The 4 Colligative Properties help to explain what happens to a pure solvent as solute is added to it.

Concept #1: The Colligative Properties.

The four colligative properties of Boiling Point, Freezing Point, Vapor Pressure and Osmotic Pressure will either increase or decrease with the addition of solute to a pure solvent.

Example #1: Explain what happens to each of the following properties as solute is added to a pure solvent.

**a.** Boiling Point **b.** Freezing Point

**c.** Osmotic Pressure **d.** Vapor Pressure

Example #2: Which of the following compounds will have the ** highest** boiling point?

a) 0.10 m sucrose

b) 0.10 m CsBrO_{3}

c) 0.35 m CH_{3}OH

d) 0.15 m SrBr_{2}

Example #3: Pure water boils at 100^{o}C. What is the expected boiling point of water after the addition of 13.12 g calcium bromide, CaBr_{2}, to 325 g water. K_{b} = 0.512 ^{o}C/m. **(MW of CaBr _{2} is 199.88 g/mol)**.

Example #4: The vapor pressure of water at 100.0^{o}C is 0.630 atm. Determine the amount (in grams) of aluminum fluoride, AlF_{3}, (in grams) needed to reduce its vapor pressure to 0.550 atm. **(MW of AlF _{3} is 83.98 g/mol)**.

Practice: Beta-carotene is the most important of the A vitamins. Calculate the molar mass of Beta-carotene if 25.0 mL of a solution containing 9.88 mg of Beta-carotene has an osmotic pressure of 56.16 mmHg at 30 degrees of Celsius.

Vapor Pressure is achieved by the equilibrium rate of vaporization equaling the rate of condensation.

Concept #2: Defining Vapor Pressure.

Example #5: The vapor pressure of pure liquid A is 550 torr and the vapor pressure of pure liquid B is 320 torr at room temperature. If the vapor pressure of a solution containing A and B is 465 torr, what is the mole fraction of A in the solution?

Example #6: Determine the vapor pressure lowering associated with 1.32 m C_{6}H_{12}O_{6} solution (MW: 180.156 g/mol) at 25^{o}C.

Practice: The following boiling points belong to one of the following compounds: 117^{°}C, 78^{°}C, 34.5^{°}C and 23^{°}C.

CH_{3}-O-CH_{3 }

CH_{3}CH_{2}OH

CH_{3}CH_{2}-O-CH_{2}CH_{3 }

CH_{3}CH_{2}CH_{2}CH_{2}OH

a) Which boiling point goes with what compound?

b) If each of the following substances were placed in separate sealed clear bottles at room temperature, could you identify one of the substances right away?

Calculate the vapor pressure of a solution of 7.35g of aspirin (M = 180.15 g/mol) in 37.1 g of methanol (CH3OH) at 21.2°C. Pure methanol has a vapor pressure of 101 torr at this temperature. Assume that aspirin is NOT an ionic compound.
A. 97.6 torr
B. 84.3 torr
C. 3.44 torr
D. 16.7 torr
E. 104 torr

Which of the following statements(s) is/are correct.
i. A 0.45 m BaCl2 solution will have a lower freezing point than a 0.35 m K 2CrO4 solution.
ii. A 0.35 M K2CrO4 solution will have a lower osmotic pressure than a 0.45 M BaCl 2 solution.
iii. A 0.45 m K2CrO4 solution will have a higher boiling point than a 0.45 m BaCl 2 solution.
A. i only
B. ii only
C. iii only
D. i and ii
E. ii and iii

The human eye has an osmotic pressure of 8.00 atm at 37.0 °C. What concentration (in moles/L) of a saline (NaCl) solution will provide an isotonic eyedrop solution? (Isotonic = a solution with equal osmotic pressure.)
a) 0.0785
b) 0.157
c) 0.314
d) 0.786
e) 0.942

A compound is found to have a molar mass of 598 g/mol. If 35.8 mg of the compound is dissolved in enough water to make 175 mL of solution at 25°C, what is the osmotic pressure of the resulting solution?
A. 3.42 torr
B. 6.36 torr
C. 5.01 torr
D. 5.99 torr
E. 8.36 torr

