2. An iron ore was analyzed by dissolving a 1.1324 g sample in concentrated HCI.

Question

2. An iron ore was analyzed by dissolving a 1.1324 g sample in concentrated HCI. The resulting solution was diluted with water, and the iron(III) was precipitated as the hydrous Fe,0, "XH,O by the addition of NH,. After filtration and washing, the residue was ignited at a high temperature to give 0.5394 g of pure Fe,0, (159.69 g/mol). Calculate.. a. The % of Fe (55.847 g/mol) b. The % of Fe,0, (231.54 g/mol) in the sample 3. Create a method for the gravimetric analysis of of cadmium in water samples.

Explanation / Answer

a. The total mass of the compound Fe2O3 is given to be 159.69g/mol.

Mass of Fe in this compound is 2x55.847= 111.694g/mol where 55.847g/mol is the Atomic mass of Fe

Percentage of iron in 1g of Fe2O3 = (111.694/159.69)*100 = 0.699*100 = 69.9%

percentage of iron (Fe) in 0.5394g of this compound = 0.699x0.5394x100 = 37.70%

b. The sample of iron ore weighed 1.1324g , of which 0.5394g was Fe2O3

If remaining sample consisted of Fe3O4

%age of Fe3O4 = (0.593/ 1.1324)*100 = 52.36 %

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