Q27 / 170 · Manipal (MET) 2021 · Chemistry

The reagent $\mathrm{NH}_4 \mathrm{Cl}$ and aqueous $\mathrm{NH}_3$ will precipitate :

  • A
    $\mathrm{Ca}^{2+}$
  • Correct answer
    B
    $\mathrm{Al}^{3+}$
  • C
    $\mathrm{Mg}^{2+}$
  • D
    $\mathrm{Zn}^{2+}$

Solution

$\mathrm{NH}_4 \mathrm{Cl}$ and aqueous $\mathrm{NH}_3\left(\mathrm{NH}_4 \mathrm{OH}\right)$ precipitates basic radicals of 3rd group of qualitative analysis hydroxides of this group have very low value of solubility product. So, this reagent will precipitate $\mathrm{Al}^{3+}$ because the radicals present in 3rd group are $\mathrm{Al}^{3+}, \mathrm{Cr}^{3+}$, and $\mathrm{Fe}^{3+}$.

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

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