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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: At 35°C the vapor pressure of pure ethanol (C2H5OH, M = 46.1 g/mol) is pE° = 100.0 torr, and the vapor pressure of pure 1-propanol (C3H7OH, M = 60.1 g/mol) is pP° = 37.6 torr.  A solution at equilibri

Solution: At 35°C the vapor pressure of pure ethanol (C2H5OH, M = 46.1 g/mol) is pE° = 100.0 torr, and the vapor pressure of pure 1-propanol (C3H7OH, M = 60.1 g/mol) is pP° = 37.6 torr.  A solution at equilibri

Problem

At 35°C the vapor pressure of pure ethanol (C2H5OH, M = 46.1 g/mol) is pE° = 100.0 torr, and the vapor pressure of pure 1-propanol (C3H7OH, M = 60.1 g/mol) is pP° = 37.6 torr.  A solution at equilibrium at this temperature has a total pressure p = 84.2 torr.  Assuming the solution is ideal, what is the partial pressure of ethanol above the solution?

Solution

We’re being asked to determine the partial pressure of ethanol (C2H5OH) above a solution. Recall that the vapor pressure of a solution can be given by Raoult’s Law.


The given solutions are composed of ethanol and 1-propanol, 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 component. Recall that the mole fractions in a solution add up to 1. Since the solution is composed of ethanol and 1-propanol, this means:



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