# 15.1 Equilibrium and Equilibrium Constants ## Equilibrium

The rate of the forward reaction equals the rate of the reverse reaction.
Concentrations of reactants and products are not changing.

## Equilibrium Constants (Law of Mass Action)

-Equals the ratio of the concentrations of products to the concentrations of reactants at equilibrium raised to the power of their coefficients.
-Only aqueous and gaseous species are included.
-Equilibrium constants are CONSTANTS; the value will only change with a change in temperature.
-An equilibrium constant also equals the ratio of the forward and reverse rate constants.

EQUILIBRIUM CONSTANTS
K >> 1 Favors Products
K << 1 Favors Reactants
10-3 < K < 103 Reactants and products
both present at equilibrium 2C(s) + O2(g) ⇌ 2CO(g)
Write the equilibrium constant expression (Kc and Kp) for the reaction above.

## Kp vs Kc

Kp = Kc (RT)Δn          Δn = change in moles gas          R = 0.0821 L•atm/mol•K

If for 2C(s) + O2(g) ⇌ 2CO(g) Kc = 1200 at 400K, then what is the value of Kp?

## 2SO2(g) + O2(g) ⇌ 2SO3(g)      Kc = 4.0

Based on the reaction above, what are the equilibrium constants for the following reactions?

2SO3(g) ⇌ 2SO2(g) + O2(g)

SO2(g) + ½O2(g) ⇌ SO3(g)

SO3(g) ⇌ SO2(g) + ½O2(g)