NCERT MCQ CLASS-9 CHAPTER-3 | ATOMS AND MOLECULES | EDUGROWN

NCERT MCQ ON ATOMS AND MOLECULES

1. Which one of the following phrases would be incorrect to use?

(a) A mole of an element

(b) A mole of a compound

(c) An atom of an element

(d) An atom of a compound

Answer: (d) An atom of a compound

2. The mass of a single atom of carbon is

(a) 12 g

(b) 1/12 g

(c) 1.99 × 10^-23 g

(d) 1.99 × 10²³ g

Answer: (c) 1.99 × 10^-23 g

3. Which is not represented by 1 mole of nitrogen gas? 

(a) 6.023 x 10²³ N₂ molecules 

(b) 22.4 L of N₂ at STP 

(c) 6.023 x 10²³ nitrogen atoms 

(d) 28 g of nitrogen

Answer: (c) 6.023 x 10²³ nitrogen atoms 

4. If 12 grams of carbon has n atoms, then the number of atoms in 12 grams of magnesium will be:

(a) 2n

(b) 3n

(c) n/2

(d) n

Answer: (c) n/2

5. Calculate the relative molecular mass of H2S.

(a) 16 a.m.u.

(b) 64 a.m.u.

(c) 18 a.m.u.

(d) 34 a.m.u.

Answer: (d) 34 a.m.u.

6. The Boiling point of water at normal atmospheric pressure is –

(a) 273° k

(b) 373° K

(c) 100° K

(d) 0° k

Answer: (b) 373° K

7. Atom of Hydrogen is

(a) 10⁻¹⁰m

(b) 10⁻⁹m

(c) 10⁻⁸m

(d) 10⁻¹m

Answer: (a) 10⁻¹⁰m

8. The combining capacity of an element is called 

(a) Valency 

(b) Atomicity 

(c) Atomic number 

(d) Valence electron

Answer: (a) Valency 

9. Which of the following is the chemical symbol for nitrogen gas?

(a) N₂

(b) N

(c) N₃

(d) Ni

Answer: (a) N₂

10. Which of the following illustrates the law of conservation of mass?

(a) 12 g of CO reacts with 32 g of 02 to form 44 g of CO₂ 

(b) 1.70 g of AgNO₃ reacts with 0.01 mol of HCl to form 1.435 g of AgCl and 0.63 g of HNO₃

(c) 12 g of C is heated in vacuum and cooling there is no change in mass

(d) 100 g of ice forms 100 g of water liquid on melting

Answer: (b) 1.70 g of AgNO₃ reacts with 0.01 mol of HCl to form 1.435 g of AgCl and 0.63 g of HNO₃

11. The atom is indivisible, was proposed by

(a) Einstein

(b) Lavoisier

(c) Dalton

(d) Proust

Answer: (c) Dalton

12. Identify the correct one from the following statements. 

(a) Elements can be changed into simpler substances

(b) Compound has variable composition 

(c) The mixture has properties similar to its components

(d) Brass is a compound of Copper and Zinc

Answer: (c) The mixture has properties similar to its components

13. The atomic mass of calcium is 40. Calculate the number of moles in 16 grams of calcium.

(a) 0.4 mole

(b) 4 mole

(c) 1/4 mole

(d) 640 mole

Answer: (a) 0.4 mole

14. What is the latin name of sodium?

(a) Kalium

(b) Plumbum

(c) Natrium

(d) None of the above

Answer: (c) Natrium

15. Modern atomic symbols are based on the method proposed by

(a) Dalton

(b) Berzelius

(c) Bohr

(d) Mendeleev

Answer: (b) Berzelius