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Ch.15 - Chemical Equilibrium
Chapter 15, Problem 87

NiO is to be reduced to nickel metal in an industrial process using the reaction NiO(s) + CO(g) ⇌ Ni(s) + CO2(g). At 1600 K, the equilibrium constant for the reaction is Kp = 6.0 × 10^2. If a CO pressure of 150 torr is to be employed in the furnace and the total pressure never exceeds 760 torr, will reduction occur?

Verified step by step guidance
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Step 1: Write the expression for the equilibrium constant Kp for the reaction. For the reaction NiO(s) + CO(g) ⇌ Ni(s) + CO2(g), the expression is Kp = (P_CO2) / (P_CO), where P_CO2 and P_CO are the partial pressures of CO2 and CO, respectively.
Step 2: Identify the given values. You are given Kp = 6.0 × 10^2 and the pressure of CO, P_CO = 150 torr. The total pressure is not to exceed 760 torr.
Step 3: Calculate the partial pressure of CO2, P_CO2, using the equilibrium constant expression. Rearrange the expression to find P_CO2 = Kp × P_CO.
Step 4: Check if the calculated P_CO2, when added to the given P_CO, exceeds the total pressure limit of 760 torr. If P_CO2 + P_CO ≤ 760 torr, the reduction will occur under the given conditions.
Step 5: Conclude whether the reduction of NiO to Ni will occur based on the comparison of the calculated total pressure with the maximum allowable pressure.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Equilibrium Constant (Kp)

The equilibrium constant (Kp) quantifies the ratio of the partial pressures of products to reactants at equilibrium for a given reaction. For the reaction NiO(s) + CO(g) ⇌ Ni(s) + CO2(g), Kp = 6.0 × 10^2 indicates that at equilibrium, the products (Ni and CO2) are favored over the reactants (NiO and CO). This value helps determine whether the reaction will proceed in the forward direction under specific conditions.
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Le Chatelier's Principle

Le Chatelier's Principle states that if a system at equilibrium is subjected to a change in concentration, pressure, or temperature, the system will adjust to counteract that change and restore a new equilibrium. In this context, increasing the pressure of CO or changing the total pressure can shift the equilibrium position, potentially favoring the reduction of NiO to Ni.
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Partial Pressure and Total Pressure

Partial pressure refers to the pressure exerted by a single component of a gas mixture, while total pressure is the sum of the partial pressures of all gases present. In this scenario, the CO pressure is 150 torr, and the total pressure is limited to 760 torr. Understanding these pressures is crucial for calculating the reaction quotient (Q) and comparing it to Kp to determine if the reduction of NiO will occur.
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