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Ch.15 - Chemical Equilibrium
Chapter 15, Problem 25a,b

At 1000 K, 𝐾𝑝 = 1.85 for the reaction SO2(𝑔) + 1/2 O2(𝑔) β‡Œ SO3(𝑔) (a) What is the value of Kp for the reaction SO3(𝑔) β‡Œ SO2(𝑔) + 1/2 O2(𝑔)? (b) What is the value of Kp for the reaction 2 SO2(𝑔) + O2(𝑔) β‡Œ 2 SO3(𝑔)?

Verified step by step guidance
1
To find the value of Kp for the reverse reaction SO3(g) β‡Œ SO2(g) + 1/2 O2(g), we need to take the reciprocal of the given Kp for the forward reaction. This is because the equilibrium constant for a reverse reaction is the inverse of the equilibrium constant for the forward reaction.
For part (b), we need to determine the Kp for the reaction 2 SO2(g) + O2(g) β‡Œ 2 SO3(g). This reaction is a multiple of the original reaction, specifically, it is doubled. When a reaction is multiplied by a factor, the equilibrium constant is raised to the power of that factor.
Since the original reaction is SO2(g) + 1/2 O2(g) β‡Œ SO3(g) with Kp = 1.85, and the new reaction is doubled, we raise the original Kp to the power of 2.
Thus, the Kp for the reaction 2 SO2(g) + O2(g) β‡Œ 2 SO3(g) is (Kp_original)^2.
Remember, when dealing with equilibrium constants, the direction and stoichiometry of the reaction significantly affect the value of Kp. Always consider these factors when manipulating reactions.