Q77 / 160 · JIPMER 2012 · Chemistry

Which buffer solution comprising of the following has its pH value greater than 7 ?

  • A
    $\mathrm{CH}_3 \mathrm{COOH}+\mathrm{CH}_3 \mathrm{COONa}$
  • B
    $\mathrm{HCOOH}+\mathrm{HCOOK}$
  • C
    $\mathrm{CH}_3 \mathrm{COONH}_4$
  • Correct answer
    D
    $\mathrm{NH}_4 \mathrm{OH}+\mathrm{NH}_4 \mathrm{Cl}$

Solution

The pH value of basic buffer solutions is always greater than 7. Among the given, only $\mathrm{NH}_4 \mathrm{OH}+\mathrm{NH}_4 \mathrm{Cl}$ constitutes the basic buffer (a mixture of weak base and its conjugated salt), thus, has pH greater than 7 .

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

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