19.1 Occurrence, Preparation, and Properties of Transition Metals and Their Compounds

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 $\left[\text{Co} \left(\text{H}_{2} \text{O}\right)_{6}\right]^{3+} \left(a q\right) + \text{e}^{-} \rightarrow \left[\left(\text{Co} \left(\right. \text{H}\right)_{2} \text{O} \left.\right)_{6}\right]^{2+} \left(a q\right)$ is about 1.8 V. The reduction potential for the reaction $\left[\text{Co} \left(\text{NH}_{3}\right)_{6}\right]^{3+} \left(a q\right) + \text{e}^{-} \rightarrow \left[\text{Co} \left(\text{NH}_{3}\right)_{6}\right]^{2+} \left(a q\right)$ 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) $\text{Fe} \left(s\right) + \text{H}_{2} \text{SO}_{4} \left(a q\right) \rightarrow$

(b) $\text{FeCl}_{3} \left(a q\right) + \text{NaOH} \left(a q\right) \rightarrow$

(c) $\text{Mn} \left(\text{OH}\right)_{2} \left(s\right) + \text{HBr} \left(a q\right) \rightarrow$

(d) $\text{Cr} \left(s\right) + \text{O}_{2} \left(g\right) \rightarrow$

(e) $\text{Mn}_{2} \text{O}_{3} \left(s\right) + \text{HCl} \left(a q\right) \rightarrow$

(f) $\text{Ti} \left(s\right) + x s \text{F}_{2} \left(g\right) \rightarrow$

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 $\text{Cr}_{2} \text{O}_{7} ^{2−}$ in hydrochloric acid.

(c) Cr²⁺ is added to $\text{Cr}_{2} \text{O}_{7} ^{2−}$ 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…

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