Question

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 DeltaH of vaporization for chloroform?

Answer 1

ΔH vaporization of chloroform is 30.1kJ/mol

Step-by-step explanation:

It is possible to find ΔH of vaporization of certain compound knowing vapor pressure under 2 different absolute temperatures (In Kelvin) by using Clausius-Clapeyron equation:

`ln(P_2)/(P_1)=(DeltaHvap)/(R) ((1)/(T_1) - (1)/(T_2) )`

Where P is vapor pressure. R is gas constant (8.314J/molK) and T absolute temperature of 1, first state and 2, final state.

Absolute temperatures in the problem are:

T₁ = 24.1°C + 273.15 = 297.25K

T₂ = -6.3°C + 273.15 = 266.85K

Replacing:

`ln(P_2)/(P_1)=(DeltaHvap)/(R) ((1)/(T_1) - (1)/(T_2) )`

`ln(100torr)/(400.0torr)=(DeltaHvap)/(8.314J/molK) ((1)/(297.25K) - (1)/(266.85K) )`

`ln(100torr)/(400.0torr)={DeltaHvap}* -4.6x10^(-5)mol/J`

30073J/mol = 30.1kJ/mol = ΔHVap

ΔH vaporization of chloroform is 30.1kJ/mol