What is the vapor pressure of a solution made by dissolving 48.4 g of glucose (C6H12O6) in 202.8 g of water at 22 oC. The vapor pressure of pure water at 22 oC is 92.50 mm Hg.
A. 2.156 mm Hg
B. 74.68 mm Hg
C. 17.82 mm Hg
D. 58.81 mm Hg
E. 90.34 mm Hg

Water typically flows from a ______________solution to a ____________solution:
A. Hypertonic; hypotonic
B. Hypotonic; hypertonic
C. Isotonic; isotonic
D. Hypertonic; isotonic

What is the ideal van't Hoff factor for Mg(NO2)2?
a) 2
b) 3
c) 4
d) 6
e) 7

Identify the correct van't Hoff factors for each compound.
CaSO 4 NiHPO4 SnF 2Br2
A. 2 3 2
B. 2 2 3
C. 4 4 4
D. 5 2 5
E. 2 2 5

A 0.86% by mass solution of NaCl is called "physiological saline" because its osmotic pressure is equal to that of the solution in the blood cells. Calculate the osmotic pressure of this solution at normal body temperature (37°C). Note that the density of the saline solution is 1.005 g/mL.

The osmotic pressure of blood at normal body temperature of 37°C is 7.65 atm. Sometimes it is necessary to add a saline (NaCl) solution by intravenous injection to a patient in the emergency room. What should be the concentration of the NaCl solution (in g/L) so that it will have the same osmotic pressure as the blood at 37°C?
a. none of the other answers is even close (within 10% error)
b. 4.4
c. 2.2
d. 8.8
e. 17.6

Which statement is false?
A) The vapor pressure of a solvent over a solution decreases as its mole fraction increases.
B) The solubility of a gas increases as the temperature decreases.
C) The vapor pressure of a solvent over a solution is less than that of pure solvent.
D) The greater the pressure of a gas over a solution the greater its solubility.
E) Ionic solutes dissociate in solution causing an enhancement off all colligative properties.

The vapor pressure of pure ethanol [CH 3OH] at room temperature is 160.00 torr. What mole fraction of glycerol [C3H5(OH)3], a non volatile solute, is required to lower the vapor pressure to 86.00 torr at room temperature?
A. 0.416
B. 0.462
C. 0.538
D. 0.584

Below is a U-tube where there are equal volume solution of 0.2M NaCL and 0.1M CaCl2 seperated by a membrance that only allows water through. In which direction will there be net movement of water?
left or right

A 0.100 m MgSO4 solution has a freezing point of -0.23°C. What is the van't Hoff factor for this solution? Kf = 1.86°C/m.
A) 0.62
B) 1.0
C) 1.2
D) 2.0
E) 4.0

Identify the solute with the highest expected Van't Hoff factor.
A) AlBr 3
B) KBr
C) C 6 H 8 O 6
D) MgCl 2
E) NH 4 Cl

A solution of urea [(NH2)2CO] (MM: 60 g/mol) in water has a vapor pressure 2.50 mmHg less than that of pure water at 30°C (The vapor pressure of water at 30°C is 31.8 mmHg).
a. What is the mole fraction of urea in this solution?
b. How many grams of urea does this correspond to?

What is the expected Van’t Hoff factor for K 2CO3?
A. 1
B. 2
C. 3
D. 5
E. 6

The vapor pressure of pure acetone (CH 3COCH3) at 30°C is 240 torr. If salt (NaCl) is dissolve into a sample of acetone until the total vapor pressure of the mixture at 30°C is 180 torr, what is the mol fraction of acetone?
1. 0.2
2. 0.25
3. 0.8
4. 0.75

Kf = 1.86°C/m for water.
We observe the freezing points of four different aqueous solutions as follows:
Solution A freezes at -0.10°C
Solution B freezes at -4.00°C
Solution C freezes at -10.00°C; and
Solution D freezes at -13.00°C.
In each solution, the solute is a non-volatile non-electrolyte. Which solution should be expected to have the highest boiling point?
1. Solution D
2. Solution B
3. Solution A
4. Solution C

Water typically flows from a ______________solution to a ____________solution:
A. Hypertonic; hypotonic
B. Hypotonic; hypertonic
C. Isotonic; isotonic
D. Hypertonic; isotonic

If 2.00 mol of glucose (C 6H12O6) is dissolved in 0.500 kg of water, what is the vapor pressure of the solution? The vapor pressure of water at 25oC is 23.8 torr.
A. 23.8 torr
B. 25.5 torr
C. 8.70 torr
D. 22.2 torr
E. 1.60 torr

At 25oC the vapor pressure of pure butane (C4H10, MW = 58.12 g/mol) is p°b = 380.0 torr and the vapor pressure of pure hexane (C6H14, MW = 86.17 g/mol) is p°H = 32.0 torr. What is the total pressure at 25oC when mixing equal grams of butane and hexane?

