A certain substance has a heat of vaporization of 66.27 kJ/mol. At what Kelvin temperature will the vapor pressure be 6.50 times higher than it was at 341 K?

Answer 1

We know the clausius clapeyron equation looks at the relationship between pressure, temperature and the heat of vaporization.

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

we are told delta Hvap = 66.27 kJ/mol=66270 J/mol, T2=?, T1 = 341 K and we know this relationship for P:

P2=6.5*P1

So when we plug in:

ln(P1/6.5 P1) = 66270 /8.314 (1/T2 - 1/341)

The P1 would cancel so:

ln(1/6.5) = 66270 /8.314 (1/T2 - 1/341)

and when we solve for T2: 370.7 K

**we must plug in Hvap as J/mol because R is 8.314 J/molK and our units must cancel!