JEE CHEMISTRY MCQ: CHEMICAL KINETICS

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Application +4 | -1

The energies of activation for forward and reverse reactions for

{A_2} + {B_2}\;\leftrightharpoons\;2AB

are

180\;kJ\;\mathrm{mo}{\mathrm{l}^{ - 1}}

and

200\;kJ\;\mathrm{mo}{\mathrm{l}^{ - 1}}

respectively. The presence of a catalyst lowers the activation energy of both (forward and reverse) reactions by

100\;kJ\;\mathrm{mo}{\mathrm{l}^{ - 1}}

. The enthalpy change of the reaction (

{A_2} + {B_2} \to 2AB

) in the presence of catalyst will be (in

kJ\;\mathrm{mo}{\mathrm{l}^{ - 1}}

)

View answer and explanation

Correct option: D

-20

Option D (-20) is correct because the enthalpy change is the difference between the activation energies of the forward and reverse reactions, and the catalyst lowers both by the same amount.

More Questions from CHEMICAL KINETICS

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The reaction

\mathrm{A}_2+\mathrm{B}_2 \rightarrow 2 \mathrm{AB}

follows the mechanism

\begin{aligned} & {{\text{A}}_2}\mathop \rightleftharpoons \limits_{{{\text{k}}_{ - 1}}}^{{{\text{k}}_1}} {\text{A}} + {\text{A (fast) }} \\ & \mathrm{A}+\mathrm{B}_2 \xrightarrow{\mathrm{k}_2} \mathrm{AB}+\mathrm{B} \text { (slow) } \\ & \mathrm{A}+\mathrm{B} \rightarrow \mathrm{AB} \text { (fast) } \end{aligned}

The overall order of the reaction is: For the first order reaction with the rate constant

k

, which expression gives the rate half-life period?

(Initial\mathrm{ }conc.\mathrm{ } = a)

Which of the following is a zero order reaction? For a certain reaction involving a single reactant, it is found that

C_0 \sqrt{T}

is constant, where

C_0

is the initial concentration of the reactant and

T

is the half-life. What is the order of the reaction? Arrhenius equation is The energy of activation for an uncatalysed reaction is

100 \mathrm{~kJ/mol}.

Presence of a catalyst lowers the energy of activation by

75 \%

. The

\log _{10} \frac{K_2}{K_1}

of the ratio of rate constant of catalysed and uncatalysed reactions at

27^{\circ} \mathrm{C}

is?

Assume the frequency factor is same for both reactions. (Given

2.303 \times 8.314=19.147

)