The Law of Definite Proportions holds true for compounds but not for mixtures. Class 9

The Law of Definite Proportions holds true for compounds but not for mixtures. Class 9

Question 1.

The Law of Definite Proportions holds true for compounds but not for mixtures. Give reason. Class 9

Answer:

In a compound, elements are chemically combined in a fixed ratio by mass, irrespective of the source or method of preparation. This fixed ratio is a characteristic property of the compound. For example, water always contains hydrogen and oxygen in the ratio 1:8 by mass. In a mixture, however, the components are not chemically combined. They can be present in any ratio and the composition of a mixture can vary. For example, a mixture of sugar and water can be prepared in any proportion. Hence, the Law of Definite Proportions does not apply to mixtures.

Question 2.

Students X and Y, both prepared an oxide of copper by combining copper and oxygen in the ratios of 4:1 and 8:2, respectively. Do their results justify the Law of Constant Proportions? Explain. Class 9

Answer:

Yes, their results justify the Law of Constant Proportions.

Student X: ratio of copper to oxygen = 4:1

Student Y: ratio of copper to oxygen = 8:2 = 4:1

Both ratios simplify to 4:1. Since both students obtained the same compound (the same oxide of copper) in the same fixed mass ratio of copper to oxygen, the Law of Constant Proportions is satisfied.