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

Solution: 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

Solution: 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

Problem

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 benzene 303 K.

Solution

We’re being asked to determine the vapor pressure of pure benzene at 303 K. Recall that the vapor pressure of a solution can be given by Raoult’s Law.


The given solutions are composed of benzene and toluene, which are both volatile. For a solution with volatile solute and solvent, Raoult’s Law is given as:




where P˚ = vapor pressure of pure component and χ = mole fraction of componentMole fraction is given by:



where i = van’t Hoff factor. We first need to determine the mole fraction of the solute and solvent for each solution. The molar mass of benzene, C6H6­, is:

6 × 12.01 g/mol C = 72.06 g/mol C

6 × 1.01 g/mol H = 6.06 g/mol H

Molar Mass = 78.12 g/1 mol C6H6


The molar mass of toluene, C7H8­, is:

7 × 12.01 g/mol C = 84.07 g/mol C

8 × 1.01 g/mol H = 8.08 g/mol H

Molar Mass = 92.15 g/1 mol C7H8


View the complete written solution...