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Ch.15 - Chemical Equilibrium
Chapter 15, Problem 62a,b,c

Consider the reaction 4 NH3(𝑔) + 5 O2(𝑔) β‡Œ 4 NO(𝑔) + 6 H2O(𝑔), Δ𝐻 = βˆ’904.4 kJ Does each of the following increase, decrease, or leave unchanged the yield of NO at equilibrium? (a) increase [NH3] (b) increase [H2O] (c) decrease [O2]

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1
Identify the type of reaction: The given reaction is an exothermic reaction, as indicated by the negative Ξ”H value (-904.4 kJ).
Apply Le Chatelier's Principle: This principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change.
Consider the effect of decreasing [O_2]: According to Le Chatelier's Principle, decreasing the concentration of a reactant will shift the equilibrium position to the left to produce more reactants.
Analyze the impact on NO yield: Since the equilibrium shifts to the left, the yield of NO will decrease as the system tries to produce more NH_3 and O_2.
Conclude the effect: Therefore, decreasing the concentration of O_2 will decrease the yield of NO at equilibrium.

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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 system will adjust to counteract the change and restore a new equilibrium. This principle helps predict how changes in concentration, pressure, or temperature will affect the position of equilibrium in a chemical reaction.
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Equilibrium Constant (K)

The equilibrium constant (K) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. Changes in concentration of reactants or products can shift the equilibrium position, affecting the yield of products like NO in the given reaction.
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Reaction Stoichiometry

Reaction stoichiometry involves the quantitative relationships between the reactants and products in a chemical reaction, as described by the balanced equation. Understanding stoichiometry is essential for predicting how changes in the concentration of one reactant, such as O2, will impact the amounts of products formed, including NO.
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