Question

As [H₃O⁺] increases, [OH⁻] must ________.

a) Decrease
b) Increase
c) Remain constant
d) No definite relationship

Answer 1

As hydronium ion concentration increases, hydroxide ion concentration must decrease due to the inverse relationship dictated by the water dissociation constant.

Step-by-step explanation:

As [H₃O⁺] increases, [OH⁻] must decrease. This relationship is due to the constant nature of the water dissociation constant (Kw) at a given temperature, which for pure water at 25°C is 1.0 × 10⁻¹⁴ M².

According to the formula Kw = [H₃O⁺][OH⁻], if the concentration of hydronium ions ([H₃O⁺]) increases, the concentration of hydroxide ions ([OH⁻]) must decrease to maintain the constant Kw.