In the gas phase at 400 °C, isopropyl alcohol (rubbing alcohol) decomposes to acetone, an important industrial solvent: \[\text{Isopropyl alcohol: }(\text{CH}_3)_2\text{CHOH(g)} \rightleftharpoons (\text{CH}_3)_2\text{CO(g) + H}_2\text{(g)} \\\Delta H^\circ = + 57.3 \text{ kJ}\]Does the amount of acetone increase, decrease, or remain the same when an equilibrium mixture of reactants and products is subjected to the following changes?(c) Argon is added.(d) H₂ is added.(e) A catalyst is added.
Verified step by step guidance
1
Step 1: Understand the equilibrium reaction: Isopropyl alcohol decomposes into acetone and hydrogen gas. The reaction is endothermic, as indicated by the positive \( \Delta H^\circ \).
Step 2: Consider the effect of adding argon (c): Argon is an inert gas and does not participate in the reaction. Adding argon at constant volume does not change the partial pressures of the reactants or products, so the equilibrium position remains unchanged.
Step 3: Analyze the effect of adding H₂ (d): Adding more H₂ increases its partial pressure, shifting the equilibrium to the left according to Le Chatelier's principle, which will decrease the amount of acetone.
Step 4: Evaluate the effect of adding a catalyst (e): A catalyst speeds up the rate at which equilibrium is reached but does not affect the position of the equilibrium. Therefore, the amount of acetone remains the same.
Step 5: Summarize the effects: (c) Adding argon does not change the amount of acetone, (d) adding H₂ decreases the amount of acetone, and (e) adding a catalyst does not change the amount of acetone.
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 itself to counteract the change and restore a new equilibrium. This principle helps predict how the concentration of reactants and products will shift in response to changes in concentration, pressure, or temperature.
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 or pressure can affect the position of equilibrium, but the value of K remains constant unless the temperature changes.
A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. While catalysts speed up the attainment of equilibrium, they do not affect the position of the equilibrium or the concentrations of reactants and products at equilibrium; they simply allow the system to reach equilibrium faster.
07:32
