Problem 23
Write down formulae for the following ions: (a) manganate(VII); (b) manganate(VI); (c) dichromate(VI); (d) vanadyl; (e) vanadate (ortho and meta); (f) hexacyanoferrate(III). Give an alternative name for manganate(VII).
Problem 24
Give a brief account of the variation in properties of binary oxides of the first row \(d\) -block metals on going from Sc to Zn.
Problem 26
When iron(II) oxalate (oxalate \(=\mathrm{ox}^{2-}\) ) is treated with \(\mathrm{H}_{2} \mathrm{O}_{2}, \mathrm{H}_{2} \mathrm{ox}\) and \(\mathrm{K}_{2}\) ox, a green compound \(\mathrm{X}\) is obtained. \(\mathbf{X}\) reacts with aqueous \(\mathrm{NaOH}\) to give hydrated \(\mathrm{Fe}_{2} \mathrm{O}_{3},\) and is decomposed by light with production of iron(II) oxalate, \(\mathrm{K}_{2}\) ox and \(\mathrm{CO}_{2}\). Analysis of \(\mathrm{X}\) shows it contains \(11.4 \%\) Fe and \(53.7 \%\) ox \(^{2-}\). Deduce the formula of \(\mathbf{x}\) and write equations for its reaction with alkali and its photochemical decomposition. State, with reasons, whether you would expect \(\mathbf{X}\) to be chiral
Problem 27
Dimethyl sulfoxide (DMSO) reacts with cobalt(II) perchlorate in EtOH to give a pink compound A which is a 1: 2 electrolyte and has a magnetic moment of \(4.9 \mu_{\mathrm{B}}\) Cobalt(II) chloride also reacts with DMSO, but in this case the dark blue product, \(\mathbf{B}\), is a 1: 1 electrolyte, and the magnetic moment of \(\mathbf{B}\) is \(4.6 \mu_{\mathrm{B}}\) per Co centre. Suggest a formula and structure for A and B.
Problem 28
When \(\mathrm{H}_{2} \mathrm{S}\) is passed into a solution of copper(II) sulfate acidified with \(\mathrm{H}_{2} \mathrm{SO}_{4},\) copper(II) sulfide precipitates. When concentrated \(\mathrm{H}_{2} \mathrm{SO}_{4}\) is heated with metallic \(\mathrm{Cu}\), the principal sulfur-containing product is \(\mathrm{SO}_{2}\), but a residue of copper(II) sulfide is also formed. Account for these reactions.
Problem 30
(a) The value of \(\mu_{\mathrm{eff}}\) for \(\left[\mathrm{CoF}_{6}\right]^{3-}\) is \(5.63 \mu_{\mathrm{B}} .\) Explain why this value does not agree with the value for \(\mu\) calculated from the spin-only formula. (b) By using a simple \(\mathrm{M} \mathrm{O}\) approach, rationalize why oneelectron oxidation of the bridging ligand in \(\left[(\mathrm{CN})_{5} \mathrm{CoOOCo}(\mathrm{CN})_{5}\right]^{6-}\) leads to a shortening of the \(\mathrm{O}-\mathrm{O}\) bond (c) Salts of which of the following complex ions might be expected to be formed as racemates: \(\left[\mathrm{Ni}(\operatorname{acac})_{3}\right]^{-}\) \(\left[\mathrm{CoCl}_{3}(\mathrm{NCMe})\right]^{-},\) cis-\(\left[\mathrm{Co}(\mathrm{en})_{2} \mathrm{Cl}_{2}\right]^{+},\) trans- \(\left[\mathrm{Cr}(\mathrm{en})_{2} \mathrm{Cl}_{2}\right]^{+} ?\)
