A sample 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 dа ta:

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