Equilibrium
Chapter 18
A. Reversible Reactions
• Reaction where the reactants form the products, then the products
re-form the reactants
• Use a double arrow
B. Equilibrium
• The forward and reverse reactions balance each other
• Occur at equal rates
• Concentration of products and reactants are not equal
C. Equilibrium Constant Expression
• At a given temperature, a chemical system may reach a state
in which a particular ratio of reactant and product
concentrations has a constant value
• Ratio of concentration of the products and reactants
• Only aqueous and gas species are included (not solid or liquid)
C. Equilibrium Constant Expression
• A,B,C, D are the reactants and products
• Always products over reactants
• a,b,c,d are the coefficients
• Brackets indicate molar concentration
C. Equilibrium Constant Expression
N
D. Examples
D. Examples
E. Lets add numbers…
• Calculate the value of Keq for the equilibrium
constant expression
given concentration data at one equilibrium
position: [NH3] = 0.933 mol/L, [N2] = 0.533
mol/L, [H2] = 1.600 mol/L.
E. Lets add numbers…
F. Values of Keq
• Keq > 1: More products than reactants at
equilibrium.
• Keq < 1: More reactants than products at
equilibrium.