1) how much heat energy is required to boil 20.8 g of ammonia, NH3? The molar heat of vaporization of ammonia is 23.4 kJ/mol.

2) How much heat energy is required to melt 931.0 g pf HBr? The molar heat of fusion of HBr is 2.41 kj/mol

3) how many grams of benzene C6H6 can be melted with 75.4 kj of heat energy? the molar heat of fusion of benzene is 9.95 Kj/mol