Ch.12 - SolutionsWorksheetSee 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
Jules Bruno

Boiling point elevation

Boiling point represents one of our four colligative properties

Boiling point elevation formula

The equation for boiling point elevation is i multiplied by kb multiplied by m. 


i represents your Van’t Hoff factor. That’s just the number of ions your solute will breakup into. If your solute is ionic, it breaks up into ions. If your solute is covalent, then it doesn't break up into ions at all; it stays intact so i equals 1. 

If you wanna take a closer look at the Van’t Hoff factor, make sure you take a look at our chapter videos and concept videos and see how we approach calculating the Van’t Hoff factor based on a specific solute given. 

Now we’re going to say that the lower case m is molality, which represents the moles of solute divided by kilograms of solvent. 

Kb represents the boiling point constant of our solvent. 

Below, I’ve provided some common types of solvents. We have water, benzene, chloroform and ethanol. You’re not expected to memorize all of their normal boiling points as well as their boiling point constants. But for water, I would recommend you memorize those. You should know that pure water boils at 100°Celsius. All you really have to remember other than that is that its boiling point constant is 0.51°Celsuis/molality. 

How to calculate boiling point

How do we apply this formula to figuring out the boiling point of a solution? We’re going to say that the boiling point of a solution equals the boiling point of the pure solvent plus my change in boiling point. Let’s say that we found that our change in our boiling point was equal to 0.7°C once we’ve plugged these variables in. We know that water boils at a temperature of 100°C. When I add solute to the pure solvent, the boiling point goes up that’s why it’s called boiling point elevation; there’s an increase in boiling point. I would just add my change in my boiling point temperature so it equals 100.7°C. That’d be the new boiling point of my solution. 

Summary

Remember, besides boiling point, we also have freezing point, osmotic pressure and Raoult’s Law, which deals with vapor pressure, as our three other colligative properties. Remember, the colligative properties help to explain what happens to a pure solvent as I add solute to it gradually over time. It causes changes in these four colligative properties. Make sure you take a look at our chapter videos and concept videos dealing with the colligative properties and the common types of problems that usually appear when discussing these four different types of properties.


Jules Bruno

Jules felt a void in his life after his English degree from Duke, so he started tutoring in 2007 and got a B.S. in Chemistry from FIU. He’s exceptionally skilled at making concepts dead simple and helping students in covalent bonds of knowledge.


