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)

20.0 g of a magnesium carbonate sample decomposes on heating to give c

1.	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)
Answer» (B) 84Explanation:Quantity of magnesium carbonate ( MgCO3) = 20gQuantity of magnesium oxide ( MgO ) = 8gThe balanced equation will be - MgCO3 → MgO + CO2Therefore, 84g of MgCO3 = 40g of MgO20g of MgCO3 = 40/84 × 20MgO = 9.52Actual yeild = 8G of MgOThus, PURITY % = 8/ 9.52 × 100= 84%THEREFORE, the percentage purity of magnesium carbonate in the sample will be 84%.