0.001 mole of [Co (NH_3)_5 (NO_3)(SO_4)] was passed through a...

0.001 mole of

\left[\mathrm{Co}

\left(\mathrm{NH}_3\right)_5

\left(\mathrm{NO}_3\right)\left(\mathrm{SO}_4\right)\right]

was passed through a cation exchanger and the acid coming out of it required 20 mL of 0.1 M NaOH for neutralisation. Thus, the complex is

Options

A $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{NO}_3\right)\right] \mathrm{SO}_4$
B $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{SO}_4\right)\right] \mathrm{NO}_3$
C $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\right] \mathrm{NO}_3 \cdot \mathrm{SO}_4$
DNone of the above

A. $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{NO}_3\right)\right] \mathrm{SO}_4$

Millimoles of acid required for neutralisation

\begin{aligned} & =20 \times 0.1=2 \text{ millimoles } \\ & =0.002 \text{ moles }\end{aligned}

If 0.001 mole is neutralising 0.002 moles of base, thus, 0.001 mole of base remains unreacted. Hence, acid coming out should be basic.

\begin{aligned} & {\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{NO}_3\right)\right] \mathrm{SO}_4 \longrightarrow} \\ & {\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{NO}_3\right]^{2+}+\mathrm{SO}_4^{2-}\right.}\end{aligned}