Write the formula of each of the following compounds.

(a) Sodium aquapentacyanocobaltate(III)

(b) Dichlorobis(ethylenediamine)chromium(III) nitrate

(c) Triamminetrichlorocobalt(III)

(d) Ammonium diaquadioxalatoferrate(II)

Strategy Use the charge of each ligand, the number of ligands in the complex, and the given oxidation state of the metal to determine the overall charge of the complex. Write the formula of the complex, using the symbol of the metal followed by the formulas of each ligand, using subscripts to show the number of ligands present. Positively charged counterions precede the complex in the formula and negative counterions follow it.