Question:

At \(1\,\mathrm{K}\), \(15\) moles of \(\mathrm{H_2}\) reacts with \(5.2\) moles of \(\mathrm{I_2}\) and forms \(10\) moles of \(\mathrm{HI}\). The equilibrium constant for the reaction \[ 2\mathrm{HI}(g)\rightleftharpoons \mathrm{H_2}(g)+\mathrm{I_2}(g) \] is

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Use an ICE (Initial--Change--Equilibrium) table for equilibrium problems. If all species are in the same volume, moles may be used directly in the equilibrium expression because the volume terms cancel.
Updated On: Jul 9, 2026
  • \(50\)
  • \(100\)
  • \(2\times10^{-2}\)
  • \(1\times10^{-2}\) \bigskip
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The Correct Option is C

Solution and Explanation

Concept: For the reaction \[ 2\mathrm{HI}\rightleftharpoons \mathrm{H_2}+\mathrm{I_2}, \] the equilibrium constant is \[ K_c=\frac{[\mathrm{H_2}][\mathrm{I_2}]}{[\mathrm{HI}]^2}. \]

Step 1:
Determine equilibrium moles. Initially, \[ \mathrm{H_2}=15,\qquad \mathrm{I_2}=5.2,\qquad \mathrm{HI}=0 \] Since \(10\) moles of HI are formed, \[ \mathrm{H_2+I_2\rightarrow 2HI} \] Therefore, \[ x=\frac{10}{2}=5 \] Equilibrium moles: \[ \mathrm{H_2}=15-5=10 \] \[ \mathrm{I_2}=5.2-5=0.2 \] \[ \mathrm{HI}=10 \]

Step 2:
Calculate \(K_c\). \[ K_c=\frac{10\times0.2}{10^2} =\frac{2}{100} =2\times10^{-2} \]

Step 3:
Final conclusion. \[ \boxed{K_c=2\times10^{-2}} \] Hence, the correct option is \(\boxed{(C)}\).
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