1. When do you use this?
You use Keq to find the concentration of a reversible reaction at equilibrium.
You use Q to find the concentration of a reversible reaction at a given time before equilibrium to know in which direction the reaction goes.

2. What are the definitions?
Keq: Law of mass action express the relative concentration of reactants and products at equilibrium in terms of quantity called the equilibrium constant
Q: The reaction Quotient of Keq

3. Steps/Rules
Keq: 1. Balance the equation Put the products on top and the reactants on the bottom 3.coefficients are exponents only use (g) and (aq) Use the M of reactants and products to find keq.
Keq>>1= reaction lies to the right
Keq<<1= reaction lies to the left
Keq=1 at equilibrium

4. More Steps and Rules
Q: 1. Do all for Keq Use given M at given temperature Compare with value of Keq.
Q<Keq= reaction lies to the right (product side)
Q>Keq= reaction lies to the left (reactant side)

5. A solved EXAMPLE (Keq) 2CO(g) + O2 (g) ↔ 2CO2 (g)
Keq = [CO2]^2/ [CO]^2 [O2]
(Q) COCL2(g) ↔ CO(g) Cl2(g) and Keq =170. If the concentration of CO and C2 are each 0.15M and the concentration of COCL2 is 1.1 x 10^-3 is the reaction at equilibrium?
[CO][Cl2] / [COCl2] = (.15)(.15)/1.1x10^-3 = 20
Q=20

6. Here's Something to SOLVE >:)
Keq: NH4NO3 (s) ↔ N2O(g) + H2O
Q: At 448 degrees C K= 50.5 for the reaction H2(g) + I2(g) ↔ 2HI (g), Find Q and the direction of the reaction of the reaction if [H2] = .15 M, [I2] = .175 M, [HI] = .950 M.

7. Here are the answers @_@
Keq = [N2O][H20]^2
Q= Reaction lies to the right.