The equation for the rate constant is given as:
$k = Ae^{(-Ea/RT)}$
In this equation, the rate constant (k) represents the speed at which a reaction occurs. To analyze the effect of certain changes on the reaction rate, we need to understand how each factor affects the rate constant.
(a) Decreasing the rate constant (k) would actually slow down the reaction, as it represents the speed of the reaction. Therefore, a decrease in k would not lead to a more rapid reaction. Thus, option (1) is incorrect.
(b) Decreasing the pre-exponential factor (A) would also result in a decrease in the rate constant. A smaller value of A would indicate a lower probability for successful collisions or fewer available reactant molecules, both of which would slow down the reaction. Therefore, a decrease in A would not lead to a more rapid reaction. Hence, option (2) is also incorrect.
(c) The activation energy (Ea) is a barrier that reactant molecules must overcome for a reaction to occur. Increasing the activation energy would make it more difficult for the reactants to reach the transition state and proceed with the reaction. Conversely, decreasing the activation energy would lower the barrier, making it easier for the reaction to occur. Therefore, a decrease in the activation energy (Ea) would lead to a more rapid reaction. Thus, option (3) is correct.
(4) The temperature (T) is present in the denominator of the Arrhenius equation. Increasing the temperature leads to a higher value in the exponential term, resulting in a larger rate constant and a faster reaction. Therefore, a decrease in temperature would not lead to a more rapid reaction. Hence, option (4) is incorrect.
In summary, the correct answer is (3) Ε (activation energy). |
