Question

Give the chemical formula of each of the following compounds:

(a) Silver hexacyanoferrate(II)

(b) Potassium tetraisothiocyanatocobaltate(II)

(c) Sodium hexafluorovanadate(III)

(d) Potassium trioxalatochromate(III)

Short answer

$\begin{array}{l}{\text{a)Ag}}_{\text{4}}\left[\text{Fe}{\left(\text{CN}\right)}_{\text{6}}\right]\\ \mathrm{b}){\text{K}}_2\left[\text{Co}{\left(\text{NCS}\right)}_{\text{4}}\right]\\ \mathrm{c}){\text{Na}}_3\left[\text{V}{\left(\text{F}\right)}_{\text{6}}\right]\\ \mathrm{d}){\text{K}}_{\text{3}}\left[\text{Cr}{\left(\text{OX}\right)}_{\text{3}}\right]\end{array}$

Step-by-step solution

Coordination compound

Coordination compounds are “complex molecules” in whichmetal ions (mainly transition metal) are bounded to ligands that can be neutral or possess a negative charge.

a) Chemical formula of silver hexacyanoferrate(II)

In the coordination compound, the silver hexacyanoferrate(III) anion has six cyanide ligand (with -1 charges) are coordinated to the iron atom in +2 oxidation state complex will have overall of -4 charge, four silver cation are required thus the chemical formula of hexacyanoferrate (III) becomes:

${\text{Ag}}_{\text{4}}\left[\text{Fe}{\left(\text{CN}\right)}_{\text{6}}\right]$

b) Chemical formula of potassium tetraisothiocyanatocobaltate(II)

In the coordination compound, the tetraisothiocyanatocobaltate(II),the anion has four thiocyanate ligand (with -1 charges) are coordinated to cobalt atom in +2 oxidation state complex will have overall of -2 charge, two potassium cation are required thus the chemical formula of tetraisothiocyanatocobaltate(II)becomes:

${\text{K}}_2\left[\text{Co}{\left(\text{NCS}\right)}_{\text{4}}\right]$

c) Chemical formula of sodium hexafluorovandate(III)

In the coordination compound, the sodium hexafluorovandate(III),the anion has six fluoride ligand (with -1 charges) are coordinated to vanadium atom in +3 oxidation state complex will have overall of -3 charge, three sodium cation are required thus the chemical formula of sodium hexafluorovandate becomes:

${\text{Na}}_3\left[\text{V}{\left(\text{F}\right)}_{\text{6}}\right]$

d) Chemical formula of potassium trioxalatochromate(III)

In the coordination compound, the potassium trioxolalatochromate(III) the anion has three thiocyanateligand (with -2 charges) are coordinated to chromium atom in +3 oxidation state complex will have overall of -3 charge, three potassium cation are required thus the chemical formula of potassium trioxolalatochromate(III) becomes:

${\text{K}}_{\text{3}}\left[\text{Cr}{\left(\text{OX}\right)}_{\text{3}}\right]$