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Ch.15 - Chemical Equilibrium
All textbooksMcMurry 8th EditionCh.15 - Chemical EquilibriumProblem 99
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Chapter 15, Problem 99

The reaction of iron(III) oxide with carbon monoxide is important in making steel. At 1200 K, Kp = 19.9 for the reaction Fe2O3(s) + 3 CO(g) ⇌ 2 Fe(l) + 3 CO2(g). What are the equilibrium partial pressures of CO and CO2 if CO is the only gas present initially, at a partial pressure of 0.978 atm?

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1
Identify the balanced chemical equation: Fe2O3(s) + 3 CO(g) ⇌ 2 Fe(l) + 3 CO2(g). Note that solids and liquids do not appear in the expression for Kp.
Write the expression for the equilibrium constant Kp: Kp = (P_CO2^3) / (P_CO^3), where P_CO2 and P_CO are the equilibrium partial pressures of CO2 and CO, respectively.
Set up an ICE (Initial, Change, Equilibrium) table to track the changes in partial pressures. Initially, P_CO = 0.978 atm and P_CO2 = 0 atm.
Define the change in partial pressure of CO as -3x and the change in partial pressure of CO2 as +3x, where x is the change in moles of CO2 formed.
Substitute the equilibrium expressions from the ICE table into the Kp expression: 19.9 = ((3x)^3) / ((0.978 - 3x)^3). Solve for x to find the equilibrium partial pressures of CO and CO2.
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