COMEDK 2025 Afternoon Shift | Chemical Kinetics Question 6 | Chemistry

The hydrogenation of Ethyne is carried out at 600 K . The same reaction when carried out in presence of a catalyst maintaining the same rate constant, the temperature required is only 400 K . If the catalyst lowers the Activation energy of the reaction by $20 \mathrm{~kJ} / \mathrm{mol}$, what is the value of $\mathrm{E}_{\mathrm{a}}$ ?

$60 \mathrm{~kJ} / \mathrm{mol}$

$100 \mathrm{~kJ} / \mathrm{mol}$

$50 \mathrm{~kJ} / \mathrm{mol}$

$80 \mathrm{~kJ} / \mathrm{mol}$

COMEDK 2025 Afternoon Shift

MCQ (Single Correct Answer)

-0

The time needed for completion of $80 \%$ is $y$ times the half-life period of a first order reaction. What is the value of $y$ ?

0.648

3.46

2.32

0.322

COMEDK 2025 Afternoon Shift

MCQ (Single Correct Answer)

-0

Which one of the following is incorrect?

Rate constant equals the rate of reaction when concentration of reactants equals unity.

Larger the value of rate constant $(\mathrm{k})$ value faster is the chemical reaction.

The unit for rate constant for $n^{\text {th }}$ order reaction is $\left(\mathrm{mol} \mathrm{L}^{-1}\right)^{n-1} \mathrm{~s}^{-1}$

The value of rate constant $(\mathrm{k})$ is independent of concentration of reactants.

COMEDK 2025 Afternoon Shift

MCQ (Single Correct Answer)

-0

(i) and (ii) are 2 chemical reactions carried out at TK.

(i). $\mathrm{X} \rightarrow \mathrm{Y}+\mathrm{W}$ with $\mathrm{k}_1$ as rate constant.

(ii). $\mathrm{X} \rightarrow \mathrm{Z}+\mathrm{W}$ with $k_2$ as rate constant.

The Activation energy for reaction (ii) is 3 times that of reaction (i). What is the expression for $k_1$ ?

$k_1=-2 k_2 e^{2 E a_1 / R T}$

$k_1=k_2 e^{2 E a_1 / R T}$

$k_1=2 k_2 e^{E a_1 / R T}$

$k_1=k_2 / 2 e^{-E a_1 / R T}$

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