, is 6.21 kJ/°C. Determine ΔE for octane combustion in units of kJ/mol octane.
When 0.515 g of biphenyl (C12H10) undergoes combustion in a bomb calorimeter, the temperature rises from 25.9°C to 30.0°C. Find ΔErxn for the combustion of biphenyl. The heat capacity of the bomb calorimeter, determined in a separate experiment, is 5.86 kJ/°C.
If 55.0 mL of ethanol (density = 0.789 g/mL) initially at 8.0˚C is mixed with 55.0 mL of water (density = 1.0 g/mL) initially at 28.5˚C in an insulated beaker, what is the final temperature of the mixture, assuming that no heat is lost? (CEtOH= 2.42 J/(g•C))      
A block of copper of unknown mass has an initial temperature of 65.1 oC. The copper is immersed in a beaker containing 95.1 g of water at 22.8 oC. When the two substances reach thermal equilibrium, the final temperature is 24.6 oC. What is the mass of the copper block? Assume that Cs, H2O = 4.18 J/(g ) and Cs, Cu = 0.385 J/(g ).
Two substances, lead and glass (Pyrex), initially at different temperatures, come into contact and reach thermal equilibrium. The mass of lead is 18.1 g and its initial temperature is 62.6˚C. The mass of glass (Pyrex) is 20.6 g and its initial temperature is 25.1˚C. What is the final temperature of both substances at thermal equilibrium? (The specific heat capacity of lead is 0.128 J/g•˚C; the specific heat capacity of glass (Pyrex) is 0.75 J/g•˚C.)
A 4.96 g sample of gold, initially at 62.6˚C, is submerged into 55.1 g of ethanol at 20.1˚C in an insulated container. What is the final temperature of both substances at thermal equilibrium? (The specific heat capacity of gold is 0.128 J/g•˚C; the specific heat capacity of ethanol is 2.42 J/g•˚C)
A 32.6 g iron rod, initially at 22.3 oC, is submerged into an unknown mass of water at 63.3 oC, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 59.1 oC.What is the mass of the water?
A 30.0-g sample of water at 280. K is mixed with 50.0 g water at 330. K. Calculate the final temperature of the mixture assuming no heat loss to the surroundings.
How many milliliters of water at 23°C with a density of 1.00 g/mL must be mixed with 180 mL (about 6 oz) of coffee at 95°C so that the resulting combination will have a temperature of 60°C? Assume that coffee and water have the same density and the same specific heat.
How much will the temperature of a cup (180 g) of coffee at 95°C be reduced when a 45 g silver spoon (specific heat 0.24 J/g°C) at 25°C is placed in the coffee and the two are allowed to reach the same temperature? Assume that the coffee has the same density and specific heat as water.
A pure gold ring and pure silver ring have a total mass of 16.0 g. The two rings are heated to 71.1 oC and dropped into a 13.6 mL of water at 21.8 oC. When equilibrium is reached, the temperature of the water is 24.2 oC. What is the mass of gold ring? (Assume a density of 0.998 g/mL for water.)
A pure gold ring and pure silver ring have a total mass of 16.0 g. The two rings are heated to 71.1 oC and dropped into a 13.6 mL of water at 21.8 oC. When equilibrium is reached, the temperature of the water is 24.2 oC. What is the mass of silver ring? (Assume a density of 0.998 g/mL for water.)
Two iron bolts of equal mass—one at 100.°C, the other at 55°C—are placed in an insulated container. Assuming the heat capacity of the container is negligible, what is the final temperature inside the container (c of iron = 0.450 J/g•K)?
One piece of copper jewelry at 105°C has twice the mass of another piece at 45°C. Both are placed in a calorimeter of negligible heat capacity. What is the final temperature inside the calorimeter (c of copper = 0.387 J/g•K)?
A biology experiment requires the preparation of a water bath at 37.0°C (body temperature). The temperature of the cold tap water is 22.0°C, and the temperature of the hot tap water is 55.0°C. If a student starts with 90.0 g cold water, what mass of hot water must be added to reach 37.0°C?
(a) How much heat is released when 25.0 g of methane burns in excess O2 to form gaseous CO2 and H2O? (b) Calculate the temperature of the product mixture if the methane and air are both at an initial temperature of 0.0°C. Assume a stoichiometric ratio of methane to oxygen from the air, with air being 21% O2 by volume (c of CO 2 = 57.2 J/mol•K; c of H 2O(g) = 36.0 J/mol•K; c of N 2 = 30.5 J/mol•K).
A 45 g aluminum spoon (specific heat 0.88 J/g°C) at 24°C is placed in 180 mL (180 g) of coffee at 85°C and the temperature of the two become equal.What is the final temperature when the two become equal? Assume that coffee has the same specific heat as water.
