Question

Mark the correct statement in a reversible reaction:
(A) A catalyst catalyses the forward reaction.
(B) A catalyst catalyses the backward reaction.
(C) A catalyst influences a direct and reverse reaction to the same extent.
(D) A catalyst increases the rate of forward reaction and decreases the rate of backward reaction.

Answer 1

Hint: A catalyst is a substance that takes part in a chemical reaction, and provides a suitable surface for reactant (catalytic action) resulting in the formation of an unstable intermediate easily. The most interesting part is that the catalyst, a reaction supporter itself, does not interfere in the formation of the product and is released along with the product as it is added to the reactant. Also, it helps to increase the yield of suitable major products and make the chemical reaction more energetic with its catalytic properties.

Complete Step by Step Answer:
A reversible reaction is a reaction that can be reversed or say can we obtain reactant from the product by removing the condition applied to the reactant to change it to the product. These reactions at any instant acquire an equilibrium state and further no exchange of energy takes place or the rate of formation of product is equal to the rate of formation of reactant.

A reactant changes to a product and a product changes to a reactant when the reactant and product observe energy greater than the activation energy (energy of transition state). Now, some reactions have large activation energy thus it becomes difficult to provide energy of such an amount, in that case, catalysts are used.

A catalyst is a substance that provides speed to the progress of reaction or can say lowering the activation energy \[\left( Ea \right)\] required by reactant and product to convert to product and reactant. So we need to provide less energy to reactants to convert to the product and vice versa.

Catalyst does not itself consume and release at the end of reaction but provides a suitable surface to reactant and accelerate the conversion of reactant to a product quickly and the process is known as catalysis. This means it increases the rate of formation of product (affect direct reaction rate) and reactant in a reversible reaction quickly (affect reverse reaction rate).
Thus, the correct option is D.

Note: It is important to note that catalyst not only increases the forward reaction rate but also the backward reaction rate equally so options A and B cannot be the suitable choice. Negative catalyst decreases the rate of forward and backward reaction. Also, the catalysts that increase the rate of biological reactions in our body are enzymes (homogeneous catalysis). Activation energy is the minimum amount of energy needs to provide to reactant so that it change to product or can say this is minimum energy which required to activate reactant to cause reaction.