Question

How much heat is required to raise the temperature of 230 g CH3OH(l) from 22.0 to 30.0 ∘C and then vaporize it at 30.0 ∘C? Use enthalpy of vaporization CH3OH(l) = 38.0 kJmol−1 and a molar heat capacity of CH3OH(l) of 81.1 Jmol−1K−1.

Answer 1

no of moles of CH3OH = 230/32 = 7.1875 moles

Heat =no of moles * heat capacity * temperature change

       = 7.1875*81.1*(30-20) = 5829.06Joules

Heat of vaporisation = no of moles* enthalpy of vaporisation

                             = 7.1875*38 = 273.125 kj = 273123 joules

Total heat = 5829.06Joules +273123 joules = 278954.06 joules >>>> answer