Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458

All rights reserved.

Introductory Chemistry, Third EditionBy 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 Br2 some from the preceding reaction mixture?

SKILLBUILDER PLUS

Consider the following reaction at equilibrium.

What is the effect of adding additional CO2 to the reaction mixture? What is the effect of adding additional CaCO3. Solution:Adding additional CO2 increases the concentration of CO2 and causes the reaction to shift to the left. Adding additional CaCO3 does not increase the concentration of CaCO3 because CaCO3 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 Br2 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 07458

All rights reserved.

Introductory Chemistry, Third EditionBy 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 molesof 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 07458

All rights reserved.

Introductory Chemistry, Third EditionBy 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 07458

All rights reserved.

Introductory Chemistry, Third EditionBy Nivaldo J. Tro

EXAMPLE 15.13 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 [H2O](c) increasing the reaction volume(d) increasing the temperature