Question

While diluting an acid, why is it recommended that the acid should be
added to water and not water to the acid?
How is the concentration of hydronium ions (HO) affected when a
solution of an acid is diluted?
How is the concentration of hydroxide ions (OH) affected when excess
base is dissolved in a solution of sodium hydroxide?​

Answer 1

Explanation:

When the solution of an acid is diluted then its strength decreases as there is a decrease in the concentration of hydronium (H3O+ )ions. Diluting with water of acid causes lowering of the concentration of hydronium ion because of adding H2O but there is no excess H+ to make it (H3O+). It means a number of (H3O+) remains the same but the total volume of the solution has increased thus causing the fall in the concentration of hydronium ions as concentration is quantity/volume.