Ch.11 - Liquids, Solids & Intermolecular ForcesWorksheetSee 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 unknown liquid has a vapor pressure of 88 mmHg at 45 ◦C and 39 mmHg at 25◦C. What is its heat of vaporization?1. 32 kJ/mol 2. 2000 J/mol3. 32000 kJ/mol4. 2000 kJ/mol

Problem

An unknown liquid has a vapor pressure of 88 mmHg at 45 C and 39 mmHg at 25C. What is its heat of vaporization?

1. 32 kJ/mol 

2. 2000 J/mol

3. 32000 kJ/mol

4. 2000 kJ/mol

Solution

We’re being asked to determine the heat of vaporization of a substance. We’re given the vapor pressure at two different temperatures. For this problem, we can use the Clausius-Clapeyron Equation:



where:

P1 = vapor pressure at T1

P2 = vapor pressure at T2

ΔHvap = heat of vaporization (in J/mol)

R = gas constant (8.314 J/mol•K)

T1 and T2 = temperature (in K).


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