Problem 23 - Chemistry Central Science

Question

Write the formula for each of the following compounds, being sure to use brackets to indicate the coordination sphere: (a) hexaamminechromium(III) nitrate (b) tetraamminecarbonatocobalt(III) sulfate (c) dichlorobis(ethylenediamine)platinum(IV) bromide (d) potassium diaquatetrabromovanadate(III) (e) bis(ethylenediamine) zinc(II) tetraiodomercurate(II)

Step-by-Step Solution

Answer

The short versions of the chemical formulas for the given coordination compounds are as follows: (a) hexaamminechromium(III) nitrate: \([Cr(NH_3)_6](NO_3)_3\) (b) tetraamminecarbonatocobalt(III) sulfate: \([Co(NH_3)_4CO_3](SO_4)\) (c) dichlorobis(ethylenediamine)platinum(IV) bromide: \([PtCl_2(en)_2](Br)_2\) (d) potassium diaquatetrabromovanadate(III): \(K[V(OH_2)_2Br_4]\) (e) bis(ethylenediamine) zinc(II) tetraiodomercurate(II): \([Zn(en)_2](HgI_4)\)

Step 1: Identify the central atom and counter ion

The central atom of this coordination complex is chromium (Cr). The compound is hexaamminechromium(III), which means that Cr has an oxidation state of 3. The counter ion is nitrate (NO₃⁻).

Step 2: Write the formula for the coordination sphere

There are six ammine ligands (NH₃) and one chromium(III), so the coordination sphere is [Cr(NH₃)₆]³⁺.

Step 3: Balance the overall charge with counter ions

Since the charge of the coordination sphere is +3, we need three nitrate anions for a neutral compound. So, the formula of hexaamminechromium(III) nitrate is [Cr(NH₃)₆](NO₃)₃. (b) tetraamminecarbonatocobalt(III) sulfate

Step 1: Identify the central atom and counter ion

The central atom is cobalt (Co) in the +3 oxidation state. The counter ion is sulfate (SO₄²⁻).

Step 2: Write the formula for the coordination sphere

The complex has four ammine ligands (NH₃) and one carbonate ligand (CO₃²⁻). The coordination sphere is [Co(NH₃)₄CO₃]⁺.

Step 3: Balance the overall charge with counter ions

Since the charge of the coordination sphere is +1, we need one sulfate anion to form a neutral compound. The formula for tetraamminecarbonatocobalt(III) sulfate is [Co(NH₃)₄CO₃](SO₄). (c) dichlorobis(ethylenediamine)platinum(IV) bromide

Step 1: Identify the central atom and counter ion

The central atom is platinum (Pt) in the +4 oxidation state. The counter ion is bromide (Br⁻).

Step 2: Write the formula for the coordination sphere

The complex has two chloro ligands (Cl⁻) and two ethylenediamine ligands (en). The coordination sphere is [PtCl₂(en)₂]²⁺.

Step 3: Balance the overall charge with counter ions

Since the charge of the coordination sphere is +2, we need two bromide anions to form a neutral compound. The formula for dichlorobis(ethylenediamine)platinum(IV) bromide is [PtCl₂(en)₂](Br)₂. (d) potassium diaquatetrabromovanadate(III)

Step 1: Identify the central atom and counter ion

The central atom is vanadium (V) in the +3 oxidation state. The counter ion is potassium (K⁺).

Step 2: Write the formula for the coordination sphere

The complex has two aqua ligands (H₂O) and four bromo ligands (Br⁻). The coordination sphere is [V(OH₂)₂Br₄]⁻.

Step 3: Balance the overall charge with counter ions

Since the charge of the coordination sphere is -1, we need one potassium cation to form a neutral compound. The formula for potassium diaquatetrabromovanadate(III) is K[V(OH₂)₂Br₄]. (e) bis(ethylenediamine) zinc(II) tetraiodomercurate(II)

Step 1: Identify the central atom and counter ion

The central atom is zinc (Zn) in the +2 oxidation state. The counter ion is tetraiodomercurate(II), which is HgI₄²⁻.

Step 2: Write the formula for the coordination sphere

The complex has two ethylenediamine ligands (en). The coordination sphere is [Zn(en)₂]²⁺.

Step 3: Balance the overall charge with counter ions

Since the charge of the coordination sphere is +2, we need one tetraiodomercurate(II) anion to form a neutral compound. The formula for bis(ethylenediamine) zinc(II) tetraiodomercurate(II) is [Zn(en)₂](HgI₄).