CHM 2046C  Module 10-Chapter 16 Answers

Part C: The Equilibrium Constant K & Expression    10 points

   a A  + b B ß à c C   + d D

                                                                           [C]c [D]d

Equilibrium Constant =       K  =  ---------------

                                                                           [A]a [B]b

 

Write five statements which explain what the equilibrium constant expression represents:

 

a) All concentrations are equilibrium values

 

b) Product concentrations appear in the numerator and the reactant concentrations appear in the denominator

 

c) Each concentration is raised to the power of its stoichiometric coefficient in the balanced chemical equation

 

d) The value of K depends on a particular reaction and on the temperature

 

e) Units are never given with K

 

Write five useful statements about the equilibrium constant:

 

a) If the ration of the products to the reactants as define in the equilibrium constant expression matches the equilibrium constant value, the system is said to be at equilibrium. Conversely, if the ratio has a different value, the system is not at equilibrium, and we can predict in which direction the reaction will proceed to reach equilibrium.

 

b) The equilibrium constant value indicates whether a reaction is product-favored or reactant-favored.

 

c) If some concentrations of reactants or products are known at equilibrium, others can be calculated from the equilibrium constant expression.

 

d) If the initial concentration and the value of K are known, the concentration of reactants and products at equilibrium can be calculated

 

e) The equilibrium expressions do not contain concentration terms for species in a phase different from that in which the equilibrium exists, such as gases or solids in a solution equilibrium..

 

f) Solution equilibrium expressions do not include the concentration of the solvent, such as an aqueous solution does not include the concentration of water.

 

g) When the stoichiometric coefficients of a balanced equation are multiplied by some factor, the equilibrium constant for the new equation (Knew) is the old equilibrium constant (Kold) raised to the power of the multiplication factor

 

h) The equilibrium constant for a reaction and its reverse are reciprocals of each other.

 

See page 762, 763, 778.