Question

Determine the percentage composition of a mixture of anhydrous na2co3 and nahco3

Answer 1

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 as shown below:
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-0.298g) = 1.702g.