Calculations Involving the Equilibrium Constant

Question 1

In the equilibrium expression each figure within a square bracket represents the concentration in mol dm-3

The units of Kc therefore depend on the form of the equilibrium expression

Some questions give the number of moles of each of the reactants and products at equilibrium together with the volume of the reaction mixture

The concentrations of the reactants and products can then be calculated from the number of moles and total volume

Answer 1

mol/volume = conc

Question 2

Steps for Kc question

Answer 2

Step 1: Calculate the concentrations of the reactants and products

Step 2: Write out the balanced chemical equation with the concentrations of beneath each substance

Step 3: Write the equilibrium constant for this reaction in terms of concentration

Step 4: Substitute the equilibrium concentrations into the expression

Step 5: Deduce the correct units for Kc