Additional Problems
The constants, Kb and Kf, used to calculate the boiling point and freezing point changes observed in solutions of nonvolatile non-electrolyte solutes (a) are dependent on the concentration of the solute (b) are dependent on the properties of the solute (c) are dependent on the properties of the solvent (d) All of these are correct. (e) None of these are correct
What mass of chloroform (CHCl 3), in grams, must be added to 3.2 kg of water to produce a solution that boils at 105 oC? The boiling point constant of water is 0.512 oC / m.  a. 6.1 x 102 g CHCl3 b. 5.3 x 102 g CHCl3 c. 4.6 x 103 g CHCl3 d. 3.7 x 103 g CHCl3 e. 5.8 x 104 g CHCl3 
Calculate the boiling point of a solution that contains 210.9 g potassiuum chlorate (KCIO3) dissolved in 825.0 g of water. The Kb of water is 0.512 oC/m A. 98.93 oC B. 101.1 oC C. 105.3 oC D. 97.8 oC E. 102.1oC
Ethanol (Kb = 0.374 °C/m) typically has a boiling point of 68 °C. What will be the new boiling point after adding 2.25 moles of CaCl2 (i=2.2) to 5556 mL of ethanol (density = 1.26 g/mL)? A. 65.34 B. 71.85 C. 68.26 D. 67.99
What is the boiling point (°C) at 1 atm of a solution containing 9.54 g of calcium chloride, CaCl2(MW = 111 g/mol), in 100.0 g of water?  Kb(H2O) = 0.512°C/m a) 100.41°C b) 101.32°C c) 102.12°C d) 103.46°C e) 104.88°C  
Determine the boiling point of a solution that contains 78.8 g of naphthalene (molar mass = 128.16 g/mol) dissolved in 722 mL of benzene (d = 0.877 g/mL). Pure benzene has a boiling point of 80.1°C and a boiling point elevation constant of 2.53°C/m. A. 2.5°C B. 82.3°C C. 80.4°C D. 2.2°C E. 82.6°C
In making a large vat of coffee, how much would the boiling point (in °C) of the water be raised by the addition of 0.2 grams of caffeine, (C8H10N4O2 a polar covalent molecule) to 5.0 L of water in making this much coffee? Ignore all the other ingredients of the coffee (except the water and the caffeine) and assume that the final amount of coffee make is 10.0 L. (Kb for water is 0.512 K kg mol-1). a. 0.0001 b. 0.05 c. 0.00005 d. 0.001 e. 0.0005
Barbiturates are synthetic drugs used as sedatives and hypnotics. Barbital (MW = 184.2 g/mol) is one of the simplest of these drugs. What is the boiling point of a solution prepared by dissolving 42.5 g of barbital in 825 g of acetic acid? [Kb = 3.07°C/m, boiling point of pure acetic acid = 117.9°C] A) 117.0°C B) 117.7°C C) 118.1°C D) 118.8°C E) >120°C
What is the boiling point of a solution of 0.150 mole Al(NO3)3 in 0.500 kg water? Kb of water is 0.512 °C/m and the boiling point of water is 100.00°C A) 100.15 °C B) 100.61 °C C) 99.85 °C D) 101.50°C E) 99.39°C
Suppose you want to cook pasta and the water is boiling at 100.0°C. There is exactly one liter of water in the pot. How much salt (NaCl) in grams would you have to add to make the water boil at 103.0°C? (Kb for water is 0.512°C m -1) a) 342 b) 171 c) 85 d) 43 e) 26
You wish to increase the boiling point of water to 105°C by adding lithium fluoride to 125. mL of water. How much lithium fluoride must you add to the water? Assume the density of the water was 1.00 g/mL when the lithium fluoride was added; the Kb for water is 0.512°C/m. a) 15.8 g b) 31.6 g c) 63.3 g d) 45.9 g e) Impossible, the boiling point decreases with the addition of lithium fluoride.
Determine the boiling point of a solution that contains 78.8 g of naphthalene (C 10H8, molar mass = 128.16 g/mol) dissolved in 722 mL of benzene (d = 0.877 g/mL).  Pure benzene has a boiling point of 80.1°C and a boiling point elevation constant of 2.53°C/m. A) 2.2°C       B) 82.6°C       C) 80.4°C       D) 2.5°C       E) 82.3°C
Calculate the boiling point of an aqueous AlCl 3 solution when 72.3 g AlCl 3 are dissolved in 1320 g of water. Kb = 0.512 oC/m. (MW of AlCl3 is 133.339 g/mol).
A 100.0-mL aqueous sodium chloride solution is 14.0% NaCl by mass and has a density of 1.12 g/mL.What mass of solute would you add to make the boiling point of the solution 104.5 oC? (Use i = 1.8 for NaCl)
When 13.62 g (about one tablespoon) of table sugar (sucrose, C12H22O11) is dissolved in 241.5 mL of water (density 0.997 g/mL), the final volume is 250.0 mL (about one cup).Calculate the expected boiling point for the solution.
