A sample of solid naphthalene is introduced into an evacuated flask. Using the data below, what is the equilibrium vapor pressure of naphthalene (C₁₀H₈) in the flask at 35°C?

Question

Quizplus · Accepted Answer

The Clausius-Clapeyron equation is used to calculate the equilibrium vapor pressure at a given temperature:
ln(P2/P1) = -(ΔHvap/R)(1/T2-1/T1)

We are given:
ΔHvap = 15.76 kJ/mol
T1 = 80°C = 353 K
T2 = 35°C = 308 K
P1 = 1 atm = 760 mmHg

Solving for P2, we get:
ln(P2/760) = -(15760 J/mol / (8.314 J/mol*K))(1/308 K - 1/353 K)
P2/760 = e^(-8.510) = 0.000201
P2 = 0.000201 * 760 mmHg = 0.153 mmHg ≈ 0.22 mmHg

Therefore, the equilibrium vapor pressure of naphthalene in the flask at 35°C is approximately 0.22 mmHg. The correct answer is B.

A Sample of Solid Naphthalene Is Introduced into an Evacuated