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: An aqueous CaCl2 solution has a vapor pressure of 106.4 mmHg at 55.0 oC. The vapor pressure of pure water at this temperature is 118.0 mmHg. What is the concentration of CaCl2 in mass percent?A. 40.2%

Solution: An aqueous CaCl2 solution has a vapor pressure of 106.4 mmHg at 55.0 oC. The vapor pressure of pure water at this temperature is 118.0 mmHg. What is the concentration of CaCl2 in mass percent?A. 40.2%

Problem

An aqueous CaCl2 solution has a vapor pressure of 106.4 mmHg at 55.0 oC. The vapor pressure of pure water at this temperature is 118.0 mmHg. What is the concentration of CaCl2 in mass percent?

A. 40.2%
B. 25.3%
C. 18.3%
D. 15.3%
E. 21.2%

Solution

We’re being asked to determine the mass percent of CaCl2 in solution. Recall that the mass percent of a solution is given by:



We’re given the vapor pressure of the solution, 106.4 mmHg, and the vapor pressure of pure water, 118.0 mmHg. The vapor pressure of a solution can be given by Raoult’s Law:



where P˚ = vapor pressure of solvent and χ = mole fraction of solvent. This means that for this solution:



The mole fraction of H2O is:



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