Question

The melting point of the ice is
(A) increases with increase in pressure
(B) decreases with increasing the pressure
(C) Is independent of pressure
(D) is proportional to the pressure

Answer 1

Hint
Here we use the second law of thermodynamics and Lechatelier’s principle. Entropy plays an important role in changes occurring in the system. A system always wants to be in equilibrium.

Complete step by step answer
The answer could be explained by using LeChatelier’s principle which states that when the system is in equilibrium, any external changes that try to take it out of equilibrium for example applying pressure on ice will cause the system to adjust in a way to counteract this change.
A system wants to be in equilibrium. A state of equilibrium means a system has achieved maximum entropy. This is why when we change any external factors such as pressure the system undergoes change in order to maintain its equilibrium and this is the reason that the transition temperature of the system changes with external factors like pressure. For most of the systems, the melting point increases with increase in pressure except for water. This strange behavior of the water ice system is observed because water expands when it freezes i.e. ice occupies more volume than liquid water. So, when the external pressure increases the ice water system maintains its entropy by occupying the smaller volume and since water occupies less volume, more and more ice is converted into water resulting in a decrease in the melting point. Hence, we can say that the melting point of ice increases with decrease in pressure.
Thus, option (B) is correct.

Note
It must be remembered that the transition temperature depends upon the external changes of the system. Ice is an exceptional case in which melting point decreases with increases in pressure. This happens because the system wants to attain the state of equilibrium.