Question

question 6 of 32
which of the following combinations of compounds will make a buffer when mixed?

a. hcl and nabr

b. ch₃cooh and nach₃coo

c. ch₃cooh and nh₄cl

d. hcl and naoh

Explanation:

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

• Option A: HCl is a strong acid, NaBr is a salt of strong acid (HBr) and strong base (NaOH). No weak acid - conjugate base pair.
• Option B: $\ce{CH3COOH}$ (acetic acid, weak acid) and $\ce{NaCH3COO}$ (sodium acetate, which provides $\ce{CH3COO-}$, the conjugate base of $\ce{CH3COOH}$). This is a weak acid - conjugate base pair, so it can form a buffer.
• Option C: $\ce{CH3COOH}$ (weak acid) and $\ce{NH4Cl}$ (salt of weak base $\ce{NH3}$ and strong acid HCl). No conjugate base of $\ce{CH3COOH}$ here.
• Option D: HCl (strong acid) and NaOH (strong base) will neutralize each other, no buffer components.

Answer:

B. $\ce{CH3COOH}$ and $\ce{NaCH3COO}$