Q46 / 180 · KCET 2007 · Chemistry

Which one of the following salts on being dissolved in water gives $\mathrm{pH}>7$ at $25^{\circ} \mathrm{C}$ ?

  • Correct answer
    A
    $\mathrm{KCN}$
  • B
    $\mathrm{KNO}_{3}$
  • C
    $\mathrm{NH}_{4} \mathrm{Cl}$
  • D
    $\mathrm{NH}_{4} \mathrm{CN}$

Solution

$\mathrm{KCN}$ is a salt of weak acid and strong base hence, on being dissolved in water it gives basic solution i.e. $\mathrm{pH}>7$ at $25^{\circ} \mathrm{C}$. $$ 2 \mathrm{H}_{2} \mathrm{SO}_{4}+2 \mathrm{P}_{2} \mathrm{O}_{5} \longrightarrow 2 \mathrm{SO}_{3}+\quad 4 \mathrm{HPO}_{3} $$ Sulphur trioxide

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

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