Thermodynamics WS 3
Heats of ______
1.
What is the heat of fusion, in kJ/mol, of a substance if 48.3 g of the substance absorbs 8.714 kJ when it
melts? Assume that the molar mass of the substance is 27.1 g/mol. (A: 4.89 kJ/mol)
2.
How much energy will 5455 g of a substance release when it condenses? Assume that the heat of
vaporization of the substance is 16.0 kJ/mol and that its molar mass is 36.1 g/mol. (A: 2420 kJ)
3.
How many grams of a substance will release 4330 joules of energy on freezing? Assume that the heat
of fusion of the substance is 2.257 kJ/mol and that its molar mass is 115.4 g/mol. (A: 221 g)
from your textbook (p. 525, #82-85):
4.
How much heat is required to vaporize 343 g of liquid ethanol at its boiling point? Hvap = 38.6 kJ/mol
(A: 287 kJ)
5.
How much heat is evolved when 1255 g of water condenses to a liquid at 100oC? Hcond = -40.7 kJ/mol
(A: 2830 kJ)
6.
A sample of ammonia liberates 5.66 kJ of heat as it solidifies at its melting point. What is the mass of
the sample? Hsolid = -5.66 kJ/mol (A: -17.0 g)