Enthalpy of Vaporization Calculation for Chloroform

What is the enthalpy of vaporization (ΔHvap) of chloroform?

The vapor pressure of liquid chloroform, CHCl3, is 400.0 torr at 24.1°C and 100.0 torr at -6.3°C. What is ΔHvap of chloroform?

a) 20.0 kJ/mol
b) 40.0 kJ/mol
c) 60.0 kJ/mol
d) 80.0 kJ/mol

Answer:

The ΔHvap of chloroform is found to be approximately 20.0 kJ/mol. Option A is the correct answer.

The enthalpy of vaporization (ΔHvap) of chloroform can be calculated using the Clausius-Clapeyron equation. By using the given vapor pressure values of chloroform at two different temperatures, we can calculate ΔHvap.

Substituting the given values into the Clausius-Clapeyron equation:

ΔHvap = -R * ln(P2/P1) / (1/T2 - 1/T1)

Given values: R = 8.314 J/mol·K, P1 = 400.0 torr, P2 = 100.0 torr, T1 = 24.1°C = 297.25 K, and T2 = -6.3°C = 266.85 K

Calculating the value of ΔHvap:

ΔHvap = -8.314 * ln(100.0/400.0) / (1/266.85 - 1/297.25)

ΔHvap ≈ 20.0 kJ/mol

Therefore, the enthalpy of vaporization (ΔHvap) of chloroform is approximately 20.0 kJ/mol, which corresponds to option a) 20.0 kJ/mol.