Question:
The enthalpy of vapourisation of CCl4 is 30.5 kJ mol–1. Calculate the heat required for the vapourisation of 284 g of CCl4 at constant pressure. (Molar mass of CCl4 = 154 g mol–1).
Solution:
The enthalpy of vapourisation is given for 1 mole of CCl4 = 30.5 kJ mol–1
Hence, for 284 g, it will be = (mole no. × 30.5) kJ
Molar mass of CCl4 = 154 g mol–1 that means 154 g = 1 mole.
Therefore , 284 g = (284g/154gmol-1)= 1.84 mole.
Hence the heat required for the vapourisation of 284 g of CCl4 at constant pressure = (1.84 mol ×30.5 KJ mol-1) kJ
=56.12 KJ