Calculate the molar heat of fusion of this substance in kJ/mol. 300g of this unknown substance, with a molar mass of 180g/mol, gives off 65 kJ of energy as it freezes.

Question

Honors Chemistry; Molar Enthalpy of Fusion and Vaporization

Answer 1

You have 300 g of the material and since the molar mass is 180 g /mol you'll have

300 g / (180 g/mol) = 1.667 moles of the material

The material releases 65 kJ of energy when it freezes, so it will take 65 kJ to melt it. That's the enthalpy of fusion or molar heat of fusion (same property with two different names) 65 kJ/ 1.667 moles = 39 kJ/mol for the enthalpy of fusion or molar heat of fusion delta H fus