Question

According to the Arrhenius equation:
A.High activation energy usually implies a fast reaction.
B.Rate constant increases with increase in temperature. This is due to a greater number of collisions whose energy exceeds the activation energy.
C.Higher the magnitude of activation energy, stronger is the temperature dependence of the rate constant
D.The pre-exponential factor is a measure of the rate at which collisions occur, irrespective of their energy.

Answer 1

Hint: The equation called the Arrhenius equation is usually written as ${\text{k = A}}{{\text{e}}^{\dfrac{{{\text{ - }}{{\text{E}}_{\text{a}}}}}{{{\text{RT}}}}}}$ where the pre-exponential factor ${\text{A}}$ is a constant and is called frequency factor and ${{\text{E}}_{\text{a}}}$ is called the activation energy, R is the gas constant and T is the temperature. The activation energy calculated by the formula are rate constants at different temperatures.

Complete step by step answer:
Now according to Arrhenius equation: ${\text{k = A}}{{\text{e}}^{\dfrac{{{\text{ - }}{{\text{E}}_{\text{a}}}}}{{{\text{RT}}}}}}$
When ${{\text{E}}_{\text{a}}}$ increases, the value of \[{{\text{e}}^{\dfrac{{{\text{ - }}{{\text{E}}_{\text{a}}}}}{{{\text{RT}}}}}}\] decreases due to the negative sign. This implies that higher activation means a lower rate of reaction. Thus, option A can be eliminated.
When ${\text{T}} \to \infty $ then \[{{\text{e}}^{\dfrac{{{\text{ - }}{{\text{E}}_{\text{a}}}}}{{{\text{RT}}}}}} \to 0\] which means that, ${\text{k}} \to {\text{A}}$ , then we can see that when the temperature increase, the rate constant increases and approaches the value close to Arrhenius constant. So, option B is correct.
As we know that with higher activation energy, the rate of reaction decreases and with higher temperature, the rate of reaction increases. So, at higher activation energies, i.e. if the activation energy is constant, the rate of reaction is dependent only on the temperature. So, option C is correct.
The pre-exponential factor is always constant for a particular reaction, irrespective of temperature. It represents the frequency of collision at a standard concentration. Thus, option D is correct.

Hence, option B, C and D are correct.

Note:
Arrhenius equation is employed to calculate the rate of a reaction. It is an important part of chemical kinetics. It helps in understanding the effect of temperature on the rate of a reaction. This equation was proposed in 1889 by Svante Arrhenius.