Question

For an equilibrium \[{{\text{H}}_2}{\text{O}}\left( s \right) \rightleftharpoons {{\text{H}}_2}{\text{O}}\left( l \right)\], which of the following statement is true?
A) The pressure changes do not affect the equilibrium
B) More of ice melts if pressure on the system is increased
C) More of liquid freezes if pressure on the system is increase
D) The pressure changes may increase or decrease the degree of advancement of the reaction depending upon the temperature of the system.

Answer 1

Hint:Applying Le chatelier’s principle, When we increase the system pressure, there will be a decrease in the volume of the system. This is in order to nullify the effect of increase in pressure and regain the equilibrium state.

 Complete step by step answer:
The equilibrium \[{{\text{H}}_2}{\text{O}}\left( s \right) \rightleftharpoons {{\text{H}}_2}{\text{O}}\left( l \right)\] represents the melting of ice to form liquid water.
Ice has more volume than liquid water. There is a decrease in volume during melting of ice.
In other words, you can say that during melting, the volume change is negative.
So, when you increase the pressure, the system will try to decrease the pressure by shifting the equilibrium in a direction, where there is decrease in the volume. Thus, when you increase the pressure, the system will decrease the volume.
When you increase the pressure, the equilibrium \[{{\text{H}}_2}{\text{O}}\left( s \right) \rightleftharpoons {{\text{H}}_2}{\text{O}}\left( l \right)\] will shift to right.
 Due to this, more and more ice will melt to form liquid water. Ice having higher volume is replaced with liquid water having lesser volume. This leads to decrease in the system volume and minimizes the effect of increase in pressure.
More of ice melts if you increase the pressure on the system.
More of ice forms from liquid water if you decrease the pressure on the system.
So,Option “B” is correct.

Note:Ice melts at a temperature of \[0{{\text{ }}^o}{\text{C}}\] or \[273{\text{ K}}\] at pressure of \[1{\text{ atm}}\] . This temperature is the melting point of ice. When you continuously heat the ice, its temperature will keep on increasing till it reaches \[0{{\text{ }}^o}{\text{C}}\] . At this temperature, ice will melt. All the heat that is being supplied is used to melt the ice. During this period, the temperature remains constant. When you further supply the heat, the temperature will increase again.