Question

Write the formula of the following coordination compounds:
(i) Hexa aqua chromium (III) chloride
(ii) Dichlorido diammin e platinum (II)
(iii) Hexa ammine platinum (IV) chloride
(iv) Sodium penta cyano nitrosyl ferrate (II)

Hint:

While writing formulae: put the coordination entity in square brackets, list ligands alphabetically inside the bracket, compute the complex charge from metal oxidation state and ligand charges, then add the appropriate counter-ions outside the bracket.

Answer 1

(i) Hexa aqua chromium(III) chloride $\Rightarrow$ \(\boxed{[\mathrm{Cr(H_2O)_6}]\mathrm{Cl}_3}\)
(Complex cation charge $+3$ balanced by $3$ chloride ions.)
(ii) Dichlorido diammin e platinum(II) $\Rightarrow$ \(\boxed{[\mathrm{Pt(NH_3)_2Cl_2}]}\)
(Neutral complex: Pt$^{2+}$ with two neutral ammine and two chlorido ligands.)
(iii) Hexa ammine platinum(IV) chloride $\Rightarrow$ \(\boxed{[\mathrm{Pt(NH_3)_6}]\mathrm{Cl}_4}\)
(Pt$^{4+}$ with six neutral ammine ligands gives a $4+$ complex cation, balanced by $4$ Cl$^-$.)
(iv) Sodium penta cyano nitrosyl ferrate(II) $\Rightarrow$ \(\boxed{\mathrm{Na_2[Fe(CN)_5NO]}}\)
(Anion charge $-2$ since Fe$^{2+}$, five CN$^-$ and NO$^+$; hence $2$ Na$^+$ counterions.)