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Ch.15 - Chemical Equilibrium
All textbooksMcMurry 8th EditionCh.15 - Chemical EquilibriumProblem 129
Chapter 15, Problem 129

For the following reaction catalyzed by iridium, which is endothermic at 700 K: CaO(s) + CH₄(g) + 2 H₂O(g) ⇌ CaCO₃(s) + 4 H₂(g), how would the following changes affect the total quantity of CaCO₃ in the reaction mixture once equilibrium is reestablished at 700 K? (a) Increasing the temperature (b) Adding calcium oxide (c) Removing methane (CH₄) (d) Adding iridium.

Verified step by step guidance
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Step 1: Understand the nature of the reaction. The reaction is endothermic, meaning it absorbs heat. According to Le Chatelier's principle, increasing the temperature will favor the endothermic direction, which is the forward reaction in this case, increasing the amount of CaCO₃.
Step 2: Consider the effect of adding calcium oxide (CaO). Adding a reactant will shift the equilibrium to the right, towards the products, to counteract the change, thus increasing the amount of CaCO₃.
Step 3: Analyze the impact of removing methane (CH₄). Removing a reactant will shift the equilibrium to the left, towards the reactants, to replace the removed substance, thus decreasing the amount of CaCO₃.
Step 4: Evaluate the role of adding iridium. Iridium is a catalyst, which speeds up the rate at which equilibrium is reached but does not affect the position of the equilibrium. Therefore, adding iridium will not change the amount of CaCO₃ at equilibrium.
Step 5: Summarize the effects: (a) Increasing temperature increases CaCO₃, (b) Adding CaO increases CaCO₃, (c) Removing CH₄ decreases CaCO₃, (d) Adding iridium has no effect on CaCO₃ at equilibrium.

Key Concepts

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

Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change. This principle helps predict how a system at equilibrium will respond to changes in concentration, temperature, or pressure, thereby affecting the amounts of reactants and products present.
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Le Chatelier's Principle

Endothermic Reactions

An endothermic reaction is one that absorbs heat from its surroundings. In the context of the given reaction, increasing the temperature will favor the formation of products, as the system will shift to absorb the added heat, thus potentially increasing the quantity of CaCO₃ produced at equilibrium.
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Endothermic & Exothermic Reactions

Catalysts and Equilibrium

A catalyst, such as iridium in this reaction, speeds up the rate of both the forward and reverse reactions without being consumed. While it helps the system reach equilibrium faster, it does not affect the position of equilibrium or the total quantities of reactants and products at equilibrium.
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Related Practice
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