Textbook Question
The equilibrium constant Kp for the reaction PCl51g2 ∆ PCl31g2 + Cl21g2 is 3.81 * 102 at 600 K and 2.69 * 103 at 700 K.(b) How are the equilibrium amounts of reactants and products affected by (iii) addition of a catalyst?
Ch.15 - Chemical Equilibrium
Chapter 15, Problem 133
Consider the following gas-phase reaction: 2 Ag + Bg ⇌ Cg + Dg. An equilibrium mixture of reactants and products is subjected to the following changes: (a) A decrease in volume (b) An increase in temperature (c) Addition of reactants (d) Addition of a catalyst (e) Addition of an inert gas. Which of these changes affect the composition of the equilibrium mixture but leave the value of the equilibrium constant Kc unchanged? Which of the changes affect the value of Kc? Which affect neither the composition of the equilibrium mixture nor Kc?
Verified step by step guidance1
Step 1: Consider the effect of a decrease in volume. According to Le Chatelier's principle, decreasing the volume of a gas-phase reaction shifts the equilibrium towards the side with fewer moles of gas. In this reaction, the left side has 3 moles (2 A_g + B_g) and the right side has 2 moles (C_g + D_g). Therefore, a decrease in volume will shift the equilibrium to the right, affecting the composition but not the equilibrium constant Kc.
Step 2: Analyze the effect of an increase in temperature. For an endothermic reaction, increasing temperature shifts the equilibrium to the right, while for an exothermic reaction, it shifts to the left. This change affects both the composition and the value of Kc, as Kc is temperature-dependent.
Step 3: Examine the addition of reactants. Adding more reactants shifts the equilibrium to the right, according to Le Chatelier's principle, to consume the added reactants. This affects the composition of the equilibrium mixture but does not change the value of Kc.
Step 4: Consider the addition of a catalyst. A catalyst speeds up the rate at which equilibrium is reached but does not affect the position of the equilibrium or the value of Kc. Therefore, it affects neither the composition nor Kc.
Step 5: Evaluate the addition of an inert gas. Adding an inert gas at constant volume does not change the partial pressures of the reactants or products, so it does not affect the equilibrium composition or the value of Kc.
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 the concentration of reactants and products will change in response to alterations such as volume, temperature, or concentration.
Recommended video:
Guided course
07:32
Le Chatelier's Principle
Equilibrium Constant (Kc)
The equilibrium constant (Kc) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium, each raised to the power of their coefficients in the balanced equation. Changes in temperature can affect the value of Kc, while changes in concentration or volume do not alter Kc but can shift the position of equilibrium.
Recommended video:
Guided course
03:20Equilibrium Constant Expressions
Catalysts and Inert Gases
Catalysts are substances that increase the rate of a reaction without being consumed, and they do not affect the position of equilibrium or the value of Kc. Similarly, the addition of an inert gas at constant temperature and volume does not change the concentrations of the reactants or products, thus having no effect on the equilibrium composition or Kc.
Recommended video:
Guided course
01:59Catalyzed vs. Uncatalyzed Reactions
Related Practice
Textbook Question
Baking soda (sodium bicarbonate) decomposes when it is heated:2 NaHCO31s2 ∆ Na2CO31s2 + CO21g2 + H2O1g2ΔH° = + 136 kJConsider an equilibrium mixture of reactants and products in a closed container. How does the number of moles of CO2 change when the mixture is disturbed by the following:(b) Adding water vapor
Textbook Question
A platinum catalyst is used in automobile catalytic convert- ers to hasten the oxidation of carbon monoxide:2 CO1g2 + O 1g2 ∆Pt 2 CO 1g2 ΔH° = - 566 kJSuppose that you have a reaction vessel containing an equilibrium mixture of CO1g2, O21g2, and CO21g2. Under the following conditions, will the amount of CO increase, decrease, or remain the same?(e) The pressure is increased by adding O2 gas.
Textbook Question
For the reaction A2 + 2B ∆ 2 AB, the rate of the for- ward reaction is 18 M/s and the rate of the reverse reaction is 12 M/s. The reaction is not at equilibrium. Will the reaction pro-ceed in the forward or reverse direction to attain equilibrium?
Textbook Question
Consider a general, single-step reaction of the type A + B ∆ C. Show that the equilibrium constant is equal to the ratio of the rate constants for the forward and reverse reactions, Kc = kf>kr.
Textbook Question
Which of the following relative values of kf and kr results in an equilibrium mixture that contains large amounts of reactants and small amounts of products? (a) kf 7 kr (b) kf = kr (c) kf 6 kr
1
views