Q39 / 155 · WBJEE 2019 · Chemistry

Which of the following chemicals may be used to identify three unlabelled beakers containing conc.NaOH, conc.$\mathrm{H}_{2}\mathrm{SO}_{4}$ and water?

  • Correct answer
    A
    $\mathrm{NH}_{4} \mathrm{NO}_{3}$
  • B
    $\mathrm{NaCl}$
  • Correct answer
    C
    $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}$
  • D
    HCOONa

Solution

$\mathrm{NH}_{4} \mathrm{NO}_{3}$ will evolve $\mathrm{NH}_{3}$ pungent smelling gas with $\mathrm{NaOH}$. - $\mathrm{NO}_{2}$ brown gas with $\operatorname{con} . \mathrm{H}_{2} \mathrm{SO}_{4}$ - No reaction with water Thus, $\mathrm{NH}_{4} \mathrm{NO}_{3}$ can be used to label all three beakers. (c) $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}$ will evolve pungent smelling gas $\mathrm{NH}_{3}$ with $\mathrm{NaOH}$ - Effervescence of $\mathrm{CO}_{2}$ gas with con. $\mathrm{H}_{2} \mathrm{SO}_{4}$ - No reaction with water. Thus, $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}$ can be used to label all three beakers. Thus, options $(a, c)$ are correct.

Hence, the correct answer is options: 'A', 'C'.

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