This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: 628 Chapter Thirteen Chemical Equilibrium how is the value of K p for the reversed reaction related to the value of K p for the initial reaction? 5. What are homogeneous equilibria? Heterogeneous equilibria? What is the differ ence in writing K expressions for homogeneous versus heterogeneous reactions? Summarize which species are included in the K expression and which species are not included. 6. Distinguish between the terms equilibrium constant and reaction quotient. When Q K , what does this say about a reaction? When Q K , what does this say about a reaction? When Q K , what does this say about a reaction? 7. Summarize the steps for solving equilibrium problems (see the beginning of Sec tion 13.6). In general, when solving an equilibrium problem, you should always set up an ICE table. What is an ICE table? 8. A common type of reaction we will study is that having a very small K value ( K V 1). Solving for equilibrium concentrations in an equilibrium problem usu ally requires many mathematical operations to be performed. However, the math involved when solving equilibrium problems for reactions having small K values ( K V 1) is simplified. What assumption is made when solving the equilibrium concentrations for reactions with small K values? Whenever assumptions are made, they must be checked for validity. In general, the “5% rule” is used to check the validity of assuming x (or 2 x , 3 x , and so on) is very small compared to some num ber. When x (or 2 x , 3 x , and so on) is less than 5% of the number the assumption was made against, then the assumption is said to be valid. If the 5% rule fails, what do you do to solve for the equilibrium concentrations? 9. What is Le Châtelier’s principle? Consider the reaction 2NOCl( g ) Δ 2NO( g ) Cl 2 ( g ). If this reaction is at equilibrium, what happens when the following changes occur? a. NOCl( g ) is added. b. NO( g ) is added. c. NOCl( g ) is removed. d. Cl 2 ( g ) is removed. e. The container volume is decreased. For each of these changes, what happens to the value of K for the reaction as equi librium is reached again? Give an example of a reaction for which the addition or re moval of one of the reactants or products has no effect on the equilibrium position. In general, how will the equilibrium position of a gasphase reaction be af fected if the volume of the reaction vessel changes? Are there reactions that will not have their equilibria shifted by a change in volume? Explain. Why does chang ing the pressure in a rigid container by adding an inert gas not shift the equilib rium position for a gasphase reaction? 10. The only “stress” (change) that also changes the value of K is a change in temper ature. For an exothermic reaction, how does the equilibrium position change as temperature increases, and what happens to the value of K ? Answer the same ques tions for an endothermic reaction. If the value of K increases with a decrease in temperature, is the reaction exothermic or endothermic? Explain.temperature, is the reaction exothermic or endothermic?...
View
Full Document
 Fall '07
 ZOLLER,WILLIAMH
 Chemistry, Equilibrium, Reaction

Click to edit the document details