Calculating Equilibrium Concentrations: the ICE table
When reversible reactions achieve equilibrium before all the reactants become products, stoichiometry is more difficult. To do these calculations we use an “ICE table”
Example #1:
Hydrogen fluoride forms from its elements at SATP:
If the reaction begins with 1.00mol/L concentrations of both H
2(g) and
F
2(g) and no HF
(g)
, calculate the concentrations of H
2(g) and HF
(g) at equilibrium if the equilibrium concentration of F
2(g) is measured to be
0.24mol/L.
1. Set up ICE table:
2. x = change in concentration of reactants and products. Coefficients correspond to those in the balanced equation.
3. Final concentrations of reactants = initial concentrations - change in conc. Final concentrations of products = initial concentrations plus change in conc.
4. Use F
2(g) at equil = 0.24mol/L, to solve for x:
5. Use x values to solve for two missing equilibrium concentrations:

Example #2:
When ammonia is heated, it decomposes into nitrogen gas and hydrogen gas.
When 4.0 mol of ammonia is introduced into a 2.0L rigid container and heated to a particular temperature, the amount of ammonia changes as shown in the figure.

Example #3:
In a gaseous reaction system, 0.200mol of hydrogen gas is added to
0.200mol of iodine gas in a rigid 2.00L container at 448°C. At equilibrium, the sytem contains 0.040mol of hydrogen. Determine equilibrium concentrations of hydrogen and iodine.