Calculate the percentage of iron in the original sample.

An 8.00g sample of iron was extracted from a blast furnace and analysed as follows. The iron was completely dissolved in acid, and the Fe3+ ions produced were the precipitated out of the solution as iron(III) hydroxide, by the addition of ammonia:

Fe3+ (aq) + 3NH3 (aq) + 3H2O (l) à Fe(OH)3 (s) + 3NH4+ (aq)

The precipitate was collected on ash-free filter paper, washed and then transferred to a crucible and heated. This produced iron (III) oxide. The filter paper was completely burnt away in this procedure:

2Fe(OH)3 (s) à Fe2O3 (s) + 3H2O (g)

The mass of iron (III) oxide produced was 10.99g.

Expert Answers

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An 8.00 g sample of iron was extracted from a blast furnace and analyzed as follows. First the iron in the sample was completely dissolved in an acid and the Fe3+ ions precipitated as ferric(III) hydroxide Fe(OH)3 by the addition of ammonia:

Fe3+ (aq) + 3NH3 (aq) + 3H2O (l) ---> Fe(OH)3 (s) + 3NH4+ (aq)

The precipitate was then collected, washed and transferred to a crucible to heat it that resulted in the production of iron (III) oxide (Fe2O3).

2Fe(OH)3 (s) ---> Fe2O3 (s) + 3H2O (g)

The mass of iron (III) oxide produced was 10.99 g. iron(III) oxide that is produced has a mass of iron equal to 10.99*55.847/159.69 g = 3.84 g

3.84 is 384/8 % of 8 = 48%

This gives the concentration of iron in the original sample as 48%

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