Exercises

Write the electron configurations for each of the following elements:

(a) Sc

(b) Ti

(c) Cr

(d) Fe

(e) Ru

Write the electron configurations for each of the following elements and its 3+ ions:

(a) La

(b) Sm

(c) Lu

Which of the following elements is most likely to be used to prepare La by the reduction of La₂O₃: Al, C, or Fe? Why?

Which of the following elements is most likely to form an oxide with the formula MO₃: Zr, Nb, or Mo?

Why is the formation of slag useful during the smelting of iron?

Iron(II) can be oxidized to iron(III) by dichromate ion, which is reduced to chromium(III) in acid solution. A 2.5000-g sample of iron ore is dissolved and the iron converted into iron(II). Exactly 19.17 mL of 0.0100 M Na₂Cr₂O₇ is required in the titration. What percentage of the ore sample was iron?

Find the potentials of the following electrochemical cell:

Cd | Cd²⁺, M = 0.10 ‖ Ni²⁺, M = 0.50 | Ni

The standard reduction potential for the reaction ${[\text{Co}{({\text{H}}_2\text{O})}_6]}^{\mathrm{3+}}(aq)+{\text{e}}^{-}⟶{[{\text{Co}(\text{H}}_2\text{O}{)}_6]}^{\mathrm{2+}}(aq)$ is about 1.8 V. The reduction potential for the reaction ${[\text{Co}{({\text{NH}}_3)}_6]}^{\mathrm{3+}}(aq)+{\text{e}}^{-}⟶{[\text{Co}{({\text{NH}}_3)}_6]}^{\mathrm{2+}}(aq)$ is +0.1 V. Calculate the cell potentials to show whether the complex ions, [Co(H₂O)₆]²⁺ and/or [Co(NH₃)₆]²⁺, can be oxidized to the corresponding cobalt(III) complex by oxygen.

Predict the products of each of the following reactions. (Note: In addition to using the information in this chapter, also use the knowledge you have accumulated at this stage of your study, including information on the prediction of reaction products.)

(a) $\text{Fe}(s)+{\text{H}}_2{\text{SO}}_4(aq)⟶$

(b) ${\text{FeCl}}_3(aq)+\text{NaOH}(aq)⟶$

(c) $\text{Mn}{(\text{OH})}_2(s)+\text{HBr}(aq)⟶$

(d) $\text{Cr}(s)+{\text{O}}_2(g)⟶$

(e) ${\text{Mn}}_2{\text{O}}_3(s)+\text{HCl}(aq)⟶$

(f) $\text{Ti}(s)+xs{\text{F}}_2(g)⟶$

Predict the products of the following reactions and balance the equations.

(a) Zn is added to a solution of Cr₂(SO₄)₃ in acid.

(b) FeCl₂ is added to a solution containing an excess of ${\text{Cr}}_2{\text{O}}_7{}^{\mathrm{2-}}$ in hydrochloric acid.

(c) Cr²⁺ is added to ${\text{Cr}}_2{\text{O}}_7{}^{\mathrm{2-}}$ in acid solution.

(d) Mn is heated with CrO₃.

(e) CrO is added to 2HNO₃ in water.

(f) FeCl₃ is added to an aqueous solution of NaOH.

Predict the products of each of the following reactions and then balance the chemical equations.

(a) Fe is heated in an atmosphere of steam.

(b) NaOH is added to a solution of Fe(NO₃)₃.

(c) FeSO₄ is added to an acidic solution of KMnO₄.

(d) Fe is added to a dilute solution of H₂SO₄.

(e) A solution of Fe(NO₃)₂ and HNO₃ is allowed to stand in air.

(f) FeCO₃ is added to a solution of HClO₄.

(g) Fe is heated in air.

Dilute sodium cyanide solution is slowly dripped into a slowly stirred silver nitrate solution. A white precipitate forms temporarily but dissolves as the addition of sodium cyanide continues. Use chemical equations to explain this observation. Silver cyanide is similar to silver chloride in its solubility.

Give the oxidation state of the metal for each of the following oxides of the first transition series. (Hint: Oxides of formula M₃O₄ are examples of mixed valence compounds in which the metal ion is present in more than one oxidation state. It is possible to write these compound formulas in the equivalent format MO·M₂O₃, to permit estimation of the metal’s two oxidation states.)

(a) Sc₂O₃

(b) TiO₂

(c) V₂O₅

(d) CrO₃

(e) MnO₂

(f) Fe₃O₄

(g) Co₃O₄

(h) NiO

(i) Cu₂O

Give the coordination numbers and write the formulas for each of the following, including all isomers where appropriate:

(a) tetrahydroxozincate(II) ion (tetrahedral)

(b) hexacyanopalladate(IV) ion

(c) dichloroaurate(I) ion (note that aurum is Latin for "gold")

(d) diamminedichloroplatinum(II)

(e) potassium diamminetetrachlorochromate(III)

(f) hexaamminecobalt(III) hexacyanochromate(III)

(g) dibromobis(ethylenediamine) cobalt(III) nitrate

Sketch the structures of the following complexes. Indicate any cis, trans, and optical isomers.

(a) [Pt(H₂O)₂Br₂] (square planar)

(b) [Pt(NH₃)(py)(Cl)(Br)] (square planar, py = pyridine, C₅H₅N)

(c) [Zn(NH₃)₃Cl]⁺ (tetrahedral)

(d) [Pt(NH₃)₃Cl]⁺ (square planar)

(e) [Ni(H₂O)₄Cl₂]

(f) [Co(C₂O₄)₂Cl₂]³⁻ (note that ${\text{C}}_2{\text{O}}_4{}^{\mathrm{2-}}$ is the bidentate oxalate ion, $-{\text{O}}_2{\text{CCO}}_2{}^{\text{−}})$

Name each of the compounds or ions given in Exercise 19.28, including the oxidation state of the metal.

Specify whether the following complexes have isomers.

(a) tetrahedral [Ni(CO)₂(Cl)₂]

(b) trigonal bipyramidal [Mn(CO)₄NO]

(c) [Pt(en)₂Cl₂]Cl₂

Draw the geometric, linkage, and ionization isomers for [CoCl₅CN][CN].

Draw the crystal field diagrams for [Fe(NO₂)₆]⁴⁻ and [FeF₆]³⁻. State whether each complex is high spin or low spin, paramagnetic or diamagnetic, and compare Δ_oct to P for each complex.

The solid anhydrous solid CoCl₂ is blue in color. Because it readily absorbs water from the air, it is used as a humidity indicator to monitor if equipment (such as a cell phone) has been exposed to excessive levels of moisture. Predict what product is formed by this reaction, and how many unpaired electrons this complex will have.

How many unpaired electrons are present in each of the following?

(a) [CoF₆]³⁻ (high spin)

(b) [Mn(CN)₆]³⁻ (low spin)

(c) [Mn(CN)₆]⁴⁻ (low spin)

(d) [MnCl₆]⁴⁻ (high spin)

(e) [RhCl₆]³⁻ (low spin)

For complexes of the same metal ion with no change in oxidation number, the stability increases as the number of electrons in the t_2g orbitals increases. Which complex in each of the following pairs of complexes is more stable?

(a) [Fe(H₂O)₆]²⁺ or [Fe(CN)₆]⁴⁻

(b) [Co(NH₃)₆]³⁺ or [CoF₆]³⁻

(c) [Mn(CN)₆]⁴⁻ or [MnCl₆]⁴⁻

Would you expect the complex [Co(en)₃]Cl₃ to have any unpaired electrons? Any isomers?

Would you expect salts of the gold(I) ion, Au⁺, to be colored? Explain.