Q46 / 180 · AIIMS 2003 · Chemistry

Which one of the following is not a buffer solution?

  • A
    $0.8 \mathrm{M} \mathrm{H}_2 \mathrm{~S}+0.8 \mathrm{M} \mathrm{KHS}$
  • B
    $2 \mathrm{M} \mathrm{C}_6 \mathrm{H}_5 \mathrm{NH}_2+2 \mathrm{M} \mathrm{C}_6 \mathrm{H}_5 \mathrm{NH}_3{ }^{+} \mathrm{Br}^{-}$
  • C
    $3 \mathrm{M} \mathrm{H}_2 \mathrm{CO}_3+3 \mathrm{M} \mathrm{KHCO}$
  • Correct answer
    D
    $0.05 \mathrm{M} \mathrm{KClO}_4+0.05 \mathrm{M} \mathrm{HClO}_4$

Solution

Buffer solutions can be obtained by mixing a weak acid with its salt formed with a strong base or by mixing a weak base with its salt formed with a strong acid. As $\mathrm{HClO}_4$ is a strong acid, therefore equimolar mixture of $\mathrm{HClO}_4$ and its salt $\mathrm{KClO}_4$ is not a buffer solution.

Hence, the correct answer is option: 'D'.

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