Q17 / 155 · WBJEE 2021 · Chemistry
A solution is made by a concentrated solution of $\mathrm{Co}\left(\mathrm{NO}_{3}\right)_{2}$ with a concentrated solution of $\mathrm{NaNO}_{2}$ in $50 \%$ acetic acid. A solution of a salt containing metal $\mathrm{M}$ is added to the mixture, when a yellow precipitate is formed. Metal ' $\mathrm{M}$ ' is
- AMagnesium
- BSodium
- Correct answerCPotassium
- DZinc
Solution
$\begin{array}{l}
\mathrm{Co}\left(\mathrm{NO}_{3}\right)_{3}+\mathrm{NaNO}_{2} \longrightarrow \mathrm{Na}_{3}\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}\right] \\
\mathrm{Na}_{3}\left[\mathrm{Co}\left(\mathrm{NO}_{3}\right)_{6}\right]+\mathrm{K}^{+} \longrightarrow \mathrm{K}_{3}\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}\right] \downarrow \text { yellow ppt }
\end{array}$
Hence, the correct answer is option: 'C'.