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For the equilibrium SO3(g) ⇌ SO2(g) + 1/2 O2(g), the equilibrium constant is Kc = 4.9 × 10⁻². What is the value of Kc for the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g)?

1. 9.8 × 10⁻²
2. 4.9 × 10⁻²
3. 416
4. 2.40 × 10⁻³

Correct answer: 416

Solution

The equilibrium constant for a reaction is related to the equilibrium constant of its reverse reaction by taking the reciprocal and raising it to the power of the stoichiometric coefficients. Since the given reaction is the reverse of the original and involves doubling the coefficients, the new equilibrium constant is Kc = (1/Kc_original)², which results in 416.

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