Chemistry | Chapter 10 Test Question

Question

A sample of liquid releases 60.5 kJ when it freezes. If the liquid has a molar heat of fusion of 2.642 kJ/mol, how many moles of the liquid were present?

Answer 1

When a liquid freezes, all of the heat energy released comes from the phase change, and there is no change in temperature. Thus, we have q = m∆Hf. In this case, we have 60.5 kJ = m(2.542 kJ/mol)

m = 60.5 kJ x 1 mol/2.542 kJ

m = 23.8 moles of liquid present