MCQ
Given that the equilibrium constant for the reaction,

$2SO_{2(g)} + O_{2(g)} \rightleftharpoons 2SO_{3(g)}$ 

has a value of $278$ at a particular temperature. What is the value of the equilibrium constant for the following reaction at the same temperature?

$SO_{3(g)}  \rightleftharpoons SO_{2(g)} + \frac{1}{2} O_{2(g)}$

  • A
    $1.8 \times 10^{-3}$
  • B
    $3.6 \times 10^{-3}$
  • $6.0 \times 10^{-2}$
  • D
    $1.3 \times 10^{-5}$

Answer

Correct option: C.
$6.0 \times 10^{-2}$
c
$25O_{2(g)}+\mathrm{O}_{2(g)} \leftrightharpoons 25O_{3(g)}, \mathrm{K}=278$

By reversing the equation (i), we get

$25 \mathrm{O}_{3(\mathrm{g})} \leftrightharpoons 2 \mathrm{SO}_{2(\mathrm{g})}+\mathrm{O}_{2(\mathrm{g})}$

Equilibrium constant for this reaction is

$\mathrm{K}^{\prime}=1 / \mathrm{K}=1 / 278$

By dividing the equation (ii) by $2,$ we get desired equation.

$\mathrm{SO}_{3(\mathrm{g})} \leftrightharpoons \mathrm{SO}_{2(g)}+\frac 12 \mathrm{O}_{2(\mathrm{g})}$

Equilibrium constant for this reaction

$K^{\prime \prime}=\sqrt{K^{\prime}}=\sqrt{\frac{1}{K}}=\sqrt{\frac{1}{278}}$

$=0.0599 \approx 0.06$ 

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