Asample of benzene was vaporized at 25◦c. when 37.5 kj of heat was supplied, 95.0 g of the liquid benzene vaporized. what is the enthalpy of vaporization of benzene at 25◦c?
1. 30.8 kj/mol
2. 13.4 kj/mol
3. 43.0 kj/mol
4. 6.09 kj/mol
5. 25.6 kj/mol

Enthalpy of vaporization = 30.8 kj/mol

Explanation:

Given data:

Mass of benzene = 95.0 g

Heat evolved = 37.5 KJ

Enthalpy of vaporization = ?

Solution:

Molar mass of benzene = 78 g/mol

Number of moles = mass/ molar mass

Number of moles = 95 g/ 78 g/mol

Number of moles = 1.218 mol

Enthalpy of vaporization =  37.5 KJ/1.218 mol

Enthalpy of vaporization = 30.8 kj/mol