Final answer:
Increasing the concentration of an acid in a solution results in an increased concentration of hydronium ions ([H₃O⁺]) at equilibrium.
Step-by-step explanation:
Increasing the initial concentration of acid results in increased [H₃O⁺] at equilibrium. This is because when more acid is added to a solution, it dissociates to release more H₃O⁺ ions, which increases the hydronium ion concentration.
In accordance with Le Chatelier's principle, adding more of a reactant to a system at equilibrium will shift the reaction to the right (towards the production of products), thereby increasing the concentration of the product, which in this case is H₃O⁺.