Question

A catalyst remains unchanged at the end of the reaction regarding
A. Mass
B. Physical state
C. Physical state and chemical composition
D. Mass and chemical composition

Answer 1

Hint: Catalyst comes from the combination of two Greek words kata (meaning wholly) and lein (meaning to loosen). It is a chemical substance that increases the speed of a reaction and does not get consumed in the process. This process is called catalysis.

Complete Step by Step Answer:
- The pace of a reaction usually increases after the addition of a catalyst.
- It stays as it is in terms of the chemical composition and mass at the end of the reaction.
- There is no dissimilarity in terms of the chemical structure or amount of catalyst at the initial or final stage of the reaction.
- It does not get consumed during the reaction.
- It reduces the activation energy of the reactants. It decreases the energy barrier and thus makes the reaction faster.
- Its physical state such as size, colour, etc., may change.
- For example, manganese dioxide is used as a catalyst in the decomposition of potassium chlorate and changes its physical state from coarse powder to fine powder at the end of the reaction.
- Smooth platinum gauze is used for the oxidation of ammonia and may become rough at the end of the reaction.
So, D is correct.
So, option D is correct.

Note: It must be noted that catalysts only accelerate the rate of reaction, stay the same after the reaction, and have specific activity. It does not get consumed during the reaction.