When 13.62 g (about one tablespoon) of table sugar (sucrose, C12H22O11) is dissolved in 241.5 mL of water (density 0.997 g/mL), the final volume is 250.0 mL (about one cup).If you had to bring this syrup to the boiling point for a recipe, would you expect it to take much more time than it takes to boil the same amount of pure water? Why or why not?
A glucose solution contains 71.8 g of glucose (C6H12O6) in 471 g of water.Determine the boiling point of the solution.
Calculate the freezing point and boiling point of a solution containing 15.2 g of naphthalene (C10H8) in 111.0 mL of benzene. Benzene has a density of 0.877 g/cm3.Calculate the boiling point of a solution. (Kb(benzene)=2.53 oC/m.)
The following diagram shows the vapor pressure curves of a volatile solvent and a solution of that solvent containing a nonvolatile solute. What are the normal boiling points of the solvent and the solution?
Determine the required concentration (in percent by mass) for an aqueous ethylene glycol (C2H6O2) solution to have a boiling point of 107.1 oC.
What is the boiling point of an aqueous solution that has a vapor pressure of 21.0 torr at 25 oC?(PH2Oo=23.78 torr; Kb = 0.512 oC/m).
A 100.0-mL aqueous sodium chloride solution is 14.0% NaCl by mass and has a density of 1.12 g/mL.What would you add (solute or solvent) to make the boiling point of the solution 104.5 oC? (Use i = 1.8 for NaCl)
The experimental boiling point of the NaCl solution is lower than that calculated assuming that NaCl is completely dissociated in solution. Why is this the case?
A solute dissolved in water causes the boiling point to increase by 0.51 oC.Does this necessarily mean that the concentration of the solute is 1.0 m?
What is the boiling point of a 0.10 M solution of NaHSO4 if the solution has a density of 1.002 g/mL?
I have decided my new hobby is going to be deep sea cooking. Step one of my first recipe is to bring water to a boil.What will the boiling point be if I am at the same depth and take Grandma's advice and add 35.9g of CaCl2 (CaCl2 = 110.98 g/mol) to my 1 kg of water? (Given that Kb for water is 0.52 oC/m)    
From your predicted value of the van't Hoff factor, calculate the boiling point of a 1.56 m aqueous solution of barium nitrate, Ba(NO3)2. The Kb of water is 0.52°C/m. _____ °C
Imagine two solutions with the same concentration and the same boiling point, but one has benzene as the solvent and the other has carbon tetrachloride as the solvent. Determine the molal concentration, m (or b), and boiling point, Tb.Given thatBenzene boiling point = 80.1          K b = 2.53Carbon tetrachloride boiling point = 76.8      K b = 5.03
What is the boiling point of an aqueous solution of 1.2 m CaCl 2?  A. 101.8 ◦CB. 103.6 ◦CC. 100.4 ◦CD. 101.2 ◦CE. 100.6 ◦C
NOTE: Glycerine is a nonelectrolyte.30.2 g of glycerine (C3H8O3, with MW 92.1 g/mol) are dissolved in 150 g of the solution. What is the new boiling point of solution?(Kb of water = 0.515°C/m)1. 101.52°C2. 1.13°C3. 101.13°C4. 0.104°C5. 100.10°C
Adrenaline is the hormone that triggers the release of extra glucose molecules in times of stress or emergency. A solution of 0.64 g of adrenaline in 36.0 g of CCl4 elevates the boiling point by 0.49 oC.Calculate the approximate molar mass of adrenaline from this data.
Calculate the boiling point of a 3.71 m aqueous sucrose solution.
Explain the following on the basis of the behavior of atoms and/or ions: CO  2(s) (dry ice) does not have a normal boiling point under normal atmospheric conditions, even though CO2 is a liquid in fire extinguishers.
What is the boiling point of 0.200 m lactose in water?
Calculate the boiling point elevation of 0.100 kg of water containing 0.010 mol of NaCl, 0.020 mol of Na2SO4, and 0.030 mol of MgCl2, assuming complete dissociation of these electrolytes.
Assuming ideal behavior, find the boiling point of a solution made by dissolving 32.8 g of calcium nitrate in 108 g of water.
Calculate the freezing point and boiling point of a solution containing 8.10 g of ethylene glycol (C2H6O2) in 92.8 mL of ethanol. Ethanol has a density of 0.789 g/cm3.Calculate the boiling point of the solution.
What is the boiling point of a solution of NaCl in water if the solution freezes at −0.93 °C?
