IIT-JEE 2010 · Paper 1 · Chemistry Q13

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ChemistryMultiple correct+3Question 13 of 84

Aqueous solutions of $\ce{HNO3}$ , KOH, $\ce{CH3COOH}$ , and $\ce{CH3COONa}$ of identical concentrations are provided. The pair(s) of solutions which form a buffer upon mixing is(are)

\ce{HNO3}

and

\ce{CH3COOH}

KOH and

\ce{CH3COONa}

\ce{HNO3}

and

\ce{CH3COONa}

\ce{CH3COOH}

and

\ce{CH3COONa}

Answer and worked solution

Official answer: C, D

A buffer needs a weak acid together with its conjugate base (or a weak base with its conjugate acid).

(A) A strong acid and a weak acid: no conjugate base. No.
(B) A strong base and a weak base: no.
(C) $\ce{HNO3 + CH3COONa -> CH3COOH + NaNO3}$ ; with acetate in excess (e.g. less acid than salt), the mixture contains $\ce{CH3COOH}$ and $\ce{CH3COO-}$ . Yes.
(D) Acetic acid with sodium acetate: the classic acidic buffer. Yes.

(C), (D)

Topics:Buffer solutions

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IIT-JEE 2010 · Paper 1, Chemistry question 13