(i) Describe the type of hybridisation for the complex ion [Fe(H₂O)₆]²+.
(ii) Write the IUPAC name of the ionisation isomer of the coordination compound [Co(NH₃)₅Br]SO₄. Give one chemical test to distinguish between the two compounds.

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(i)$$\begin{gathered} \mathrm{Valence} \mathrm{shell} \mathrm{electronic} \mathrm{configuration} \mathrm{of} \mathrm{Fe} =3{\mathrm{d}}^{6}4{\mathrm{s}}^2 4{\mathrm{p}}^0 4{\mathrm{d}}^0 \\ \mathrm{Fe} \mathrm{in} +2 \mathrm{oxidation} \mathrm{state} \mathrm{in} \left[\mathrm{Fe}\right({\mathrm{H}}_2\mathrm{O}{)}_6{]}^{2+} = 3{\mathrm{d}}^{6 }4{\mathrm{s}}^0 4{\mathrm{p}}^0 4{\mathrm{d}}^0 \\ \mathrm{Now} {\mathrm{H}}_2\mathrm{O} \mathrm{is} \mathrm{a} \mathrm{weak} \mathrm{field} \mathrm{ligand}, \mathrm{so} \mathrm{pairing} \mathrm{does} \mathrm{not} \mathrm{occur} \mathrm{and} \mathrm{the} 6 \mathrm{lone} \mathrm{pair} \mathrm{of} \mathrm{electrons} \mathrm{one} \mathrm{from} \mathrm{each} {\mathrm{H}}_2\mathrm{O} \mathrm{goes} \mathrm{to} 1 4\mathrm{s}, 3 4\mathrm{p} \mathrm{and} 2 4\mathrm{d} \mathrm{orbitals} \mathrm{giving} \mathrm{the} \mathrm{hybridisation} {\mathrm{sp}}^3{\mathrm{d}}^2 \end{gathered}$$
(ii) The coordination isomer of [Co(NH₃)₅Br]SO₄ is [Co(NH₃)₅SO₄]Br whose IUPAC name is Cobalt(III) pentaamminesulphato bromide.
The two can be distinguished by treatment with AgNO₃. [Co(NH₃)₅SO₄]Br​ with AgNO3 gives a pale yellow ppt of AgBr insoluble in HCl. This test is not given by [Co(NH₃)₅Br]SO₄