A substance has a heat of fusion of 61.5 kj/mol and a heat of deposition of 167.4 kj/mol. What is 175 heat of sublimation in kj/mol?
A) 61.5-167.4
B) 61.5+ 167.4
C) -61.5
D) 167.4
E) 167.4-61.5
To find the heat of sublimation, we need to understand what sublimation is. Sublimation refers to the process of a substance transitioning from the solid phase directly to the gas phase, without passing through the liquid phase.
We are given the heat of fusion, which is the energy required to change a substance from solid to liquid at its melting point. In this case, the heat of fusion is 61.5 kJ/mol. However, sublimation does not involve a change in phase from solid to liquid, so the heat of fusion is not directly applicable.
Instead, we should consider the heat of deposition, which is the energy released when a substance transitions from gas to solid. The given heat of deposition is 167.4 kJ/mol.
To find the heat of sublimation, we need to combine the heat of fusion and the heat of deposition. Since sublimation involves both the solid-to-gas and gas-to-solid transitions, we add these two values.
Heat of Sublimation = Heat of Fusion + Heat of Deposition
Heat of Sublimation = 61.5 kJ/mol + 167.4 kJ/mol
Calculating this sum, we get:
Heat of Sublimation = 228.9 kJ/mol
Therefore, the correct answer is:
E) 167.4 - 61.5