What is the vapor pressure of a solution made by dissolving 79.3 g of glycerol (C3H8O3) in 123.8 g of water? The vapor pressure of water at 26 oC is 25.2 mmHg.
A. 9.84 mmHg
B. 15.4 mmHg
C. 2.81 mmHg
D. 22.4 mmHg
E. 3.16 mmHg

(Hint: If you dont know where to start, try assuming you have 100g total of solution.) Consider two liquids A and B. The vapor pressure of pure A (molecular weight = 50 g/mol) is 225 torr at 25°C and the vapor pressure of pure B (molecular weight = 75 g/mol) is 90 torr at the same temperature. What is the total vapor pressure at 25°C of a solution that is 25% A amd 75% B by weight?
1. 76 torr
2. 225 torr
3. 335 torr
4. 203 torr
5. 135 torr
6. 191 torr
7. 108 torr
8. 115 torr
9. 124 torr

The vapor pressure of pure water (H2O) at 30 °C is 40 torr. If salt (NaCl) is dissolved into a sample of water until the total vapor pressure of the mixture at 30 °C is 32 torr, what is the mol fraction of salt?
1. 0.2
2. 0.5
3. 0.8
4. 0.65
5. 0.35

The van't Hoff factors are a function of the concentration and are often lower than the theoretical value. Would you expect a larger or smaller deviation from the theoretical value as a solution gets more concentrated? Explain.

Red blood cells contain Na+ ions, K+ ions, and water. If we place some red blood cells into a beaker full of pure water, what will happen to them?
they will swell and burst
they will wiggle around rapidly
nothing
they will shrivel and collapse

Explain why the lower vapor pressure for a solution containing a nonvolatile solute results in a higher boiling point and lower melting point compared to the pure solvent.

What are colligative properties?

Which solution has the highest boiling point?

The osmotic pressure of 0.013 M aqueous solution of CaCl2 is found to be 0.693 atm at 25 oC.Calculate the vant Hoff factor, i, for the solution.

You may wantto reference (Pages 608 - 608) Section 13.7 while completing this problemA solution of benzene (C6H6) and toluene (C7H8) is 26.0 % benzene by mass. At 25oC the vapor pressures of pure benzene and pure toluene are 94.2 and 28.4 torr, respectively.Assuming ideal behavior, calculate the vapor pressure of benzene in the mixture.

You may wantto reference (Pages 608 - 608) Section 13.7 while completing this problemA solution of benzene (C6H6) and toluene (C7H8) is 26.0 % benzene by mass. At 25oC the vapor pressures of pure benzene and pure toluene are 94.2 and 28.4 torr, respectively.Assuming ideal behavior, calculate the total pressure above the solution.

You may wantto reference (Pages 608 - 608) Section 13.7 while completing this problemA solution of benzene (C6H6) and toluene (C7H8) is 26.0 % benzene by mass. At 25oC the vapor pressures of pure benzene and pure toluene are 94.2 and 28.4 torr, respectively.Assuming ideal behavior, calculate the mass percent of benzene in the vapor.

You may wantto reference (Pages 608 - 608) Section 13.7 while completing this problemA solution of benzene (C6H6) and toluene (C7H8) is 26.0 % benzene by mass. At 25oC the vapor pressures of pure benzene and pure toluene are 94.2 and 28.4 torr, respectively.Assuming ideal behavior, calculate the vapor pressure of toluene in the mixture.

You may wantto reference (Pages 608 - 608) Section 13.7 while completing this problemA solution of benzene (C6H6) and toluene (C7H8) is 26.0 % benzene by mass. At 25oC the vapor pressures of pure benzene and pure toluene are 94.2 and 28.4 torr, respectively.Assuming ideal behavior, calculate the mass percent of toluene in the vapor.

