Apentix/AP Chemistry/Unit 8: Acids and Bases/Question
AP Chemistrymediummcq1 pt

Solid NaA is dissolved in a solution of weak acid HA. What happens to [H⁺]?

A.It increases because extra A⁻ releases H⁺
B.It decreases because added A⁻ shifts the ionization equilibrium toward HA
C.It is unchanged because solids never affect equilibria
D.It drops to zero because the acid is consumed

Explanation

Core Concept

Adding the conjugate base raises [A⁻], so by Le Chatelier's principle the HA ⇌ H⁺ + A⁻ equilibrium shifts left toward HA. The shared ion suppresses further ionization, lowering [H⁺]. This common-ion effect is precisely why HA mixed with A⁻ produces a working buffer.

Correct Answer

BIt decreases because added A⁻ shifts the ionization equilibrium toward HA

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