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Some Basic Concepts of Chemistry
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13/08/2021 10:39 am
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2.0 g of a sample contains mixture of SiO2 and Fe2O3. On very strong heating, it leaves a residue weighing 1.96 g. The reaction responsible for loss of mass is given below
Fe2O3(s) → Fe2O4(s) + O2(g), (unbalance equation)
What is the percentage by mass of SiO2 in original sample?
(a) 100 %
(b) 20 %
(c) 40 %
(d) 60 %
1 Answer
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13/08/2021 10:43 am
Correct answer: (c) 40 %
Explanation:
3Fe2O3(s) → 2Fe2O4(s) + \(\frac{1}{2}\)O2(g)
480 g Fe2O3 provide 16 g O2. For loss of 0.04g
O2 → 0.04 x \(\frac{480}{16}\) = 1.2 g Fe2O3
% by mass of SiO2 = \(\frac{0.8}{2.0}\) x 100 = 40%