Question

The mineral haematite is $F{e_2}{O_3}$.Haematite ore contains unwanted material called gangue in addition to $F{e_2}{O_3}$ . If $5$ kg of ore contains $2.78$ kg of Fe,the percentage purity of $F{e_2}{O_3}$ is
A. $55.6\%$
B. $44.4\%$
C. $20.6\%$
D. $79.4\%$

Answer 1

Minerals are naturally occurring solid substances that are made up of one or more elements combined. Ore is the mineral from which metal is extracted. Gangues are the impurities within the ore. Before the ore is subjected to any metallurgical process, the impurities are removed and are known as concentration of ore. The unwanted material gangue is present in the haematite which lowers the percentage purity.

Complete step by step answer:
As it is given that $5$ kg of ore contains $2.78$ kg of iron which shows there are some impurities in the ore.
So the amount of iron which is present in haematite is $2.78$ kg
Percentage purity is calculated by dividing the mass of pure chemical by total mass of the sample which is then multiplied by 100
So the percentage of iron present in haematite is
The amount of iron is $\dfrac{{112}}{{160}} \times 100 = 70\%$
So the percentage of iron present is seventy percent.
Therefore the actual mass of ferric oxide is $\dfrac{{2.78}}{{70}} \times 100 = 3.9714$ kg
Therefore the percentage purity of ferric oxide is a mass of ferric oxide divided by the mass of mineral that is
$\dfrac{{3.97}}{5} \times 100 = 79.4\%$
Therefore the percentage purity of ferric oxide is $79.4\%$ .

So, the correct answer is Option D.

Note: The given mass and the actual mass of ferric oxide present are different to be calculated as there is some impurity in the form of gangue in the mineral ore. Haematite is a hard oxide mineral. It is the most important iron ore because of its high iron content.