20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0g magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample ? (NEET 2015)

Given, Weight of magnesium carbonate ( 3 MgCO ) = 20.0 g Weight of magnesium oxide ( MgO) = 8.0 g The molecular mass of magnesium carbonate ( 3 MgCO ) = 24 12 3 16 24 12 48 84 g x The molecular mass of magnesium oxide ( MgO) = 24 16 40 g Chemical decomposition of magnesium carbonate on heating is 3 2 MgCO MgO CO → Weight of magnesium Weight of magnesium carbonate oxide 84 g 40 g (as per balanced reaction) 20.0g x g Solving for x, we get 40 20 800 9.52380952