Question

The following table lists the pH values of some acids and bases.

Solutions	pH
Hydrochloric acid	$1$
Milk	$6$
Pure water	$7$
Baking soda	$9$
Sodium hydroxide	$14$

What would happen to the pH of an acid and a base when each is diluted (pure distilled water is added to it)?

• A. On dilution, the pH of an acid and base will both decrease
• B. On dilution, the pH of an acid will increase and that of a base will decrease
• C. On dilution, the pH of an acid and base will both increase
• D. On dilution, the pH of an acid will decrease and that of a base will increase

Answer 1

Answer: (B)

On dilution, the pH of an acid will increase and that of a base will decrease

On dilution, the pH of an acid will increase and that of a base will decrease. The acidity of a solution increases as concentration of $H_3{O}^{+}$ increases in aqueous acidic solution and so pH decreases. Opposite to this, as the concentration of $H_3{O}^{+}$ decreases, the acidity of the solution decreases and so, pH increases.