A 5.00-g sample of aluminum pellets (specific heat capacity = 0.89 J/°C ? g) and a 10.00-g sample of iron pellets (specific heat capacity = 0.45 J/°C ? g) are heated to 100.0°C. The mixture of hot iron and aluminum is then dropped into 97.3 g water at 22.0°C. Calculate the final temperature of the metal and water mixture, assuming no heat loss to the surroundings.
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).
Substances A and B, initially at different temperatures, come in contact with each other and reach thermal equilibrium. The mass of substance A is twice the mass of substance B. The specific heat capacity of substance B is twice the specific heat capacity of substance A. Which statement is true about the final temperature of the two substances once thermal equilibrium is reached?(a) The final temperature is closer to the initial temperature of substance A than it is to the initial temperature of substance B.(b) The final temperature is closer to the initial temperature of substance B than it is to the initial temperature of substance A.(c) The final temperature is exactly midway between the initial temperatures of substances A and B.
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?
A 2.51 g lead weight, initially at 10.6˚C, is submerged in 7.86 g of water at 52.4˚C in an insulated container. What is the final temperature of both the weight and the water at thermal equilibrium?
One method of generating electricity is by burning coal to heat water, which produces steam that drives an electric generator. To determine the rate at which coal is to be fed into the burner in this type of plant, the heat of combustion per ton of coal must be determined using a bomb calorimeter. When 1.00 g of coal is burned in a bomb calorimeter (Figure 5.17), the temperature increases by 1.48°C. If the heat capacity of the calorimeter is 21.6 kJ/°C, determine the heat produced by combustion of a ton of coal (2.000 x 103 pounds).
An unknown mass of each substance, initially at 24.0˚C, absorbs 1950 J of heat. The final temperature is recorded. Find the mass of each substance: Pyrex glass (Tf = 55.5˚C)
An unknown mass of each substance, initially at 24.0˚C, absorbs 1950 J of heat. The final temperature is recorded. Find the mass of each substance: sand (Tf = 62.2˚C)
An unknown mass of each substance, initially at 24.0˚C, absorbs 1950 J of heat. The final temperature is recorded. Find the mass of each substance: ethanol (Tf = 44.3˚C)
An unknown mass of each substance, initially at 24.0˚C, absorbs 1950 J of heat. The final temperature is recorded. Find the mass of each substance: water (Tf = 32.2˚C)
Consider the substances in Table 7‑1. Which substance requires the largest amount of energy to raise the temperature of 25.0 g of the substance from 15.0°C to 37.0°C? Calculate the energy. Which substance in Table 7‑1 has the largest temperature change when 550. g of the substance absorbs 10.7 kJ of energy? Calculate the temperature change.
The specific heat capacity of silver is 0.24 J/°C•ga. Calculate the energy required to raise the temperature of 150.0 g Ag from 273 K to 298 K.
SubstanceSpecific heatcapacity, Cs (J/(g oC))*ElementsLead0.128Gold0.128Silver0.235Copper0.385Iron0.449Aluminum0.903CompoundsEthanol2.42Water4.18MaterialsGlass (Pyrex)0.75Granite0.79Sand0.84* At 298 K.A 51 g aluminum block initially at 27.0 oC absorbs 737 J of heat. What is the final temperature of the aluminum?
In a bomb calorimeter, the reaction vessel is surrounded by water that must be added for each experiment. Since the amount of water is not constant from experiment to experiment, the mass of water must be measured in each case. The heat capacity of the calorimeter is broken down into two parts: the water and the calorimeter components. If a calorimeter contains 1.00 kg water and has a total heat capacity of 10.84 kJ/°C, what is the heat capacity of the calorimeter components?
A propane tank on a home barbeque contains 11.3x103 g of propane. Use the value for ΔHrxn provided in the text to calculate the total amount of heat produced when the entire contents of the tank of propane is burned. What mass of water could be warmed from 25˚C to 100˚C with this much heat?
The bomb calorimeter in Exercise 102 is filled with 987 g water. The initial temperature of the calorimeter contents is 23.32°C. A 1.056-g sample of benzoic acid (ΔEcomb = -26.42 kJ/g) is combusted in the calorimeter. What is the final temperature of the calorimeter contents?
Calculate the heat capacity, in joules and in calories per degree, of the following: 28.4 g of water
Calculate the heat capacity, in joules and in calories per degree, of the following: 1.00 oz of lead
Calculate the heat capacity, in joules and in calories per degree, of the following:45.8 g of nitrogen gas
Suppose that 26 g of each of the following substances is initially at 28.0 ºC. What is the final temperature of each substance upon absorbing 2.40 kJ of heat?a) aluminum
Calculate the heat capacity, in joules and in calories per degree, of the following:1.00 pound of aluminum metal
How much heat, in joules and in calories, must be added to a 75.0 g iron block with a specific heat of 0.449 J/g°C to increase its temperature from 25°C to its melting temperature of 1535°C?
