SSCE VCE Chemistry Instrumental Analysis of Organic Compounds: One method of analysing the mang

Question

One method of analysing the manganese content of steel is to dissolve the steel in nitric acid; producing a solution of manganese(II) ions, Mn$^{2+}$ (aq).

The Mn$^{2+}$ (aq) ions are then treated with an excess of acidified solution of periodate ions, IO$_4^{-}$ (aq). The products of this reaction are iodate ions, IO$^{-}$ (aq), and the deeply purple-coloured permanganate ions, MnO$_4^{-}$ (aq).

The concentration of MnO$_4^{-}$ (aq) is then determined by UV-visible spectroscopy.

a. 
i.

Give a half equation for the conversion of IO$^{-}$ (aq) into IO$_{3}^{-}$ (aq) in acid solution.

ii.

Is the IO$^{-}$ (aq) ion acting as an oxidant or reductant? Explain your choice.

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 MnO$_4^{-}$ ions.

The solution containing the MnO$_4^{-}$ ions was filtered 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 flask. The absorbance, at 525 nm, of this solution was 0.70.

Next, the absorbance, at 525 nm, of a series of solutions of MnO$_4^{-}$ ions of known concentration was measured and a calibration graph drawn.

One method of analysing the manganese content of steel is to dissolve the steel in nitric acid; producing a solution of manganese(II) ions, Mn$^{2+}$ (aq) - VCE - SSCE Chemistry - Question 2 - 2008 - Paper 1

Worked Solution & Example Answer:One method of analysing the manganese content of steel is to dissolve the steel in nitric acid; producing a solution of manganese(II) ions, Mn$^{2+}$ (aq) - VCE - SSCE Chemistry - Question 2 - 2008 - Paper 1

i. Give a half equation for the conversion of IO$^{-}$ (aq) into IO$_{3}^{-}$ (aq) in acid solution.

ii. Is the IO$^{-}$ (aq) ion acting as an oxidant or reductant? Explain your choice.

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