Q28 / 225 · JEE Main 2002 · Chemistry

How do we differentiate between $\mathrm{Fe}^{3+}$ and $\mathrm{Cr}^{3+}$ in group III?

  • A
    by taking excess of $\mathrm{NH}_4 \mathrm{OH}$ solution
  • B
    by increasing $\mathrm{NH}_4{ }^{+}$ion concentration
  • C
    by decreasing $\mathrm{OH}^{-}$ion concentration
  • Correct answer
    D
    both (b) and (c)

Solution

$\mathrm{NH}_4^{+}$ions are increased to suppress release of $\mathrm{OH}$ ions, hence solubility product of $\mathrm{Fe}(\mathrm{OH})_3$ is attained. Colour of precipitate is different.

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

Relevant Questions