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Chapter 21: Problem 34

A coordination compound of cobalt (III) contains four ammonia molecules, one sulfate ion, and one chloride ion. Addition of aqueous \(\mathrm{BaCl}_{2}\) solution to an aqueous solution of the compound gives no precipitate. Addition of aqueous \(\mathrm{AgNO}_{3}\) to an aqueous solution of the compound produces a white precipitate. Propose a structure for this coordination compound.

Short Answer

Expert verified
The structure of the coordination compound is [Co(NH3)4(SO4)]Cl2. The coordination sphere contains the cobalt (III) ion, four ammonia ligands, and a sulfate ion. The chloride ion acts as a counterion outside the coordination sphere. The chemical tests indicate that the sulfate ion is within the coordination sphere, while the chloride ion is acting as a counterion.

Step by step solution

01

List the given information

We know that the coordination compound contains: - Cobalt (III) as the central metal ion - Four ammonia molecules as ligands - One sulfate ion - One chloride ion We also know that when the compound is mixed with: - Aqueous \(\mathrm{BaCl}_{2}\), no precipitate forms - Aqueous \(\mathrm{AgNO}_{3}\), a white precipitate forms
02

Identify the coordination sphere

The coordination sphere contains the central metal ion and its ligands. In this case, the coordination sphere will contain the cobalt (III) ion and four ammonia molecules. The coordination sphere is usually written as [Co(NH3)4]
03

Analyze the results of the tests

When the compound is mixed with aqueous \(\mathrm{BaCl}_{2}\), no precipitate forms. This indicates that the sulfate ion is not acting as a counterion, because \(\mathrm{BaSO}_{4}\) is insoluble in water and would form a precipitate if the sulfate ion was acting as a counterion. Thus, the sulfate ion must also be within the coordination sphere. When the compound is mixed with aqueous \(\mathrm{AgNO}_{3}\), a white precipitate forms, which indicates the formation of \(\mathrm{AgCl}\), an insoluble compound in water. Thus, the chloride ion must be acting as a counterion outside the coordination sphere.
04

Propose the structure of the coordination compound

Considering the information obtained from the chemical tests, we conclude that the coordination sphere contains both the ammonia ligands and the sulfate ion. Since the charge of cobalt (III) is +3, the charge of the coordination sphere becomes +2 due to the presence of the sulfate ion with charge -1. The coordination sphere: [Co(NH3)4(SO4)] As the chloride ion acts as a counterion and the coordination sphere has a charge of +2, we will need two chloride ions to balance the overall charge of the complex. The final structure of the coordination compound is: [Co(NH3)4(SO4)]Cl2

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Most popular questions from this chapter

For the process $$\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}^{2+}(a q)+\mathrm{Cl}^{-}(a q) \longrightarrow \mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}^{+}(a q)+\mathrm{NH}_{3}(a q)$$ what would be the expected ratio of cis to trans isomers in the product?

What is the maximum number of unpaired \(d\) electrons that an octahedral transition metal complex ion can have? Predict a compound that would have this number of unpaired electrons.

The ferrate ion, \(\mathrm{FeO}_{4}^{2-}\) , is such a powerful oxidizing agent that in acidic solution, aqueous ammonia is reduced to elemental nitrogen along with the formation of the iron(III) ion. a. What is the oxidation state of iron in FeO \(_{4}^{2-},\) and what is the electron configuration of iron in this polyatomic ion? b. If 25.0 \(\mathrm{mL}\) of a 0.243 \(\mathrm{M} \mathrm{FeO}_{4}^{2-}\) solution is allowed to react with 55.0 \(\mathrm{mL}\) of 1.45 \(\mathrm{M}\) aqueous ammonia, what volume of nitrogen gas can form at $25^{\circ} \mathrm{C}\( and 1.50 \)\mathrm{atm}$ ?

When aqueous KI is added gradually to mercury(II) nitrate, an orange precipitate forms. Continued addition of KI causes the precipitate to dissolve. Write balanced equations to explain these observations. $\left(\text {Hint} : \mathrm{Hg}^{2+} \text { reacts with } \mathrm{I}^{-} \text { to form } \mathrm{HgI}_{4}^{2-} .\right)\( Would you expect \)\mathrm{Hg} \mathrm{I}_{4}^{2-}$ to form colored solutions? Explain.

The compound $\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6} \mathrm{Cl}_{2}$ is green, whereas \(\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6} \mathrm{Cl}_{2}\) is violet. Predict the predominant color of light absorbed by each compound. Which compound absorbs light with the shorter wavelength? Predict in which compound \(\Delta\) is greater and whether \(\mathrm{H}_{2} \mathrm{O}\) or \(\mathrm{NH}_{3}\) is the stronger field ligand. Do your conclusions agree with the spectrochemical series?
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