Question

In the dissociation reaction of $CaC{O_3}$ in a closed vessel, the forward reaction is favored by:
(A) Addition of more $CaC{O_3}$
(B) Removal of $CaO$
(C) Increasing the pressure.
(D) Decreasing the pressure by removing some $C{O_2}$ from the equilibrium mixture.

Answer 1

For dealing this question you must have some knowledge about the Le-Chatelier principle, which shows the movement of equilibrium whenever some changes are done. The changes may be the addition of reactants or products, it may happen when pressure increases or temperature decreases. So, you have to consider the balanced chemical equation for the above process and then try to figure out the options.

Complete step by step solution:
Now firstly, we have to write the equation for the above process. We have taken a closed vessel and then added calcium carbonate in it, an equilibrium is maintained having this reaction.
$CaC{O_3}(s)\, \rightleftharpoons \,CaO(s)\, + \,C{O_2}(g)$
Here you are seeing that calcium carbonate is a solid which dissociates and gives calcium oxide and releases carbon dioxide now if changes are made. So, according to Le-Chatelier principle always change gets balanced to nullify the effect, it means if we are increasing pressure then the equilibrium gets disturbed to balance it or to nullify the change the equilibrium moves towards that direction where the change gets cancelled.
Let’s take the first option and see whether by this the equilibrium will move forward or not. So, addition of calcium carbonate ( $CaC{O_3}$ ) will increase the concentration of the reactant and thus nullify the change equilibrium. In the second option we have removal of calcium oxide, so if we remove calcium oxide from the vessel equilibrium will move in that side where the concentration of calcium oxide will increase it means it also moves in forward direction.
For the third option which is the increase of pressure, so increase is pressure will move the equilibrium in the opposite direction that is where the pressure is less so the equilibrium will move in backward direction. This is not our answer. Last option is the decrease in pressure by removal of carbon dioxide, for this decrease in pressure equilibrium will shift automatically in that direction where pressure will increase. As you are seeing carbon dioxide gas in the right hand side of reaction that is in forward reaction, thus equilibrium will move in forward reaction.
Correct options are A, B and D.

Note :
Favored forward reaction means that we want a larger amount, so there are some changes that should be down to move the equilibrium. For this reaction, if we want to need the product in larger amounts during equilibrium, we should increase the concentration of calcium carbonate, decrease the concentration of calcium oxide and decrease the pressure by all these phenomena we are moving equilibrium in forward direction.