In a mixture of strong and weak acid, the strong acid dissociates completely, significantly elevating H3O+ ion concentration, while the weak acid only partially dissociates. Le Châtelier's principle explains that the stronger acid suppresses the weaker acid's dissociation by shifting the equilibrium towards the reactants. Consider a mixture of 0.15 M HCl and 0.30 M HCN. The strong acid yields a H3O+ concentration of 0.15 M, making the H3O+ concentration from the weak acid negligible. So, the pH in a mixture of acids is predominantly dictated by the concentration of the strong acid. Similarly, when a mixture of two weak acids of equal amounts is present, the relatively stronger acid is the primary pH determinant. For example, in a mixture of HF and HCN, HF will be the major determinant of the mixture's pH, as it has a Ka of 3.5 × 10−4 which is almost a million times higher than the Ka of hydrocyanic acid.