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Ch.15 - Chemical Equilibrium
McMurry - Chemistry 8th Edition
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Tutti i libri di testoMcMurry 8th EditionCh.15 - Chemical EquilibriumProblema 123
Capitolo 15, Problema 123

The value of ΔH° for the reaction 3 O2(g) ⇌ 2 O3(g) is +285 kJ. Does the equilibrium constant for this reaction increase or decrease when the temperature increases? Justify your answer using Le Châtelier’s principle.

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Step 1: Understand the reaction and the given information. The reaction is 3 O2(g) ⇌ 2 O3(g) with a ΔH° of +285 kJ, indicating that the reaction is endothermic (absorbs heat).
Step 2: Recall Le Châtelier’s principle, which states that if a system at equilibrium is subjected to a change in temperature, pressure, or concentration, the system will adjust to counteract the change and restore a new equilibrium.
Step 3: Consider the effect of temperature on an endothermic reaction. For an endothermic reaction, increasing the temperature adds heat to the system, which can be considered as a reactant.
Step 4: Apply Le Châtelier’s principle. Since the reaction is endothermic, increasing the temperature will shift the equilibrium to the right, favoring the formation of products (O3) to absorb the added heat.
Step 5: Relate the shift in equilibrium to the equilibrium constant (K). As the equilibrium shifts to the right, the concentration of products increases relative to reactants, leading to an increase in the equilibrium constant (K) with an increase in temperature.

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Enthalpy (ΔH°)

Enthalpy, represented as ΔH°, is a measure of the total heat content of a system at constant pressure. A positive ΔH° indicates that the reaction is endothermic, meaning it absorbs heat from the surroundings. In the given reaction, the formation of ozone (O3) from oxygen (O2) requires energy, which is reflected in the positive value of +285 kJ.
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Enthalpy of Formation

Le Châtelier’s Principle

Le Châtelier’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. In the context of temperature changes, if the temperature is increased for an endothermic reaction, the system will shift to favor the formation of products to absorb the added heat, thereby increasing the equilibrium constant.
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Le Chatelier's Principle

Equilibrium Constant (K)

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. For the reaction 3 O2(g) ⇌ 2 O3(g), an increase in temperature shifts the equilibrium towards the products (O3) due to the endothermic nature of the reaction, resulting in a higher value of K as the concentration of O3 increases relative to O2.
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Equilibrium Constant K
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