Question

On analysis it was found that the black oxide of copper and red oxide of copper contain 80%
and 89% of copper respectively. Show that this data is in accordance with law of multiple proportions.​

Answer 1

Black oxide of copper = CuORed oxide of copper = Cu2OGiven % of copper in CuO = 80 %So % of oxygen = 20 %Given % of copper in Cu2O = 89 %So % of oxygen = 11 %

20 g of oxygen combines with 80 g of metalSo 8 g of oxygen combines with = 8020 × 8 = 32 g11 g of oxygen combines with 89 g of metalSo 8 g of oxygen combines with = 8911 × 8= 64.72 gThus the weight of metal are = 32 : 64.72 ≈ 1 : 2Thus for the fixed weight of oxygen (8 g- equivalent mass of O) the amount ofmetal combined = 1 : 2Thus law of multiple proportion is obeyed.