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Basic Buffer Action

A physician w...

Question

A physician wishes to prepare a buffer solution at pH = 3.58 that efficiently resists a change in pH yet contains only small conc. of the buffering acid. Which one of the following weak acid together with its sodium salt, would be best to use.

m - chloro benzoic acid

(p K_{a} = 3.98)

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p - chloro cinnamic acid

(p K_{a} = 4.41)

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2,5 - dihydroxy benzoic acid

(p K_{a} = 2.97)

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Acetoacetic acid

(p K_{a} = 3.58)

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Solution

The correct option is D Acetoacetic acid $(p K_{a} = 3.58)$
The expression for the pH of the acidic buffer solution is as given below.
$p H = p K_{a} + l o g \frac{[s a l t]}{[a c i d]}$
For option (D), $p H = 3.58$ , $p K_{a} = 2.58$ .
Substitute values in the above equation.
$3.58 = 3.58 + l o g \frac{[s a l t]}{[a c i d]}$ .
Hence, $[s a l t] : [a c i d] = 1 : 1$ .

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Similar questions

A physician wishes to prepare a buffer solution at pH = 3.58 that efficiently resists a change in pH yet contains only small conc. of the buffering agents. Which one of the following weak acid together with its sodium salt would be best to use?

Q. Buffer capacity of acid buffer solution is more when
A)

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[S a l t] = [A c i d]

P^{K a} = 7

[H +]

P^{K a}

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benzoic acid

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solutions are given separately. What is the volume of benzoic acid required to prepare a

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A physician wishes to prepare a buffer solution at pH = 3.58 that efficiently resists a change in pH yet contains only small conc. of the buffering acid. Which one of the following weak acid together with its sodium salt, would be best to use.

The correct option is D Acetoacetic acid (pKa=3.58)The expression for the pH of the acidic buffer solution is as given below.pH=pKa+log[salt][acid]For option (D), pH=3.58, pKa=2.58.Substitute values in the above equation.3.58=3.58+log[salt][acid].Hence, [salt]:[acid]=1:1.