Question

Calculate the total amount of energy (in kJ) necessary to raise the temperature of 2.00 L of ethanol (density = 0.7849 g/cm3) from 18 0C to its boiling point (78.3 0C) and then to fully vaporize the liquid. Assume that it is a closed system where no heat exchange with the surroundings take place.

(Given: Cethanol = 2.44 J/g·K; heat of vaporization of ethanol at 78.3 0C = 38.56 kJ/mol.)

Answer 1

The value of heat is $q=mC\Delta T$

$q=1569 ×2.44×(78.3-18)$

$q=230.967kJ$

Heat required to vaporize $=34.10 ×\Delta H _{vap}$ =1315.23kJ

Hence proved.