The molar mass of a nonelectrolyte is 58.0 g/mol. Determine the boiling point of a solution containing 35.0 g of this compound and 600.0 g of water. The barometric pressure during the experiment was such that the boiling point of pure water was 99.725˚C.
A solution is prepared by dissolving 27.0 g urea, (NH2)2CO, in 150.0 g water. Calculate the boiling point of the solution. Urea is a nonelectrolyte.
Use the van't Hoff factors in the table below to calculate each colligative property:Van't Hoff Factors at 0.05 m Concentration in Aqueous SolutionSolute/Expected/MeasuredNonelectrolyte11NaCl21.9MgSO421.3MgCl232.7K2SO432.6FeCl343.4Calculate the boiling point of a 1.33 % by mass magnesium chloride solution.
An ethylene glycol solution contains 26.4 g of ethylene glycol (C2H6O2) in 92.8 mL of water. (Assume a density of 1.00 g/mL for water.)Determine the boiling point of the solution.
Consider the following solutions:0.010 m Na 3PO4 in water0.020 m CaBr 2 in water0.020 m KCl in water0.020 m HF in water (HF is a weak acid.)Assuming complete dissociation of the soluble salts, which solution(s) would have the same boiling point as 0.040 m C6H12O6 in water? C 6H12O6 is a nonelectrolyte.
What is the boiling point of a solution of 115.0 g of sucrose, C12H22O11, in 350.0 g of water?(a) Outline the steps necessary to answer the question(b) Answer the question
Using the van't Hoff factors in the table below, calculate the mass of solute required to make each aqueous solution.Van't Hoff factors at 0.05 m concentration in aqueous solutionSoluteExpectedMeasuredNonelectrolyte11NaCl21.9MgSO421.3MgCl232.7K2SO432.6FeCl343.4Calculate the mass of solute required to make an iron(III) chloride solution containing 261 g of water that has a boiling point of 108 oC.
Match the following aqueous solutions with the appropriate letter from the column on the right.1. 9.3E-2 m Al(CH3COO)3                          A.Highest boiling point2. 0.14 m (NH 4)2SO4                                  B.Second highest boiling point3. 0.23 m AgNO3                                         C.Third highest boiling point4. 0.40 m Sucrose (nonelectrolyte)             D.Lowest boiling point
The boiling point of ethanol (C2H5OH) is 78.5°C. What is the boiling point of a solution of 6.4 g of vanillin (ℳ = 152.14 g/mol) in 50.0 g of ethanol (Kb of ethanol = 1.22°C/m)?
Carbon disulfide (CS2 ) boils at 46.30 oC and has a density of 1.261 g/mL.When 0.260 mol of a nondissociating solute is dissolved in 410.0 mL of CS2, the solution boils at 47.48 oC. What is the molal boiling-point-elevation constant for  CS2?
What is the molality of NaCI formula units in an aqueous solution if the boiling point of the solution is 102.10 °C at 1 atm. (Water has a boiling point elevation constant of 0.51 °C-kg/mol.)a. 8.2 mb. 4.1 mc. 2.1 md. 0.49 m
What is the boiling point of a solution of 9.04 g of I2 in 75.5 g of benzene, assuming the I2 is nonvolatile?(a) Outline the steps necessary to answer the question.(b) Answer the question
Solution A is a 1.0 M solution with a nonionic solute and water as the solvent. Solution B is a 1.0 M solution with the same nonionic solute and ethanol as the solvent. Which solution has the greatest increase in its boiling point (relative to the pure solvent)?
A solution is made by dissolving 0.574 mol of nonelectrolyte solute in 817 g of benzene. Calculate the freezing point, Tf, and boiling point, Tb, of the solution. Constants may be found here.
Calculate the freezing point and boiling point of a solution containing 11.0 g of naphthalene (C10H8) in 116.0 mL of benzene. Benzene has a density of 0.877 g/cm3. Part ACalculate the freezing port of a solution. (Kf (benzene) = 5.12  °C/m)Part BCalculate the boiling point of a solution (Kb (benzene) = 2.53  °C/m)
Determine the boiling point of an aqueous solution that is 2.30 m ethylene glycol (C2H6O2); Kb for water is 0.52°C/m. Assume that the boiling point of pure water is 100.00°C.
At what temperature does water boil if 75.0 g of glucose (180.1 g/mol) is added to 400 g of water? 
At what temperature does water boil if 75.0 g of glucose (180.1 g/mol) is added to 400 g of water? (Use Table 12.4)a. 100.25°C b. 100.53°C c. 100.84°C d. 101.39°C e. 101.94°C
An increase in solute will ___ the boiling point of the solution.a. increaseb. decreasec. do nothing tod. neutralize