Chemistry / Unit 10 Chem 1768 worked example, 60 to 90 seconds
The ICE Table Method
The idea
Solving an equilibrium problem with an ICE table means recording each species' Initial concentration, its Change expressed as a multiple of an unknown x using stoichiometric coefficients, and the resulting Equilibrium concentration, then substituting the equilibrium row into the K expression and solving for x.
In practice
For H2 + I2 ⇌ 2 HI, K = 54.3, starting from 1.00 M each of H2 and I2 and no HI, the ICE table gives equilibrium concentrations (1.00 − x), (1.00 − x), and 2x. Substituting into K = (2x)²/[(1.00 − x)(1.00 − x)] and solving yields x ≈ 0.786, so [HI] at equilibrium is about 1.57 M.
Where people slip
Forgetting that a coefficient of 2 multiplies x in the Change row, not only in the Equilibrium row, produces equilibrium concentrations that do not satisfy the balanced equation.
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