Aqueous solutions of $\mathrm{HNO}_{3}, \mathrm{KOH}, \mathrm{CH}_{3} \mathrm{COOH}$, and $\mathrm{CH}_{3} \mathrm{COONa}$ of identical concentrations are provided. The pair(s) of solutions which form a buffer upon mixing is(are)

(C) $\mathrm{HNO}_{3}$ and $\mathrm{CH}_{3} \mathrm{COONa}$; (D) $\mathrm{CH}_{3} \mathrm{COOH}$ and $\mathrm{CH}_{3} \mathrm{COONa}$

(A) $\mathrm{HNO}_{3}$ and $\mathrm{CH}_{3} \mathrm{COOH}$

(B) KOH and $\mathrm{CH}_{3} \mathrm{COONa}$

JEE Advanced · 2010 · 11 Apr 2010 · Paper 1 · Equilibrium

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Aqueous solutions of

HNO_{3}, KOH, CH_{3} COOH

, and

CH_{3} COONa

of identical concentrations are provided. The pair(s) of solutions which form a buffer upon mixing is(are)

(A) $HNO_{3}$ and $CH_{3} COOH$
(B)KOH and $CH_{3} COONa$
(C) $HNO_{3}$ and $CH_{3} COONa$ ✓ Correct
(D) $CH_{3} COOH$ and $CH_{3} COONa$ ✓ Correct

Answer: (C), (D)

Solution

A buffer is formed by a weak acid and its conjugate base (salt with strong base), or by mixing a strong acid with a weak acid's salt in limiting amount.

Option (C): If

HNO_{3}

(strong acid) is present in limiting amount, it will partially neutralize

CH_{3} COONa

to produce

CH_{3} COOH

, creating a buffer of weak acid and its salt.

Option (D): This mixture directly contains a weak acid

CH_{3} COOH

and its salt

CH_{3} COONa

, which is the classic acidic buffer system.

Options (A) and (B) do not form buffers as they lack the weak acid-conjugate base pair.

JEE Advanced · 2010 · 11 Apr 2010 · Paper 1 · One or more correct options

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JEE Advanced · 2010 · 11 Apr 2010 · Paper 1 · Equilibrium

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