JEE Main · 2019 · Shift-IImediumCEQ-048

For the following reactions, equilibrium constants are given: S(s) + O2(g) SO2(g);\ K1 = 1052 2S(s) + 3O2(g) 2SO3(g);\…

Chemical Equilibrium · Class 11 · JEE Main Previous Year Question

Question

For the following reactions, equilibrium constants are given: S(s)+O2(g)SO2(g); K1=1052\mathrm{S(s) + O_2(g) \rightleftharpoons SO_2(g)};\ K_1 = 10^{52} 2S(s)+3O2(g)2SO3(g); K2=10129\mathrm{2S(s) + 3O_2(g) \rightleftharpoons 2SO_3(g)};\ K_2 = 10^{129} The equilibrium constant for the reaction 2SO2(g)+O2(g)2SO3(g)\mathrm{2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)} is:

Options
  1. a

    1015410^{154}

  2. b

    102510^{25}

  3. c

    1018110^{181}

  4. d

    107710^{77}

Correct Answerb

102510^{25}

Detailed Solution

Step 1 — Target reaction: 2SO2+O22SO3\mathrm{2SO_2 + O_2 \rightleftharpoons 2SO_3}

Step 2 — Construct from given reactions:

  • Reverse reaction 1 twice: 2SO22S+2O2\mathrm{2SO_2 \rightleftharpoons 2S + 2O_2}, K=1K12=10104K = \frac{1}{K_1^2} = 10^{-104}
  • Use reaction 2: 2S+3O22SO3\mathrm{2S + 3O_2 \rightleftharpoons 2SO_3}, K=K2=10129K = K_2 = 10^{129}

Adding: 2SO2+O22SO3\mathrm{2SO_2 + O_2 \rightleftharpoons 2SO_3}

Step 3 — Combined K: K=10104×10129=1025K = 10^{-104} \times 10^{129} = 10^{25}

Answer: Option (2) — 102510^{25}

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