Question

Solid HgO, liquid Hg, and gaseous O2 are placed in a glass bulb and the reaction below is allowed to reach equilibrium.
2HgO(s)
2Hg(l) + O2(g); ΔH = +181.6 kJ
With the system at equilibrium, the amount of Hg(l) in the bulb can be increased-
A) by removing some HgO(s). B) by adding an inert gas.
C) by adding some HgO(s). D) by increasing the pressure.
E) by increasing the temperature.

Answer 1

According to the Le-Charterlier's principle,

(1) If the temperature is raised, reaction will proceed in the direction in which some heat can destroy (absorbed) so that temperature of the system remains constant.

Thus increase in temperature shifts the equilibrium in the forward direction of those reactions which proceed with absorption of heat (endothermic reactions), and in the back ward direction of those reactions which proceed with the evolution of heat (exothermic reactions)

(2) If the pressure is increased, reaction will takes place in a direction which will bring about lowering f pressure. This implies that the equilibrium will shifts in the direction which produces the smaller no. of gas molecules.

(3)  If the concentration of reactants is increased or product is removed , the reaction will take place in the forward direction. If the concentration of reactants decreases or increasing the concentration of products the reaction will take place in the backward direction.

(4) Catalyst speeds up both forward & backward reactions to the same extent but does not have any effect on Equilibrium point.

(5)---> When the no. of moles of reactants & products are same the addition of inert gas has no effect

    ----> for a reaction at constant pressure ,addition of an inert gas will shifts the equilibrium in the direction in

            which there is increase in the no . of moles of the gases  

2HgO(s) 2Hg(l) + O2(g); ΔH = +181.6 kJ

With the system at equilibrium, the amount of Hg(l) in the bulb can be increased iff forward reaction takes place.

A) by removing some HgO(s) ----> backward reaction takes place

B) by adding an inert gas ----> both forward & backward reaction takes place with equal rate.
C) by adding some HgO(s) ----> forward reaction takes place

D) by increasing the pressure

Total number of moles of reactants = 2 moles

Total number of moles of products = 2+1 = 3 moles

On increasing Pressure it shifts towards lower volume side that means backward reaction takes place
E) Since the reaction is endothermic, by increasing the temperature forward reaction takes place.

Therefore the correct options are (C) & (E)