Which compounds can form a buffer solution when combined in equal molar amounts?

The formation of a buffer solution requires a weak acid and its conjugate base, or a weak base and its conjugate acid. In this context, choosing a combination of compounds that meet these criteria is essential.

In the case of acetic acid (CH3COOH) and sodium acetate (CH3COONa), acetic acid acts as a weak acid, while sodium acetate provides the conjugate base (acetate ion). When these two substances are mixed in equal molar amounts, they create a buffer solution that can resist changes in pH upon the addition of small amounts of strong acid or strong base. This is because the acetic acid can neutralize added bases, while the acetate ions can neutralize added acids.

The other combinations do not fit the criteria for forming a buffer. Hydrochloric acid (HCl) is a strong acid and would not form a buffer with acetic acid since it does not effectively have both components (weak acid and its conjugate base). Similarly, sodium hydroxide (NaOH) is a strong base and would not form a buffer with potassium acetate (CH3COOK) as potassium acetate does not provide a corresponding weak acid. Lastly, sulfuric acid (H2SO4) is