chemistry
posted by Andrew .
How much heat, in kilojoules, is evolved when a 3.70 kg sample of molten Cu freezes?
The normal boiling point is 1357 K, and heat of fusion is 13.05 KJ/mol.
2.) How much heat must be absorbed at 1357 K to melt a bar of copper (80 * 10 * 12 cm) assume d = 8.93 g/cm^3.

Andrew, I think I answered #1 earlier.
#2.
First calculate the volume of a bar of Cu that is 80 cm x 10 cm x 12 cm.
Volume = Length x width x depth. in cubic centimeters.
mass = density x volume. You have the density and you know the volume, you can calculate mass.
heat to melt = mass x heat of fusion.
Since the heat of fusion is listed in J/mole, you must change the mass of copper to moles from grams. moles = grams/molar mass.