Question

which is a possible example of species that can comprise a buffer solution?
select the correct answer below:
○ hclo₄ and clo₄⁻
○ h₂so₄ and h₂o
○ h₂po₄⁻ and h₃po₄
○ ch₃oh and ch₃cooh

Explanation:

Step1: Recall buffer solution requirements

A buffer solution consists of a weak acid and its conjugate base (or a weak base and its conjugate acid).

Step2: Analyze each option

• Option A: \( \ce{HClO4} \) is a strong acid. Its conjugate base \( \ce{ClO^−4} \) cannot form a buffer with \( \ce{HClO4} \) as strong - acid/conjugate - base pairs do not act as buffers.
• Option B: \( \ce{H2SO4} \) is a strong acid. \( \ce{H2O} \) is not its conjugate base in the context of buffering (and strong acid - water mixtures are not buffers).
• Option C: \( \ce{H3PO4} \) is a weak acid (\( K_{a1}=7.5\times10^{ - 3}\)). \( \ce{H2PO^−4} \) is its conjugate base (\( \ce{H3PO4

ightleftharpoons H^+ + H2PO^−4} \)). This pair (weak acid - conjugate base) can act as a buffer.

• Option D: \( \ce{CH3OH} \) (methanol) is an alcohol (not a base in the acid - base buffering sense). \( \ce{CH3COOH} \) (acetic acid) is a weak acid, but there is no conjugate - base/weak - acid relationship between them for buffering.

Answer:

C. \( \ce{H2PO^−4} \) and \( \ce{H3PO4} \)