Equilibrium Law

Reactivity 2.3.2 - 2.3.3.

State the observation for equilibrium law

At equilibrium, the ratio of the concentrations of reactants and products each raised to their stoichiometric coefficients is constant if temperature is constant

State what the exponents in the equilibrium constant equation refer to.

Coefficient of reactants and products in a balanced equation at an equilibrium state.

State the only time when K_c changes

When temperature changes.

State three special considerations for equilibrium constants.

1. Species with constant concentrations are not written in the equilibrium constant equation (SOLIDS & LIQUIDS)

2. In solutions (aqueous), solvent concentrations are not included in the K_c expression.

3. In non-aqueous solutions (liquid + liquid), the solvents must be included in the equilibrium constant equation.

Define the equilibrium constant (K_c).

Value that shows the extent of reactions at equilibrium.

Define extent of reactions at equilibrium.

Percentage of reactants that were converted into products.

State the relationship between reactants (R) & products (P) and reactants (R) & equilibrium constant (K_c).

Inverse

State the relationship between products (P) and the equilibrium constant (K_c).

Direct

State what K_c>10³ implies.

• reaction is almost completed when an equilibrium is reached.

• more products than reactants

• the equilibrium mixture is almost only composed of products
  

State what K_c<10^-3 implies.

• The reaction is far from completion when at equilibrium.

• More reactants than products.

• The equilibrium mixture is almost only composed of reactants.

State what 10^-3< K_c<10³ implies.

• the reaction neither favors reactants nor products.

• The equilibrium mixture has almost the same concentration of reactants and products.

• [R]=[P]

State the equation for a multiple of a in a reaction using K_c.

K_c^a

State the equation for a reverse reaction using K_c.

K_c^-1

Express K_overall if the equation for a reaction consists of several steps using K₁ and K₂.

K₁K₂

Define reaction quotient (Q).

Value that shows the extent of a reaction at any given time.

State what Q>K_c implies.

Favor reverse reaction

State what K_c>Q implies.

Favor forward reaction

State what K_c=Q implies.

At the given time, the reaction is at an equilibrium.

Explain why concentration changes do not affect the value of K_c.

K_c is only measured for a reaction at an equilibrium.
THEREFORE, the concentration of reactants and products do not change or are at a constant.