Which statement is true for a solution when its concentration of hydronium ions increases?
it becomes less acidic.
its ph value increases.
its ph value decreases.
it becomes more alkaline.

Its pH value decreases.

Explanation: pH is the measure of acidity or alkalinity of a solution.

pH is calculated by taking negative logarithm of hydronium ion concentration. Acids have pH ranging from 1 to 6.9 and bases have pH ranging from 7.1 to 14.

Thus as pH and are inversely related, a solution having lower pH will have more amount of concentration. And a solution having more pH will have less amount of concentration.

Thus when concentration of hydronium ions increases, the pH of the solution decreases and the solution becomes more acidic.