Chemical Equilibrium Calculation Example with Reactant Concentration

How can we calculate the equilibrium concentration of a reactant in a chemical reaction?

Given the equilibrium constant K = 6.3 × 10−4 for the reaction 2HF ⇌ H₂+F₂ and initial concentrations of 0.60 mol HF, 0.20 mol H₂, and 0.20 mol F₂ in a 4.0-liter container, how can we determine the equilibrium concentration of H₂?

Equilibrium Concentration Calculation:

With an equilibrium constant K = 6.3 × 10−4 for the reaction 2HF ⇌ H₂+F₂ and initial concentrations of 0.60 mol HF, 0.20 mol H₂, and 0.20 mol F₂ in a 4.0-liter container, the equilibrium concentration of H₂ can be calculated as follows:

Explanation:

This scenario involves a chemical reaction at equilibrium where the equilibrium constant (K) is known. In this case, the equilibrium constant is 6.3 × 10−4 for the reaction 2HF ⇌ H₂+F₂.

Given the initial concentrations of the reactants in the 4.0-liter container, we can convert the moles to concentrations by dividing by the volume of the container. The concentrations are as follows: [HF] = 0.60 mol/4.0 L = 0.15 M, [H₂] = 0.20 mol/4.0 L = 0.05 M, and [F₂] = 0.20 mol/4.0 L = 0.05 M.

Using the equilibrium constant expression K = [H₂][F₂]/([HF]²), we substitute the concentrations to find that the equilibrium concentration of H₂ is 0.05 M.

This equilibrium concentration indicates that the reaction remains unchanged from its initial state due to the small value of the equilibrium constant K.