One method of analysing the manganese content of steel is to dissolve the steel in nitric acid; producing a solution of manganese(II) ions, Mn²⁺(aq).
The Mn²⁺((aq) ions are then treated with an excess of acidified solution of periodate ions, IO₄^-(aq). The products of this reaction are iodate ions, IO₃^- (aq), and the deeply purple-coloured permanganate ions, MnO₄^- (aq).
The concentration of MnO₄^- (aq) is then determined by UV-visible spectroscopy.
Calculate the oxidation number of iodine in the IO₄^-(aq) ion.
Solution

Give a half equation for the conversion of IO₄^-(aq) into IO₃^- (aq) in acid solution.
Solution.

Is the IO₄^-(aq) ion acting as an oxidant or reductant? Explain your choice.
Solution

An experiment was carried out to determine the percentage of manganese in a particular sample of steel by the above method.
A 13.936 g sample of steel was dissolved in acid and the manganese was converted to MnO₄^-(aq) ions.
The solution containing the MnO₄^-(aq) ions was fi ltered and made up to a volume of 1.00 L.
25.00 mL of this solution was then further diluted to 100.0 mL in a volumetric fl ask. The absorbance, at 525 nm,
of this solution was 0.70.
Next, the absorbance, at 525 nm, of a series of solutions of MnO₄^-(aq) ions of known concentration was measured and a calibration graph drawn.

What is the concentration, in mg L^–1, of MnO₄^-(aq) in the diluted solution in the 100 mL volumetric flask?
Solution

Calculate the mass, in mg, of manganese in the steel sample.
Solution

Calculate the percentage, by mass, of manganese in the steel sample.
Solution