Atoms and Molecules Worksheet-5

Atoms and Molecules Worksheet-5

11. The value of Avogadro’s  constant is :

A. 6.0 × 10²⁴                                  B. 6.022 × 10²²

C. 6.022 × 10²³                             D. 6.022 × 10^–23

12. The atomic mass of calcium is 40 u. The number of calcium atoms in 0.4 u of calcium is :

A. 6.022 × 10¹⁰                             B. 6.022 × 10²²

C. 6.022 × 10²³                             D. 6.022 × 10²¹

13. A sample of pure water irrespective of its source contains 88.89% oxygen and 11.11% hydrogen by mass. The data is in accordance with-

A. Law of conservation of mass

B. Law of constant proportion

C. Dalton’s Atomic theory.

D. Avogadro’s Law.

14. The atomic mass of calcium (C_a) is 40 g. The number of moles in 60 g of calcium are :

A. 0.5 mol          B. 2.0 mol         C. 1.5 mol          D. 0.75 mol

15. Which of the following is not correct according to Dalton’s atomic theory?

A. Atoms are indivisible.

B. Atoms combine in simple whole number ratios.

C. All atoms of an element may not have same mass.

D. Atoms of different elements have different masses.

16. Percentage of calcium in calcium carbonate is :

A. 40                   B. 30                   C. 48                   D. 36

17. Correct formula of Ferric sulphate is :

A. FeSO₄            B. Fe(SO₄)₂       C. Fe₃(SO₄)₂      D. Fe₂(SO₄)₃

18. A chemical equation is always balanced in accordance with:

A. Dalton’s atomic theory

B. Law of constant composition

C. Law of multiple proportions.

D. Law of conservation of mass.

19. How many moles are there in 0.6 g of SO₂?

A. 100                 B. 10                    C. 0.01                D. 0.1

20. The number of molecules in 4.25 g of  NH₃  is approximately :

A. 1.5 × 10²³      B. 2 × 10²³         C. 4 × 10²³         D. 6 × 10²³

Answer:

11. C

Explanation: Fact

12. D

Explanation:

13. B

Explanation: Law of constant proportion: A pure chemical compound always consists of the same elements that are combined together in a fixed (or definite) proportion by mass.

14. C

Explanation:

No. of moles in 60 g of calcium

15. C

Explanation: All atoms of an element have same mass according to Dalton atomic theory.

16. A

Explanation: Percentage of Ca = 40 %

17. D

Explanation: The valency of iron in Ferric sulphate is 3. Formula Fe₂(SO₄)₃

The valency of iron in Ferrous sulphate is 2. Formula FeSO₄.

18. D

Explanation: A chemical equation is balanced according to law of conservation of mass.

19. C

Explanation: Number of moles in 0.64 g of SO₂ .

20. A

Explanation: Gram molecular weight of ammonia = 18 g

18 g ammonia = 1 mole

4.25 g ammonia =