In an experiment, 1.288 g of copper oxide was obtained from 1.03 g of Cu. In another experiment, 3.672 g of copper oxide gave on reduction 2.938 g of copper. Which law of chemical combination can be illustrated by this example?
(1) Law of conservation of mass
(2) Law of constant proportion
(3) Law of multiple proportion
(4) None of these
Answer (2)
The question illustrates the Law of Constant Proportion, which states that a chemical compound always contains its elements in a fixed mass ratio. Both experiments show consistent ratios between the mass of copper and copper oxide. Hence, the chosen option is (2) Law of Constant Proportion.
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In the question presented, we have two separate experiments involving copper oxide and copper.
In the first experiment, 1.288 g of copper oxide is obtained from 1.03 g of copper.
In the second experiment, 3.672 g of copper oxide was reduced to give 2.938 g of copper.
To determine which law of chemical combination these experiments illustrate, we should look at the ratios of copper to copper oxide in each experiment:
First experiment: The mass of copper is 1.03 g and the mass of copper oxide is 1.288 g. The ratio of the mass of copper to copper oxide is: Ratio = 1.288 1.03 = C u O C u ≈ 0.8
Second experiment: The mass of copper is 2.938 g and the mass of copper oxide is 3.672 g. The ratio of the mass of copper to copper oxide is: Ratio = 3.672 2.938 = C u O C u ≈ 0.8
Both experiments give approximately the same ratio of copper to copper oxide, which shows that no matter the amount of copper oxide formed or reduced, the proportion of copper (by mass) remains consistent.
This scenario is a perfect illustration of the Law of Constant Proportion (also known as the Law of Definite Proportions) . According to this law, a chemical compound always contains exactly the same proportion of elements by mass.
Thus, the correct answer to the question is option (2) Law of constant proportion .
