Question

You have two unknown liquids, A and B. The molar volumes of liquid A and vapor A at the standard boiling point are 149.9 cm3mol-1 and 35.71 Lmol-1respectively. Based on the experimental evidence presented below, estimate for liquid A dP/dT from the Clapeyron equation and estimate the percentage error if the Claussius-Clapeyron equation is used instead. Evidence: (a) A 0.500 molal solution of B in A raises the boiling point of pure A from 447.213K to 449.525K. (b) A solution of 17.79 g A in 250 g B lowers the freezing point of pure B from 278.701K to 277.279K. (c) The enthalpy of fusion for B is 45.070 kJmol-1 and the molar mass of B is 198.39gmol-1

Answer 1

Solution:

The clapeyron equation is,

Re-arranging the above equation we get,

by substituting the given datas in above equation we get, {for B, 1lt = 1000 cm^3}

dP/dT = (45.070 kJ/mol) / (277.279) K (35710 - 149.9) cm³mol^-1

         = 4.571E-6