Textbook Question
In Problem 14.113, you wrote a mechanism for the nitric oxide– facilitated decomposition of ozone. Does your mechanism involve a catalyst or a reaction intermediate? Explain.
Ch.14 - Chemical Kinetics
Chapter 14, Problem 124
Consider the reaction H₂(g) + I₂(g) ⇌ 2 HI(g). The reaction of a fixed amount of H₂ and I₂ is studied in a cylinder fitted with a movable piston. Indicate the effect of each of the following changes on the rate of the reaction. (b) An increase in volume at constant temperature
Verified step by step guidance1
Understand the relationship between volume and pressure: According to Boyle's Law, increasing the volume of a gas at constant temperature will decrease its pressure.
Consider the effect of pressure on reaction rate: For gaseous reactions, a decrease in pressure (due to increased volume) generally leads to a decrease in the concentration of reactants.
Apply the concept of concentration and reaction rate: The rate of a chemical reaction is often proportional to the concentration of the reactants. Lower concentration typically results in a slower reaction rate.
Relate the change to the reaction equilibrium: For the reaction H₂(g) + I₂(g) ⇌ 2 HI(g), a decrease in pressure (or increase in volume) will shift the equilibrium position according to Le Chatelier's Principle, potentially affecting the rate at which equilibrium is reached.
Summarize the effect: An increase in volume at constant temperature will likely decrease the rate of the reaction due to the reduced concentration of gaseous reactants.
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. In the context of gas reactions, changes in volume can affect the concentrations of reactants and products, prompting the system to shift in a direction that minimizes the effect of the change.
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07:32
Le Chatelier's Principle
Reaction Rate
The reaction rate refers to the speed at which reactants are converted into products in a chemical reaction. It is influenced by factors such as concentration, temperature, and volume. In gas-phase reactions, increasing the volume decreases the concentration of gaseous reactants, which can slow down the reaction rate as fewer molecules are available to collide and react.
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02:03Average Rate of Reaction
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. For the reaction H₂(g) + I₂(g) ⇌ 2 HI(g), changes in volume affect the concentrations of H₂ and I₂, which can shift the position of equilibrium but does not change the value of K unless the temperature changes.
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01:14Equilibrium Constant K
Related Practice
Textbook Question
The rate of the reaction A + B2 S AB + B is directly proportional to the concentration of B2, independent of the concentration of A, and directly proportional to the concentration of a substance C. (c) What is the role of C in this reaction? Why doesn't C appear in the chemical equation for the overall reaction?
Textbook Question
Consider the reaction H2(g) + I2(g) → 2 HI(g). The reaction of a fixed amount of H2 and I2 is studied in a cylinder fitted with a movable piston. Indicate the effect of each of the following changes on the rate of the reaction. (a) An increase in temperature at constant volume
Textbook Question
Consider the reaction H2(g) + I2(g) → 2 HI(g). The reaction of a fixed amount of H2 and I2 is studied in a cylinder fitted with a movable piston. Indicate the effect of each of the following changes on the rate of the reaction. (c) The addition of a catalyst