How much energy (in kilojoules) is released when 12.3g of steam at 121.5 degree C is condensed to give liquid water at 64.5 degree C? The heat of vaporization of liquid water is 40.67kj/mol , and the molar heat capacity is 75.3 J/(K mol) for the liquid and 33.6 J/(K mol)for the vapor.

Answer 1

I do these problems in steps.
q1 = move steam at 121.5 C to steam at 100.
q1 = mass x specific heat x delta T.

q2 = condense steam at 100 to liquid at 100.
q2 = mass x heat vaporization.

q3 = move liquid water at 100 to liquid water at 64.5 C.
q3 = mass x specific heat x delta T.

The total energy is q1 + q2 + q3.