Sulfur dioxide and oxygen react to form sulfur trioxide during one of the key steps in sulfuric acid synthesis. An industrial chemist studying this reaction fills a 200. mL flask with 3.9 atm of sulfur dioxide gas and 3.2 atm of oxygen gas, and when the mixture has come to equilibrium measures the partial pressure of sulfur trioxide gas to be 1.6 atm. Calculate the pressure equilibrium constant for the reaction of sulfur dioxide and oxygen at the final temperature of the mixture. Round your answer to 2 significant digits.

0.20

Explanation:

Step 1: Write the balanced equation

2 SO₂(g) + O₂(g) ⇄ 2 SO₃(g)

Step 2: Make an ICE chart

        2 SO₂(g) + O₂(g) ⇄ 2 SO₃(g)

I            3.9         3.2              0

C          -2x          -x             +2x

E        3.9-2x     3.2-x            2x

Step 3: Find the value of x

The partial pressure at equilbrium of SO₃ is 1.6 atm. Then,

2x = 1.6 atm

x = 0.80 atm

Step 4: Calculate the partial pressures at equilibrium

pSO₂ = 3.9-2(0.80) = 2.3 atm

pO₂ = 3.2-0.80 = 2.4 atm

pSO₃ = 1.6 atm

Step 5: Calculate the pressure equilibrium constant

Kp = pSO₃² / pSO₂² × pO₂

Kp = 1.6² / 2.3² × 2.4

Kp = 0.20

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