What is the effect of a nonvolatile solute on the vapor pressure of a liquid?
Why is the vapor pressure of a solution different from the vapor pressure of the pure liquid solvent?

You may wantto reference (Pages 608 - 608) Section 13.7 while completing this problemA solution of benzene (C6H6) and toluene (C7H8) is 26.0 % benzene by mass. At 25oC the vapor pressures of pure benzene and pure toluene are 94.2 and 28.4 torr, respectively.Why is the composition of the vapor different from the composition of the solution?

What is the effect on vapor pressure of a solution with particularly strong solute-solvent interactions?
With particularly weak solute-solvent interactions?

A beaker contains 100.0 mL of pure water. A second beaker contains 100.0 mL of seawater. The two beakers are left side by side on a lab bench for one week. At the end of the week, the liquid level in both beakers has decreased. However, the level has decreased more in one of the beakers than in the other.Which one level has decreased more?

A solution of methanol and water has a mole fraction of water of 0.312 and a total vapor pressure of 211 torr at 39.9oC. The vapor pressures of pure methanol and pure water at this temperature are 256 torr and 55.3 torr, respectively.Is the solution ideal?

At 35 oC the vapor pressure of acetone, (CH3 )2 CO, is 361
torr, and that of chloroform, CHCl3, is 301
torr. Acetone and chloroform can form weak hydrogen bonds between one another; the chlorines on the carbon give the carbon a sufficient
partial positive charge to enable this behavior:
A solution composed of an equal number of moles of acetone and chloroform has a vapor pressure of 250 torr at 35 oC.What would be the vapor pressure of the solution if it exhibited ideal behavior?

The vapor pressure of pure water at 60oC is 149 torr. The vapor pressure of water over a solution at 60 oC containing equal numbers of moles of water and ethylene glycol (a nonvolatile solute) is 67 torr. Is the solution ideal according to Raoults law?

The following diagram shows the vapor pressure curves of a volatile solvent and a solution of that solvent containing a nonvolatile solute.
Which line represents the solution?

Calculate the vapor pressure of water above a solution prepared by adding 23.0 g of lactose (C12 H22 O11 ) to 200.0 g of water at 338 K. (Vapor-pressure of water at 338 K 187.5 torr.)

Calculate the mass of propylene glycol (C3 H8 O2 ) that must be added to 0.350 kg of water to reduce the vapor pressure by 2.88 torr at 40 oC (PH2O at 40 C = 55.3).

At 63.5oC the vapor pressure of H2O is 175 torr, and that of ethanol (C2H5OH) is 400 torr. A solution is made by mixing equal masses of H2O and C2H5OH.Assuming ideal-solution behavior, what is the vapor pressure of the solution at 63.5oC?

Calculate the vapor pressure at 25 oC of an aqueous solution that is 5.55 %
NaCl by mass.

An aqueous CaCl2 solution has a vapor pressure of 82.1 mmHg at 50 oC. The vapor pressure of pure water at this temperature is 92.6 mmHg.What is the concentration of CaCl2 in mass percent?

The vapor above an aqueous solution contains 19.1 mg water per liter at 25 oC.Assuming ideal behavior, what is the concentration of the solute within the solution in mole percent?

A solution of 75.0 g of benzene (C6H6) and 75.0 g of toluene (C7H8) has a total vapor pressure of 80.9 mmHg at 303 K. Another solution of 100.0 g benzene and 50.0 g toluene has a total vapor pressure of 93.9 mmHg at this temperature.Find the vapor pressure of pure toluene at 303 K.

Two beakers are placed in a sealed box at 25 oC. One beaker contains 35.0 mL of a 5.5×10−2 M aqueous solution of a nonvolatile nonelectrolyte. The other beaker contains 35.0 mL of a 4.0×10−2 M aqueous solution of NaCl. The water vapor from the two solutions reaches equilibrium.In which beaker does the solution level rise, and in which one does it fall?

Two beakers are placed in a sealed box at 25 oC. One beaker contains 35.0 mL of a 5.5×10−2 M aqueous solution of a nonvolatile nonelectrolyte. The other beaker contains 35.0 mL of a 4.0×10−2 M aqueous solution of NaCl. The water vapor from the two solutions reaches equilibrium.What is the volume in the beaker with the aqueous solution of NaCl when equilibrium is attained, assuming ideal behavior?

