Determine the percentage composition (by mass ) of a mixture of anhydrous sodium carbonate and sodium bicarbonate from the following data
weight of the mixture taken =2g
Loss in weight on heating =0.11gm

When the mixture of sodium carbonate and sodium bicarbonate (2 g) is heated, then sodium bicarbonate decomposes to give sodium carbonate, water and carbon-di-oxide, which are evolved as gases. Therefore the loss in the weight (0.11 g) of the mixture will be due to evolution of theses gases
62 g (18g+44g) of gas is produced from 168 g of Sodium Bicarbonate.
Therefore, 0.11 g of gas will be produced form (0.11x168)/62 = 0.298 g of Sodium Bicarbonate.
The weight of sodium bicarbonate is 0.298 g, so, weight of sodium carbonate will be (2g-0.298 g) = 1.702g.