Question

In an experiment, 1.50 g of pure copper (ll) oxide was reduced to pure metal by heating with pure carbon. In another experiment, 1.15 g of pure copper was treated with nitric acid and the product formed was heated strongly till no further change was observed. The mass of copper (ll) oxide so formed was found to be 1.40 g. The mass of pure metal in the first experiment and the law followed are respectively

Answer 1

It is given that in the first experiment 1.50 g of copper II oxide was reduced to give pure copper and in another experiment it is given that 1.15g of copper has given 1.40g of copper II oxide.
In according to law of definite proportions the ratio of mass of reactants in a product will be same in all cases.
So 1.15g copper will give 1.40g of Copper II oxide. The mass of copper required for 1.50g copper oxide is
Cu . CuO
1.15g . 1.40g
? 1.50g
so ?= 1.50x1.15/1.40 = 1.23g
Hence the mass of copper in first experiment is 1.23g and the law followed is Law of Definite Proportions.