Class 9 Chemistry Chapter 3 Atoms and Molecules MCQs

Class 9 chemistry MCQs with answers are provided here for chapter 3 Atoms and Molecules. These MCQs are based on CBSE board curriculum and correspond to the most recent Class 9 chemistry syllabus. By practicing these Class 9 Multiple choice questions, students will be able to quickly review all of the ideas covered in the chapter and prepare for the Class 9 Annual examinations as well as other entrance exams such as CTET and KVS.

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Class 9 Atoms and Molecules MCQs

1. The atomic symbol of silver is —————

(a) Si

(b) S

(c) Au

(d) Ag

Ans: (d)

Solution: The atomic symbol of silver is Ag

2. A box contains some identical red colour balls labelled as A each weighing 2 g. Another box contains identical blue colored balls, labelled as B, each weighing 5 g. In the combinations AB, AB₂, A₂B and A₂B₃ which is applicable?

(a) Law of Definite proportion

(b) Law of multiple proportion

(c) Law of conservation of mass

(d) None of the above

Ans: (b)

Solution: According to the law of multiple proportion if an element forms more than one compound with another element for a given mass of an element, masses of other elements are in the ratio of the small whole number.

3. What is the value of Avogadro’s number?

(a) 6.02 x 10^-23

(b) 6.02 x 10²³

(c) 6.02 x 10^-22

(d) 6.02 x 10²²

Ans: (b)

Solution: The value of Avogadro’s number is 6.02 x 10²³

4. What is the chemical formula of sodium carbonate?

(a) Na₂CO₃

(b) NaHCO₃

(c) NaCO₃

(d) Na₂HCO₃

Ans: (a)

Solution: The chemical formula of sodium carbonate is Na₂CO₃

5. Which of the following is the correct pair of atom and its atomic symbol?

(a) Sulphur – Su

(b) Potassium – P

(c) Phosphorus -P

(d) Sodium- S

Ans: (c)

Solution: The correct pair of atom and its atomic symbol is Phosphorus -P

6. How many moles are present in 40 g of He?

(a) 5 moles

(b) 20 moles

(c) 6 moles

(d) 10 moles

Ans: (d)

Solution: 1 mole of He = 4 gm. ⇒ 40 gm of He = 10 moles

7. Atomic mass of Chlorine is ————– (u)

(a) 34

(b) 34.5

(c) 35

(d) 35.5

Ans: (d)

Atomic mass of Chlorine is 35.5 u

8. 46 gm of sodium is equal to ————-

(a) 7 moles

(b) 1.5 moles

(c) 2 moles

(d) 1 mole

Ans: (c)

Solution: 1 mole of sodium = 23gm, 46 gm of sodium = 2 moles

9. The formula of Ammonium Sulphate is —————–

(a) NH₄SO₄

(b) NH₄SO₂

(c) (NH₄)₂SO₄

(d) NH₂SO₄

Ans: (c)

Solution: The formula of Ammonium Sulphate is (NH₄)₂SO₄.

10. The atomic symbol of Iron is —————.

(a) I

(b) Fe

(c) Ir

(d) Au

Ans: (b)

Solution: The atomic symbol of Iron is Fe.

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