The molar enthalpy of vaporization of hexane (C₆H₁₄)is 28.9 kJ/mol, and its normal boiling point is 68.73°C.What is the vapor pressure of hexane at 25°C? A)4.44 torr B)117 torr C)171 torr D)759 torr E)3370 torr

Question

Quizplus · Accepted Answer

The Clausius-Clapeyron equation relates vapor pressure with temperature and enthalpy of vaporization:

ln(P2/P1) = (-ΔHvap/R)(1/T2 - 1/T1)

Where P1 and T1 are the known values at the normal boiling point and P2 is the vapor pressure at the unknown temperature of 25°C (298 K).

R is the gas constant (8.314 J/mol·K) and ΔHvap is given as 28.9 kJ/mol.

Plugging in the values:

ln(P2/1 atm) = (-28.9 kJ/mol / (8.314 J/mol·K)) * (1/298 K - 1/341.88 K)

ln(P2/1 atm) = -4.83

P2 = 171 torr (rounded to 3 significant figures)

The Molar Enthalpy of Vaporization of Hexane (C6H14)is 28

The Molar Enthalpy of Vaporization of Hexane (C₆H₁₄)is 28