please help me with chemistry and heat

Question

What is the heat required to vaporize 54.3 g of liquid ammonia, NH₃, at its boiling point? The ΔH° of vaporization of ammonia is 23.4 kJ/mol. Use a molar mass with at least as many significant figures as the data given.

 Answer in kJ

Answer 1

molar mass NH3 = 17.0 g/mol

moles NH3 present = 54.3 g NH3 x 1 mol/17 g = 3.19 moles

heat to vaporize 3.19 moles = 23.4 kJ/mol x 3.19 moles = 74.7 kJ (3 sig. figs.)