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Ch.13 - Solutions
Chapter 13, Problem 75

A solution contains 4.08 g of chloroform (CHCl3) and 9.29 g of acetone (CH3COCH3). The vapor pressures at 35 °C of pure chloroform and pure acetone are 295 torr and 332 torr, respectively. Assuming ideal behavior, calculate the vapor pressures of each of the components and the total vapor pressure above the solution. The experimentally measured total vapor pressure of the solution at 35 °C is 312 torr. Is the solution ideal? If not, what can you say about the relative strength of chloroform–acetone interactions compared to the acetone–acetone and chloroform–chloroform interactions?

Verified step by step guidance
1
Calculate the mole fraction of chloroform (CHCl_3) in the solution. Use the formula: \( \text{mole fraction of CHCl}_3 = \frac{\text{moles of CHCl}_3}{\text{moles of CHCl}_3 + \text{moles of CH}_3\text{COCH}_3} \).
Calculate the mole fraction of acetone (CH_3COCH_3) in the solution. Use the formula: \( \text{mole fraction of CH}_3\text{COCH}_3 = \frac{\text{moles of CH}_3\text{COCH}_3}{\text{moles of CHCl}_3 + \text{moles of CH}_3\text{COCH}_3} \).
Use Raoult's Law to calculate the partial vapor pressure of chloroform: \( P_{\text{CHCl}_3} = \text{mole fraction of CHCl}_3 \times P^0_{\text{CHCl}_3} \), where \( P^0_{\text{CHCl}_3} \) is the vapor pressure of pure chloroform.
Use Raoult's Law to calculate the partial vapor pressure of acetone: \( P_{\text{CH}_3\text{COCH}_3} = \text{mole fraction of CH}_3\text{COCH}_3 \times P^0_{\text{CH}_3\text{COCH}_3} \), where \( P^0_{\text{CH}_3\text{COCH}_3} \) is the vapor pressure of pure acetone.
Calculate the total vapor pressure of the solution by adding the partial pressures: \( P_{\text{total}} = P_{\text{CHCl}_3} + P_{\text{CH}_3\text{COCH}_3} \). Compare this with the experimentally measured total vapor pressure to determine if the solution is ideal. If the calculated pressure is different from the experimental value, discuss the relative strength of interactions.
Related Practice
Open Question
A solution contains naphthalene (C10H8) dissolved in hexane (C6H14) at a concentration of 12.35% naphthalene by mass. Calculate the vapor pressure of hexane above the solution at 25 °C. The vapor pressure of pure hexane at 25 °C is 151 torr.
Textbook Question

A solution contains 50.0 g of heptane (C7H16) and 50.0 g of octane (C8H18) at 25 °C. The vapor pressures of pure heptane and pure octane at 25 °C are 45.8 torr and 10.9 torr, respectively. Assuming ideal behavior, answer the following: d. Why is the composition of the vapor different from the composition of the solution?

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Textbook Question

A solution contains a mixture of pentane and hexane at room temperature. The solution has a vapor pressure of 258 torr. Pure pentane and hexane have vapor pressures of 425 torr and 151 torr, respectively, at room temperature. What is the mole fraction composition of the mixture? (Assume ideal behavior.)

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Open Question
A solution of methanol and water has a mole fraction of water of 0.312 and a total vapor pressure of 211 torr at 39.9 °C. The vapor pressures of pure methanol and pure water at this temperature are 256 torr and 55.3 torr, respectively. Is the solution ideal? If not, what can be inferred about the relative strengths of the solute–solvent interactions compared to the solute–solute and solvent–solvent interactions?
Textbook Question

A glucose solution contains 55.8 g of glucose (C6H12O6) in 455 g of water. Determine the freezing point and boiling point of the solution.

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Open Question
An ethylene glycol solution contains 21.2 g of ethylene glycol (C2H6O2) in 85.4 mL of water. Determine the freezing point and boiling point of the solution. (Assume a density of 1.00 g/mL for water.)