Question

A catalysed reaction mechanism has an activation energy and thus, causes a reaction rate.
A.Higher, lower
B.Higher, higher
C.Lower, higher
D.Lower, steady
E.Higher, steady

Answer 1

The activation energy of a chemical reaction is very closely related to its reaction rate. The activation energy determines the value of the rate constant at a given temperature and thus the overall reaction rate. Catalysts are defined as substances that participate in a chemical reaction but they are not changed or consumed. The activation energy is defined as the minimum energy that is needed for a reaction to take place.

Complete step by step answer:
The magnitude of the activation energy $({E_a})$ determines the value of the rate constant (k) at a given temperature and thus the overall reaction rate. Catalysts provide a means of reducing activation energy $({E_a})$ and increase the reaction rate. Catalysts are defined as substances that participate in a chemical reaction but they are not changed or consumed but they provide a new mechanism for a reaction to occur which has a lower activation energy than that of the reaction without the catalyst.
A catalysed reaction mechanism has a lower activation energy and thus it causes a higher reaction rate. A catalyst provides an alternate pathway having lower activation energy $({E_a})$.

Therefore, the correct answer is option (C).

Note: The catalysts function by providing an alternate reaction mechanism that has a lower activation energy than would be found in the absence of the catalyst. A catalyst decreases the activation energy for both the forward as well as the reverse reactions and hence they accelerate both the forward and the reverse reactions. Consequently, the presence of a catalyst permits a system to reach equilibrium more quickly, but it does not affect on the position of the equilibrium as reflected in the value of its equilibrium constant.