Calculating Equilibrium Constants

Using the ICE method to solve for K

• REMEMBER! p.623• Pure Solids or Pure Liquids are not included in

equilibrium expressions because [Solids], [Liquids] are constant.

Heterogeneous Equilibrium

Calculating Equilibrium Constants• EASY when all concentrations are known!• JUST like on the quiz!

EX. For the reaction: H2(g) + I2(g) ↔ 2 HI(g)At equilibrium, the concentrations are found to be:

[H2] = 0.106 M [I2] = 0.035 M [HI] = 1.29 MK = ___[HI]2___ [H2][I2]K = ___(1.29 M)2

(0.106 M)(0.035 M)K = 4.49 x 102

What if you don’t know all equilibrium concentrations?

• USE ICE METHOD! • ICE is a simple acronym for the titles of the

first column of the table.• I stands for initial concentration.• C stands for the change in concentration.• E is for the concentration when the reaction is

at equilibrium.

Grab your example!• Turn to pg. 626 Sample Exercise 15.9• Watch This! 1.Write Balanced Equation 2.MAKE ICE BOX underneath 3.Write K Expression 4. Assign Variables5. Bring Down Stoichiometric Coefficients6. Assign Charges (- R and + P)7. Calculate Change(s)8. PLUG E back into K Expression