Chemistry Practice Problems Clausius-Clapeyron Equation Practice Problems Solution: An unknown liquid has a vapor pressure of 88 mmHg ...

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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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