Two beakers are placed in a sealed box at 25 oC. One beaker contains 35.0 mL of a 5.5×10−2 M aqueous solution of a nonvolatile nonelectrolyte. The other beaker contains 35.0 mL of a 4.0×10−2 M aqueous solution of NaCl. The water vapor from the two solutions reaches equilibrium.What is the volume in the beaker with the aqueous solution of a nonvolatile nonelectrolyte when equilibrium is attained, assuming ideal behavior?

Consider two solutions, one formed by adding 10 g of glucose (C6 H12 O6 ) to 1 L of water and the other formed by adding 10 g of sucrose (C12 H22 O11 ) to 1 L of water.Calculate the vapor
pressure for the first solution at 20 oC. (The vapor pressure of pure
water at this temperature is 17.5 torr.)

Consider two solutions, one formed by adding 10 g of glucose (C6 H12 O6 ) to 1 L of water and the other formed by adding 10 g of sucrose (C12 H22 O11 ) to 1 L of water.Calculate the vapor
pressure for the second solution at 20 oC. (The vapor pressure of pure
water at this temperature is 17.5 torr.)

A solution contains 4.08 g of chloroform (CHCl3 ) and 9.29 g of acetone (CH3 COCH3 ). The vapor pressures at 35 oC of pure chloroform and pure acetone are 295 torr and 332 torr, respectively.Assuming ideal behavior, calculate the vapor pressure of chloroform.

A solution contains 4.08 g of chloroform (CHCl3 ) and 9.29 g of acetone (CH3 COCH3 ). The vapor pressures at 35 oC of pure chloroform and pure acetone are 295 torr and 332 torr, respectively.The experimentally measured total vapor pressure of the solution at 35 oC was 312 torr. Is the solution ideal?

A solution contains 4.08 g of chloroform (CHCl3 ) and 9.29 g of acetone (CH3 COCH3 ). The vapor pressures at 35 oC of pure chloroform and pure acetone are 295 torr and 332 torr, respectively.Assuming ideal behavior, calculate the total vapor pressure above the solution.

A solution contains 0.111 mol
H2O and an unknown number of moles of sodium chloride. The vapor pressure of the solution at 30 oC is 25.7 torr. The vapor pressure of pure water at this temperature is 31.8 torr.Calculate the number of grams of sodium chloride in the solution. (Hint: Remember that sodium chloride is a strong electrolyte.)

The vapor pressure of carbon tetrachloride, CCl4, is 0.354 atm and the vapor pressure of chloroform, CHCl3, is 0.526 atm at 316 K. A solution is prepared from equal masses of these two compounds at this temperature.Calculate the mole fraction of the chloroform in the vapor above the solution.

The vapor pressure of carbon tetrachloride, CCl4, is 0.354 atm and the vapor pressure of chloroform, CHCl3, is 0.526 atm at 316 K. A solution is prepared from equal masses of these two compounds at this temperature.If the vapor above the original solution is condensed and isolated into a separate flask, what would the vapor pressure of chloroform be above this new solution?

The normal boiling point of ethanol, CH3CH2OH, is
78.4 C. When 8.65 g of a soluble nonelectrolyte is
dissolved in 100.0 g of ethanol at that temperature, the vapor pressure of the solution is 7.40 102 torr. What is the
molar mass of the solute?

Lysozyme is an enzyme that breaks bacterial cell walls. A solution containing 0.150 g of this enzyme in 210 mL of solution has an osmotic pressure of 0.953 torr at 25 oC.What is the molar mass of lysozyme?

A solution contains 11.05 g of unknown compound dissolved in 50.0 mL of water. (Assume a density of 1.00 g/mL for water.) The freezing point of the solution is -3.48 oC. The mass percent composition of the compound is 60.98% C, 11.94% H, and the rest is O.What is the molecular formula of the compound?

The osmotic pressure of a solution containing 2.10 g of an unknown compound dissolved in 175.0 mL of solution at 25 oC is 1.93 atm . The combustion of 24.02 g of the unknown compound produced 28.16 g
CO2 and 8.640 g
H2O.What is the molecular formula of the compound (which contains only carbon, hydrogen, and oxygen)?

A metal, M, of atomic weight 96 reacts with fluorine to form a salt that can be represented as MFx. In order to determine x and therefore the formula of the sal