MCQ
For a given exothermic reaction, $K_p$ and $K'_p$  are the equilibrium constants at temperatures $T_1$ and $T_2,$ respectively. Assuming that heat of reaction is constant in temperature range between $T_1$ and $T_2,$ it is readily observed that
  • $K_p > K'_p$
  • B
    $K_p < K'_p$
  • C
    $K_p = K'_p$
  • D
    $K_p = \frac{1}{K'_p}$

Answer

Correct option: A.
$K_p > K'_p$
a
$\log \frac{K_{p}^{\prime}}{K_{p}}=-\frac{\Delta H}{2.303 R}\left[\frac{1}{T_{2}}-\frac{1}{T_{1}}\right]$

For exothermic reaction, $\Delta \mathrm{H}= -ve$ i.e. heat is evolved. The temperature $\mathrm{T}_{2}$ is higher than $\mathrm{T}_{1}$

Thus, $\left(\frac{1}{T_{2}}-\frac{1}{T_{1}}\right)$ is negative.

so, $\log K_{p}^{\prime}-\log K_{p}=-$ ve or $\log K_{p}>\log K_{p}^{\prime}$

$ K_{p}>K_{p}$

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