How is the concentration of hydronium ions (H₃O⁺) affected when a solution of an acid is diluted?
When a solution of an acid is diluted, the concentration of hydronium ions (H₃O⁺) decreases per unit volume. This happens because mixing an acid with water results in a decrease in the concentration of ions per unit volume, which is the process called dilution.
As the concentration of hydronium ions decreases, the pH value increases. This is because higher the hydronium ion concentration, lower is the pH value. Therefore, the diluted acid becomes less acidic than the concentrated acid.
Explanation
This question directly relates to the concept of dilution explained in the textbook. The context clearly states that 'Mixing an acid or base with water results in decrease in the concentration of ions (H₃O⁺/OH⁻) per unit volume.' It also establishes the relationship that 'Higher the hydronium ion concentration, lower is the pH value.' Students should understand that dilution spreads the same number of H₃O⁺ ions over a larger volume, thus decreasing their concentration per unit volume.