Question

Concentration of hydronium ions change during dilution of an acid. For true add 0 and for false add 1.

Answer 1

When the solution of an acid is diluted then its strength decreases as there is decrease in the concentration of hydronium $\left(H_3{O}^{+}\right)$ions. Diluting with water of an acid causes lowering of concentration of hydronium ion because of adding $H_{2}O$ but there are no excess $H^{+}$ to make it $\left(H_3{O}^{+}\right)$. It means number of $\left(H_3{O}^{+}\right)$ remains same but the total volume of the solution has increased thus causing the fall in concentration of hydronium ions as concentration is quantity/volume.