Copyright ©2009 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Introductory Chemistry, Third Edition By Nivaldo J. Tro EXAMPLE 15.5 The Effect of a Concentration Change on Equilibrium FOR MORE PRACTICE Example 15.13a, b; Problems 65, 66, 67, 68. What is the effect of removing Br 2 some from the preceding reaction mixture? SKILLBUILDER PLUS Consider the following reaction at equilibrium. What is the effect of adding additional CO 2 to the reaction mixture? What is the effect of adding additional CaCO 3. Solution : Adding additional CO 2 increases the concentration of CO 2 and causes the reaction to shift to the left. Adding additional CaCO 3 does not increase the concentration of CaCO 3 because CaCO 3 is a solid and thus has a constant concentration. It is therefore not included in the equilibrium expression and has no effect on the position of the equilibrium. Consider the following reaction in chemical equilibrium. What is the effect of adding additional Br 2 to the reaction mixture? What is the effect of adding additional BrNO? SKILLBUILDER 15.5 The Effect of a Concentration Change on Equilibrium

Copyright ©2009 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Introductory Chemistry, Third Edition By Nivaldo J. Tro EXAMPLE 15.6 The Effect of a Volume Change on Equilibrium FOR MORE PRACTICE Example 15.13c; Problems 69, 70, 71, 72. Consider the following reaction at chemical equilibrium. What is the effect of decreasing the volume of the reaction mixture? Increasing the volume of the reaction mixture? Solution : The chemical equation has 3 mol of gas on the right and 0 mol of gas on the left. Decreasing the volume of the reaction mixture increases the pressure and causes the reaction to shift to the left (toward the side with fewer moles of gas particles). Increasing the volume of the reaction mixture decreases the pressure and causes the reaction to shift to the right (toward the side with more moles of gas particles). Consider the following reaction in chemical equilibrium. What is the effect of decreasing the volume of the reaction mixture? Increasing the volume of the reaction mixture? SKILLBUILDER 15.6 The Effect of a Volume Change on Equilibrium

Copyright ©2009 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Introductory Chemistry, Third Edition By Nivaldo J. Tro EXAMPLE 15.7 The Effect of a Volume Change on Equilibrium FOR MORE PRACTICE Example 15.13d; Problems 73, 74, 75, 76. The following reaction is endothermic. What is the effect of increasing the temperature of the reaction mixture? Decreasing the temperature? Solution : Since the reaction is endothermic, we can think of heat as a reactant. Raising the temperature is adding heat, causing the reaction to shift to the right. Lowering the temperature is removing heat, causing the reaction to shift to the left. The following reaction is exothermic. What is the effect of increasing the temperature of the reaction mixture? Decreasing the temperature? SKILLBUILDER 15.7 The Effect of a Volume Change on Equilibrium

Copyright ©2009 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Introductory Chemistry, Third Edition By Nivaldo J. Tro EXAMPLE Using LeChâtelier’s Principle Solution : (a) Shift left (b) Shift right (c) Shift right (more moles of gas on right) (d) Shift right (heat is a reactant) Consider the following endothermic chemical reaction. Predict the effect of: (a) increasing [CO] (b) Increasing [H 2 O] (c) increasing the reaction volume (d) increasing the temperature