Question

H2O has a mc021-1.jpgHvap = 40.7 kJ/mol. What is the quantity of heat that is released when 27.9 g of H2O condenses?

Answer 1

The molecular weight of H2O is 18g/mol.
Therefore, 27.9 g H2O / (1mol/18g) = 0.155 mol H2O
Calculating only for the latent heat, the heat required to be released for this amount of H2O to condense is:
40.7 kJ/mol (0.155 mol) = 6.3 kJ or -6.3 kJ since it is to be released