MCQ
The value of equilibrium constant of the reaction

$HI \rightleftharpoons \frac {1}{2} H_{2(g)} + \frac{1}{2} I_{2(g)}$

is $8.0$. The equilibrium constant of the reaction

$H_{2( g )} + I_{2(g)} \rightleftharpoons   2HI_{ ( g )}$ will be

  • A
    $16$
  • B
    $1/8$
  • C
    $1/16$
  • $1/64$

Answer

Correct option: D.
$1/64$
d
$\mathrm{HI}(\mathrm{g}) \rightleftharpoons \mathrm{H}_{2} / 2(\mathrm{g})+\mathrm{I}_{2} / 2(\mathrm{g})$

$\mathrm{K}_{1}=\frac{\left[\mathrm{H}_{2}\right]^{1 / 2}\left[\mathrm{I}_{2}\right]^{1 / 2}}{[\mathrm{HI}]}$

$\mathrm{H}_{2}(\mathrm{g})+\mathrm{I}_{2}(\mathrm{g}) 2 \mathrm{H}(\mathrm{g})$

$\mathrm{K}_{2}=\frac{[\mathrm{H}]^{2}}{\left[\mathrm{H}_{2}\right]\left[\mathrm{I}_{2}\right]}$

From eqs $(i)$ and $(ii)$ $\mathrm{K}_{1}^{2}=\frac{1}{\mathrm{K}_{2}}$

$\mathrm{K}_{1}=8.0$

$\mathrm{k}_{2}=\frac{1}{\mathrm{k}_{1}^{2}}=\frac{1}{8^{2}}=\frac{1}{64}$

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