Which one of the following expressions can be used to calculate the value of the equilibrium constant for this reaction? A - VCE - SSCE Chemistry - Question 3 - 2011 - Paper 1

To determine the correct expression for the equilibrium constant (K), we need to use the formula that reflects the relationship between the concentrations of the products and the reactants at equilibrium. The expression should be in the form of:

$K = \frac{[\text{products}]}{[\text{reactants}]}$.

In this case, since HF is a product and H2 and F2 are reactants, the expression must correctly consider their concentrations raised to the power of their respective stoichiometric coefficients in the balanced reaction.

The correct answer is D:

$K = \frac{n(HF)}{n(H_2)^{\frac{1}{2}} \cdot n(F_2)^{\frac{1}{2}}}$