JEE Main 2025 Apr 4 Shift 2, Chemistry Q15: Factors Affecting The Rate of a Chemical Reaction

JEE Main2025Apr 4, Shift 2Chemistry

Consider the following plots of log of rate constant $k$ ( $lo g k$ ) vs $\frac{1}{T}$ for three different reactions. The correct order of activation energies of these reactions is

A
$E_{a_{2}} > E_{a_{1}} > E_{a_{3}}$
B
$E_{a_{1}} > E_{a_{3}} > E_{a_{2}}$
C
$E_{a_{1}} > E_{a_{2}} > E_{a_{3}}$
D
$E_{a_{3}} > E_{a_{2}} > E_{a_{1}}$

Solution

Take logarithm of the Arrhenius equation $k = A e^{- E_{a} / R T}$ :

$lo g k = lo g A - \frac{E _{a}}{2.303 R T}$

So a plot of $lo g k$ vs $1/ T$ is a straight line whose slope is $- \frac{E _{a}}{2.303 R}$ . The steeper (more negative) the slope, the larger the activation energy.

From the graph, the order of slope magnitudes is $(2) > (1) > (3)$ .

$∴$ $E_{a_{2}} > E_{a_{1}} > E_{a_{3}}$ .

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JEE Main 2025 Apr 4 Shift 2, Chemistry Q15: Factors Affecting The Rate of a Chemical Reaction

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