At 1 atm pressure the heat of sublimation of gallium is 277 kJ/mol and the heat of vaporization is 271 kJ/mol.How much heat is required to melt 0.500 mol of gallium at 1.00 atm pressure?

Question

Quizplus · Accepted Answer

Since we are melting Gallium, we need to use the heat of fusion equation Q = nΔHf. However, the heat of fusion is not given in the question, so we need to use the fact that the heat of sublimation and vaporization are equal at the triple point. This means that we can write the following two equations:

ΔHsub + ΔHvap = ΔHfus

277 kJ/mol + 271 kJ/mol = ΔHfus

ΔHfus = 548 kJ/mol

Now we can use the equation Q = nΔHf to solve for Q:

Q = (0.500 mol)(548 kJ/mol)

Q = 274 kJ

However, this answer is for the heat required to freeze Gallium, not melt it. To get the heat required to melt Gallium, we simply need to invert the sign:

Q = -274 kJ

So the amount of heat required to melt 0.500 mol of Gallium at 1.00 atm pressure is 3.00 kJ.

At 1 Atm Pressure the Heat of Sublimation of Gallium