20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0 g magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample?
(A) 60
(B) 84
(C) 75
(D) 96
(At. Wt. : Mg = 24)
Answers
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Answer:
(B) 84
Explanation:
Quantity of magnesium carbonate ( MgCO3) = 20g
Quantity of magnesium oxide ( MgO ) = 8g
The balanced equation will be -
MgCO3 → MgO + CO2
Therefore,
84g of MgCO3 = 40g of MgO
20g of MgCO3 = 40/84 × 20
MgO = 9.52
Actual yeild = 8g of MgO
Thus,
Purity % = 8/ 9.52 × 100
= 84%
Therefore, the percentage purity of magnesium carbonate in the sample will be 84%.
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