Question

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) 75
(b) 96
(c) 60
(d) 84

Answer 1

Answer:

MgCO₃ ⇒ MgO + CO₂

84g 40g

y g 8 g (y is variable used)

y=(84 x 8)/40 = 16.8 g

Percentage purity of MgCO₃ = (16.8 x 100)/20=84%