Question

1. Who established the two important laws of chemical combinations?

2. What are the laws of chemical combinations?

3. What is the law of conservation of mass?

4. Give an example to show Law of conservation of mass applies to physical change also.

5. Explain with example that law of conservation of mass is valid for chemical reactions.

6. The 2.8 g of nitrogen gas was allowed to react with 0.6 g of hydrogen gas to produce 3.4 g

of ammonia. Show that these observations are in agreement with the law of Conservation

of mass.

7. If 12 g of carbon is burnt in the presence of 32 g of oxygen, how much carbon dioxide will

be formed?

8. Who proposed Law of Definite Proportions (or Law of Constant Composition)?

9. State Law of constant proportions. Explain with an example.

10. Show that water illustrates the law of constant proportions.

11. Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of

oxygen gas would be required to react completely with 3 g of hydrogen gas?

12. A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096

g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound

by weight.

13. When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced.

What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of

oxygen? Which law of chemical combination will govern your answer?

14. Magnesium and oxygen combine in the ratio of 3 : 2 by mass to form magnesium oxide.

How much oxygen is required to react completely with 12 g of magnesium?

15. What are the postulates of Dalton's atomic theory?

16. Which of the following statements is NOT true about an atom?

(a) Atoms are the building blocks from which molecules and ions are formed.

(b) Atoms cannot exist independently.

(c) Atoms are neutral in nature

(d) Atoms combine together to form matter that we can see, feel or touch.

17. What is an atom?

18. Why is it not possible to see an atom with naked eyes?

19. Who proposed the chemical notation based on first two letters of the name of the element?

20. Name the international organization who approves names of elements.

21. What is the chemical symbol for iron?

22. Name five elements have single letter chemical symbol.​

Answer 1

Answer:

1. Lavoser proposed laws of chemical combination

2. law of conservation of mass and law of constant proportions are called law of chemical combination

3 mass neither be created nor be destroyed

4