Question

Give formulas for the following.

a. hexakis(pyridine)cobalt (III) chloride

b. pentaammineiodochromium (III) iodide

c. tris(ethylenediamine)nickel (II) bromide

d. potassium tetracyano nickelate (II)

e. tetraaminedichloroplatinum (II) tetra chloroplatinate (II)

Short answer

The formulas are as follows

$$\begin{gathered} \mathrm{a}.\left[\mathrm{Co}\left({\mathrm{C}}_5{\mathrm{H}}_5{\mathrm{N}}_6\right)\right]{\mathrm{Cl}}_3 \\ \mathrm{b}.\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_5\left(\mathrm{I}\right)\right]{\mathrm{I}}_2 \\ \mathrm{c}.\left[\mathrm{Ni}{\left({\mathrm{NH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{NH}}_2\right)}_3\right]{\mathrm{Br}}_2 \\ \mathrm{d}.{\mathrm{K}}_2\left[\mathrm{Ni}{\left(\mathrm{CN}\right)}_4\right] \\ \mathrm{e}.\left[\mathrm{Pt}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]\left[{\mathrm{PtCl}}_4\right] \end{gathered}$$

Step-by-step solution

Formula for part (a)

The metal is a cation complex ion since there is no suffix for metal. The prefix hexakis is used for complicated pyridine ligand and the positive charge (3+) of cation complex is balanced by three chlorine ions (3-). Hence the formula for hexakis(pyridine)cobalt (III) chloride is$\left[\mathrm{Co}\left({\mathrm{C}}_5{\mathrm{H}}_5{\mathrm{N}}_6\right)\right]{\mathrm{Cl}}_3$

Formula for part (b)

The metal is a cation complex ion. The positive charge (2+) of cation complex is balanced by two iodine ions (2-). Hence the formula for pentaammineiodochromium (III) iodide is$\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_5\left(\mathrm{I}\right)\right]{\mathrm{I}}_2$

Formula for part (c)

The metal ion is in a cation complex ion. The positive charge (2+) of cation complex is balanced by two bromide ions (2-). The prefix tris is used for complicated ethylene diammine ligand. Hence the formula for tris(ethylenediamine)nickel (II) bromide is $\left[\mathrm{Ni}{\left({\mathrm{NH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{NH}}_2\right)}_3\right]{\mathrm{Br}}_2$

Formula for part (d)

The metal ion is an anion complex ion as the suffix -ate is used. The negative charge (2-) of anion complex is balanced by two potassium ions(2+). Hence the formula for potassium tetracyano nickelate (II) is ${\mathrm{K}}_2\left[\mathrm{Ni}{\left(\mathrm{CN}\right)}_4\right]$

Formula for part (e)

The metal ion is in both cation and anion complex ions. The positive charge (2+) on cation complex is balanced by negative charge (2-) of the anion complex. The suffix -ate is also present indicating anion complex ion. Hence the formula for tetraaminedichloroplatinum (II) tetra chloroplatinate (II) is $\left[\mathrm{Pt}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]\left[{\mathrm{PtCl}}_4\right]$