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Chapter 23: Problem 13

Give the oxidation numbers of the metals in the following species: (a) \(\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right],\) (b) \(\mathrm{K}_{3}\left[\mathrm{Cr}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]\) (c) \(\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}\)

Short Answer

Expert verified
The oxidation numbers of the metals in (a) \(\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]\) is +3, in (b) \(\mathrm{K}_{3}\left[\mathrm{Cr}\left(\mathrm{C}_{2}\mathrm{O}_{4}\right)_{3}\right]\) is +3, in (c) \(\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}\) is +2.

Step by step solution

01

- Assign oxidation states

Assign oxidation states to each atom. The oxidation state (number) of an atom in a substance represents the number of electrons that an atom loses, gains, or appears to use when forming chemical compounds or ions. By convention: \n1. The oxidation state of a pure element is always zero. \n2. For ions, the oxidation state is equal to the charge of the ion. \n3. Hydrogen generally has an oxidation state of +1, oxygen -2 and halogens -1. For those compounds where these elements exhibit other oxidation states, we will use the known oxidation states of the other atoms to work out what those are.
02

- Calculate oxidation number for (a) \(\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]\)

The potassium (\(K\)) ions each have a charge of +1. The complex anion as a whole must have a charge of -3 to balance the +3 charge from the potassium ions. In the complex anion \([\mathrm{Fe}(\mathrm{CN})_{6}]\), the cyanide ion (\(CN^{-}\)) has a total charge of -1. Since there are six cyanide ions, the total negative charge is -6. Therefore, the Iron (\(Fe\)) must have an oxidation number of +3 to balance it out.
03

- Calculate oxidation number for (b) \(\mathrm{K}_{3}\left[\mathrm{Cr}\left(\mathrm{C}_{2}\mathrm{O}_{4}\right)_{3}\right]\)

The potassium (\(K\)) ions each have a charge of +1. The complex anion as a whole must have a charge of -3 to balance the +3 charge from the potassium ions. In the complex anion \(\left[\mathrm{Cr}\left(\mathrm{C}_{2}\mathrm{O}_{4}\right)_{3}\right]\), the oxalate ion (\(C_{2}O_{4}^{2-}\)) has a total charge of -2. Since there are three oxalate ions, the total negative charge is -6. Therefore, the Chromium (\(Cr\)) must have an oxidation number of +3 to balance it out.
04

- Calculate oxidation number for (c) \(\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}\)

In the complex anion \(\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}\), the cyanide ion (\(CN^{-}\)) has a total charge of -1. Since there are four cyanide ions, the total negative charge is -4. Therefore, the Nickel (\(Ni\)) must have an oxidation number of +2 to balance it out.

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Most popular questions from this chapter

Aqueous copper(II) sulfate solution is blue in color. When aqueous potassium fluoride is added, a green precipitate is formed. When aqueous potassium chloride is added instead, a bright-green solution is formed. Explain what is happening in these two cases.

For the same type of ligands, explain why the crystal field splitting for an octahedral complex is always greater than that for a tetrahedral complex.

Predict the number of unpaired electrons in the following complex ions: (a) \(\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{4-},(\mathrm{b})\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\)

Without referring to the text, write the ground-state electron configurations of the first-row transition metals. Explain any irregularities.

Why is zinc not considered a transition metal?
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