Which of the following complexes exhibit(s) magnetic moment close to 2 BM ? $$ \left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]\left(\mathrm{NO}_3\right)_2, \mathrm{~K}_2\left[\mathrm{MnCl}_4\right], \mathrm{K}_4\left[\mathrm{Mn}(\mathrm{CN})_6\right] \text {, and }\left[\mathrm{Ni}(\mathrm{CO})_4\right] $$

The following complex ions absorb in the ultraviolet-visible region of light. Which one of these shows violet colour?

$$ \left[\mathrm{CoCl}\left(\mathrm{NH}_3\right)_5\right]^{2+},\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)\left(\mathrm{NH}_3\right)_5\right]^{3+},\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}, \text { and }\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-} $$

The products of the reaction between aqueous solutions of $K_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]$ and $\frac{1}{2} \mathrm{H}_2 \mathrm{O}_2$ are

For the colourless complex $\left[M\left(H_2 O\right)_6\right]^{n+}$, where $M$ is a $3 d$ transition metal, the CORRECT ground state $d$-electron configuration of $M$ is