26.07.2021 Views

General Chemistry Principles, Patterns, and Applications, 2011

General Chemistry Principles, Patterns, and Applications, 2011

General Chemistry Principles, Patterns, and Applications, 2011

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Chemical equilibrium is a dynamic process consisting of forward <strong>and</strong> reverse reactions that proceed at<br />

equal rates. At equilibrium, the composition of the system no longer changes with time. The composition<br />

of an equilibrium mixture is independent of the direction from which equilibrium is approached.<br />

K E Y T A K E A W A Y<br />

<br />

At equilibrium, the forward <strong>and</strong> reverse reactions of a system proceed at equal rates.<br />

C O N C E PTUAL P R OBLEMS<br />

1. What is meant when a reaction is described as “having reached equilibrium”? What does this statement<br />

mean regarding the forward <strong>and</strong> reverse reaction rates? What does this statement mean regarding the<br />

concentrations or amounts of the reactants <strong>and</strong> the products?<br />

2. Is it correct to say that the reaction has “stopped” when it has reached equilibrium? Explain your answer <strong>and</strong><br />

support it with a specific example.<br />

3. Why is chemical equilibrium described as a dynamic process? Describe this process in the context of a<br />

saturated solution of NaCl in water. What is occurring on a microscopic level? What is happening on a<br />

macroscopic level?<br />

4. Which of these systems exists in a state of chemical equilibrium?<br />

a. oxygen <strong>and</strong> hemoglobin in the human circulatory system<br />

b. iodine crystals in an open beaker<br />

c. the combustion of wood<br />

d. the amount of 14 C in a decomposing organism<br />

A N S W E R<br />

1.<br />

2.<br />

3. Both forward <strong>and</strong> reverse reactions occur but at the same rate. Na + <strong>and</strong> Cl − ions continuously leave the<br />

surface of an NaCl crystal to enter solution, while at the same time Na + <strong>and</strong> Cl − ions in solution precipitate on<br />

the surface of the crystal.<br />

15.2 The Equilibrium Constant<br />

L E A R N I N G O B JE C T I V E S<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

1353

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!