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.