1. “Products over reactants, the coefficients are the powers”
The Equilibrium Law
“Products over reactants, the coefficients are the powers”

2. equilibrium constant OUTCOME QUESTION(S): C12-4-04 EQUILIBRIUM AND Keq
Relate the concept of equilibrium to physical and chemical systems.
Include: conditions necessary to achieve equilibrium.
Write equilibrium law expressions from balanced chemical equations and solve problems involving equilibrium constants.
Include: ICE tables
Vocabulary & Concepts
equilibrium constant 

3. aA + bB cC + dD Keq Equilibrium Law
For a system at equilibrium (with constant temperature), a ratio of the concentrations of reactants over products raised to the coefficients of the equation equal a constant value.
aA + bB cC + dD
This new expression is connected to what we know about elementary reactions and rate kinetics… =
Keq
[A]a[B]b
[C]c[D]d

4. Keq kf [A]a[B]b = kr [C]c[D]d
For an elementary reaction, the forward and reverse reactions would have these rate laws:
aA + bB cC + dD
ratefwd = kf [A]a[B]b
raterev = kr [C]c[D]d
And at equilibrium rates are equal: kf kr =
[A]a[B]b
[C]c[D]d
Keq
kf [A]a[B]b = kr [C]c[D]d
Rearranged we get…
The ratio of rate constants was condensed to one constant, Keq, called the equilibrium constant.

5. “Products over reactants, the coefficients are the powers”
When writing the equilibrium expression, omit solids (s) or liquids (l).
Solids and Liquids don’t have concentrations, they have density – which is accounted for in the constant value
C(s) + H2O(g) CO(g) + H2(g)
The constant is generally abbreviated Keq
Kc is using concentrations
Kp is when using pressures =
[CO][H2]
[H2O] Kc
{C}

6. “Products over reactants, the coefficients are the powers”
Write the equilibrium expressions:
N2 (g) + 3 H2 (g) NH3 (g) = Kc
[N2][H2]3
[NH3]2
2 Na(s) + Pb2+(aq) Pb(s) + 2 Na1+(aq) = Kc
[Pb2+]
[Na1+]2
Homogeneous equilibria
Reactants and products are all in one state
Heterogeneous equilibria
Reactants and products in more than one state

7. If Kc = 1 [products] = [reactants]
Keq value can indicate whether there are more products or reactants when equilibrium is reached:
If Kc = 1 [products] = [reactants]
aA + bB cC + dD
Kinetic Region
Equilibrium Region
Kinetic Region
Equilibrium Region
Concentration
Rate
Reactants
Reactants
Products
Products
Time
teqbm
Time
teqbm

8. If Kc > 1 [products] are favoured.
Keq value can indicate whether there are more products or reactants when equilibrium is reached:
If Kc > 1 [products] are favoured.
aA + bB cC + dD
Kinetic Region
Equilibrium Region
Kinetic Region
Equilibrium Region
Concentration
Rate
Reactants
Reactants
Products
Products
Time
teqbm
Time
teqbm

9. If Kc < 1 [reactants] are favoured.
Keq value can indicate whether there are more products or reactants when equilibrium is reached:
If Kc < 1 [reactants] are favoured.
aA + bB cC + dD
Kinetic Region
Equilibrium Region
Kinetic Region
Equilibrium Region
Concentration
Rate
Reactants
Reactants
Products
Products
Time
teqbm
Time
teqbm

10. equilibrium constant CAN YOU / HAVE YOU? C12-4-04 EQUILIBRIUM AND Keq
Relate the concept of equilibrium to physical and chemical systems.
Include: conditions necessary to achieve equilibrium.
Write equilibrium law expressions from balanced chemical equations and solve problems involving equilibrium constants.
Include: ICE tables
Vocabulary & Concepts
equilibrium constant