Question

A catalyst promoter __________the efficiency of a catalyst while a poison ________the efficiency of the catalyst.
A.Decreases, increases
B.Decreases, Decreases
C.Increases, increases
D.Increases, decreases

Answer 1

A catalyst is a substance that speeds up a chemical reaction, but is not consumed by the reaction. Hence, a catalyst can be recovered chemically unchanged at the end of the reaction it has been used to speed up.

Complete step by step answer:
A catalyst works by providing a different route, with lower activation energy ($\mathop E\nolimits_a$). Energy required to convert a reactant to product is known as activation energy.
Lesser the activation energy, faster is the reaction and vice-versa.
For chemicals to. React, their bonds must be rearranged because the bonds in the products are different from those in the reactants.
Positive catalysts increase the rate of reaction by lowering the activation energy whereas negative catalysts decrease the rate of reaction by increasing the activation energy.
A substance which increases the catalyst activity is known as catalyst promoter. Example: In harber’s cycle molybdenum or mixture of potassium and aluminium oxides act as promoters.
A substance which decreases the catalyst activity is known as catalyst poison. Example: The
Lindler’s catalyst used in the hydrogenation of alkyne to an alkene acts as a catalyst poison.
This option is not correct because it is the reverse of the correct answer.
Both the catalyst promoter and catalyst poison does not decrease the efficiency of the catalyst. Hence, this is not correct according to the question.
This option is also incorrect because both promoter and poison does not act in the same way on the catalyst.

So, the correct answer is Option D .

Note:
When a catalyst is used to increase the rate of reaction this phenomenon is known as catalysis. Autocatalytic reaction is one in which no specific catalyst is added. Instead, one of the products acts as a catalyst and increases the rate of formation of products.