How much heat, in joules and in calories, is required to heat a 28.4 g (1 oz) ice cube from −23.0°C to −1.0°C?
The specific heat capacity of silver is 0.24 J/°C•gb. Calculate the energy required to raise the temperature of 1.0 mole of Ag by 1.0°C (called the molar heat capacity of silver).
If 14.5 kJ of heat were added to 485 g of liquid water, how much would its temperature increase?
Stearic acid (C18H36O2) is a fatty acid, a molecule with a long hydrocarbon chain and an organic acid group (COOH) at the end. It is used to make cosmetics, ointments, soaps, and candles and is found in animal tissue as part of many saturated fats. In fact, when you eat meat, you are ingesting some fats containing stearic acid.Calculate the heat (q) released in kJ and kcal when 1.00 g of stearic acid is burned completely.
The specific heat capacity of silver is 0.24 J/°C•gc. It takes 1.25 kJ of energy to heat a sample of pure silver from 12.0°C to 15.2°C. Calculate the mass of the sample of silver.
The heat capacity of a bomb calorimeter was determined by burning 6.79 g methane (energy of combustion = -802 kJ/mol CH4) in the bomb. The temperature changed by 10.8°C. a. What is the heat capacity of the bomb?
A piece of unknown substance weighs 44.7 g and requires 2110 J to increase its temperature from 23.2°C to 89.6°C.If it is one of the substances found in Table 5.1, what is its likely identity?
The combustion of 0.1584 g benzoic acid increases the temperature of a bomb calorimeter by 2.54°C. Calculate the heat capacity of this calorimeter. (The energy released by combustion of benzoic acid is 26.42 kJ/g.) A 0.2130-g sample of vanillin (C8H8O3) is then burned in the same calorimeter, and the temperature increases by 3.25°C. What is the energy of combustion per gram of vanillin? Per mole of vanillin?
A piece of unknown solid substance weighs 437.2 g, and requires 8460 J to increase its temperature from 19.3°C to 68.9°C.If it is one of the substances found in Table 5.1, what is its likely identity?
A 5.00-g sample of one of the substances listed in Table 7‑1 was heated from 25.2°C to 55.1°C, requiring 133 J to do so. Which substance was it?
An aluminum kettle weighs 1.05 kg.How much heat is required to increase the temperature of this kettle from 23.0°C to 99.0°C?
An aluminum kettle weighs 1.05 kg.How much heat is required to heat this kettle from 23.0°C to 99.0°C if it contains 1.25 L of water (density of 0.997 g/mL and a specific heat of 4.184 J/g°C)?
It takes 585 J of energy to raise the temperature of 125.6 g mercury from 20.0°C to 53.5°C. Calculate the specific heat capacity and the molar heat capacity of mercury.
Use standard enthalpies of formation to calculate the standard change in enthalpy for the melting of ice. (The ΔH˚f for H2O(s) is –291.8 kJ/mol.) Use this value to calculate the mass of ice required to cool 360 mL of a beverage from room temperature (25.0˚C) to 0.0˚C. Assume that the specific heat capacity and density of the beverage are the same as those of water.
Palmitic acid (C16 H32 O2 ) is a dietary fat found in beef and butter. The caloric content of palmitic acid is typical of fats in general. Write a balanced equation for the complete combustion of palmitic acid. What is the caloric content of palmitic acid in Cal/g? The standard enthalpy of formation of palmitic acid is –208 kJ/mol and that of sucrose is –2226.1 kJ/mol. [Use H2O(l) in the balanced chemical equations because the metabolism of these compounds produces liquid water.]
A sample of nickel is heated to 99.8°C and placed in a coffeecup calorimeter containing 150.0 g water at 23.5°C. After the metal cools, the final temperature of metal and water mixture is 25.0°C. If the specific heat capacity of nickel is 0.444 J/°C ? g, what mass of nickel was originally heated? Assume no heat loss to the surroundings.
Palmitic acid (C16H32O2) is a dietary fat found in beef and butter. The caloric content of palmitic acid is typical of fats in general. Write a balanced equation for the complete combustion of table sugar (sucrose, C12H22O11). What is the caloric content of sucrose in Cal/g? The standard enthalpy of formation of palmitic acid is –208 kJ/mol and that of sucrose is –2226.1 kJ/mol. [Use H2O(l) in the balanced chemical equations because the metabolism of these compounds produces liquid water.]
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.
A 295-g aluminum engine part at an initial temperature of 13.00°C absorbs 75.0 kJ of heat. What is the final temperature of the part (c of Al = 0.900 J/g•K)?