Calculations With Equilibrium Constant
The Kc Constant
The equilibrium constant is a mathematical representation of the ratio of products to reactants when a system is at equilibrium. In simpler terms (and not quite technically accurate), the Kc is a constant number for a chemical reaction. It is a number that is always the same for a specific chemical reaction, and it compares the amount of products to the amount of reactants when the chemical reaction is at equilbrium.
Because of this, it is important to be able to:
1) determine the Kc for a reaction, given the equilibrium concentrations of all the materials within the reaction, and
2) determine the concentrations of the materials, given the equilibrium constant.
Because we need to be able to do both, let's practice each one.
Example 1:
The equilibrium constant is a mathematical representation of the ratio of products to reactants when a system is at equilibrium. In simpler terms (and not quite technically accurate), the Kc is a constant number for a chemical reaction. It is a number that is always the same for a specific chemical reaction, and it compares the amount of products to the amount of reactants when the chemical reaction is at equilbrium.
Because of this, it is important to be able to:
1) determine the Kc for a reaction, given the equilibrium concentrations of all the materials within the reaction, and
2) determine the concentrations of the materials, given the equilibrium constant.
Because we need to be able to do both, let's practice each one.
Example 1:
For the reaction:
H2 (g) + I2 (g) <==> 2 HI (g)
the equilibrium concentrations are [H2] = 0.95 M, [I2] = 0.95 M and [HI] = 7.1 M at 20 0C. What is the equilibrium constant for the reaction?
Example 2:
At 500 OC, the Kc for the synthesis of ammonia (NH3) is 0.0602. If at equilibrium, the [N2] = 0.399 M and the [NH3] = 0.203 M. What is the equilibrium concentration of hydrogen ?