NIOS Class 10 Science and Technology Chapter 3: ATOMS AND MOLECULES –Chapter-wise Important Questions and Answers

NIOS Class 10 Science and Technology Chapter 3: ATOMS AND MOLECULES |MCQs, Short & Long Answer Questions | 3. ATOMS AND MOLECULES

Chapter 3: ATOMS AND MOLECULES

INTEXT QUESTIONS 3.1

1. Name the scientists who proposed the law of conservation of mass and law of constant proportions.

Answer:  The law of conservation of mass was proposed by Antoine Lavoisier.

The law of constant proportions was proposed by Joseph Proust.

 

2. 12 g of magnesium powder was ignited in a container having 20 g of pure oxygen. After the reaction was over, it was found that 12 g of oxygen was left unreacted. Show that it is according to law of constant proportions.

2Mg + O2→ 2MgO

Answer: The chemical equation is given below,

2Mg + O2→ 2MgO

In container, 12g of Oxygen was left unreacted.

Therefore, amount of unreacted oxygen = (20 – 12)g = 08g.

Thus 12g of magnesium reacted with 8g of Oxygen in the ratio 12:8.

This is what we expected for MgO i.e 24g of Mg reacted with 16g of Oxygen or 12g of Mg will react with 8g of Oxygen.

Therefore, the observation obeys the law of constant proportions.

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