Atoms and Molecules MCQ Class 9

MCQ Questions for Class 9 Science Chapter 3 Atoms and Molecules with Answers

Q1. Around 500 BC, an Indian philosopher postulated that “if we divide matter, we shall get smaller and smaller particles. ultimately, a stage will come when the further division of matter will not be possible”.

a) Maharishi kanad

b) Pakudha katyayama  

c) John Dalton

d) Lavoisier 

Ans :- Maharishi kanad

Q2. Which Scientist put forward the “law of conservation of mass”?

a) pakudha katyayama 

b) Democritus

c) A. Lavoiser 

d) None of the above 

Ans :- A. Lavoisier

Q3. What does the “Law of conservation of mass” state 

a) Indivisibility conservative mass of the atom 

b) In a chemical substance the elements are always present in definite proportions by mass

c) Mass can neither be created nor destroyed in a chemical reaction

d) None of these  

Ans :- Mass can neither be created nor destroyed in a chemical reaction

Q4. Which of the following is known as “Laws of chemical combination”? 

a) Law of Constant proportions

b) Law of conservation of mass

c) None (a) and (b) 

d) Both (a) and (b) 

Ans :- Both (a) and (b)

Q5. What does the “Law of Constant proportions” state

a) Mass can neither be created nor destroyed in a chemical reaction 

b) In chemical substance the elements are always present in definite proportions by mass 

c) It states that the value of elements present in same number in chemical reaction

d) All of these 

Ans :- In chemical substance the elements are always present in definite proportions by mass 

Q6. What is the full form of ‘IUPAC’ :- 

a) International Union of Pure and Applied Chemistry 

b) Inter Union Part of Applied Chemistry

c) International Unified Part of Applied Chemical reaction 

d) None of the above 

Ans :- International Union of Pure and Applied Chemistry 

Q7. In a compound such as water, the ratio of the mass of hydrogen to the mass of oxygen is always ______ in ratio.

a) 1 : 8 

b) 3 : 16

c) 1 : 2 

d) none of these 

Ans :- 1 : 8 

Q8. Which statement is true about Dalton’s atomic theory ?

a) Atoms of different elements have different masses and 

chemical properties

b) Atoms of a given element are identical in mass and

chemical properties 

c) All matter is made of very tiny particles called atoms

d) All of the above 

Ans :- All of the above 

Q9. The relative number and kinds of atoms are ________ in a given compound.

a) same 

b) constant 

c) different 

d) relative 

Ans :- constant 

Q10.  atomic radius is measured in nanometres are :- 

a) 1m = 10-¹⁰ nm

b) 1m = 10-⁹nm

c) 1nm = 10-⁹ m

d) 1nm = 10-¹⁰ m

Ans :- 1 nm = 10-⁹ m

Q11. 1 atomic mass unitor (1amu) or 1 unified atomic mass unit (1u) is exactly equals to 

a) Mass of one atom of Carbon— 12 atom   

b) 1/12th mass of one atom of carbon— 12 atom

c) Mass of one atom of Hydrogen

d) None of these 

Ans :- 1/12th mass of one atom of carbon— 12 atom

Q12. What is the atomic symbols of ‘Lead or Iron’ elements :-

a) Le or Ir 

b) Pb or Fe 

c) Ld or Io

d) La or In 

Ans :- Pb or Fe  

Q13. Which of the following statements is not true about an atom ?

a) Atoms are not able to exist independently.

b) Atoms are the basic unit from which the molecules and ions are formed.

c) Atoms are always neutral in nature.

d) Atoms aggregate in large numbers to form the matter that we can see, feel or touch.

Ans :-  Atoms aggregate in large numbers to form the matter that we can see, feel or touch.

Q14. The smallest particle of an element or a compound that is capable of an independent existence and shows all the properties of that substance, It is called :- 

a) Atoms 

b) Compound 

c) Molecules 

d) None of these 

Ans :- Molecules 

Q15. Which statement is not true about the molecules ?

a) Molecules combine in the ratio of small whole number to

form compounds. 

b) Molecules of an element constitute the same type of atoms.

c) Molecules may be monoatomic, diatomic or polyatomic. 

d) Molecules of compounds join together in definite  proportions and constitute a different type of atom.

Ans :- Molecules combine in the ratio of small whole numbers to form compounds.

Q16. The number of atoms present in molecule of substance is known as :- 

a) Valency 

b) Atomicity 

c) Molecularity 

d) Reactivity 

Ans :- Atomicity 

Q17. What is the Atomicity of Chlorine and Argon?

a) Monoatomic and Diatomic  

b) Monoatomic and Tetra-atomic

c) Diatomic and Monatomic 

d) Diatomic and poly-atomic

Ans :- Diatomic and Monatomic

Q18. The charged species are known as :- 

a) ions 

b) cation

c) anion

d) none 

Ans :- ions 

Q19. A group of atoms carrying a charge is known as :- 

a) Tetra-atomic ions 

b) poly-atomic ions

c) Monoatomic ions 

d) Diatomic ions 

Ans :- polyatomic ions

Q20. Mass of 1 mole of a substance is called its :-

a) Mole mass

b) Molar mass 

c) weight 

d) none of these 

Ans :- Molar mass

Q21. Which rule/statement is true about the chemical formulae

a) The valencies or charge on the ions must balance

b) Metal and non-metal compounds should show the name or symbol of the metal first

c) If a compound consists of polyatomic ions. The ions is enclosed in a bracket before writing the number to indicate the ratio 

d) All of these 

Ans :- All of these 

Q22. Avogadro number is equal to :-

a) 6.021×10²¹

b) 6.020×10²²

c) 6.022×10²³

d) 6.023×10²⁴

Ans :- 6.022×10²³

Q23. The combining power (or capacity) of an element is known as :- 

a) Valency 

b) Atomic Number 

c) Valence Electron

d) None of these 

Ans :- Valency

Q24. The formula unit mass of a substance is the sum of the _____ of all the atoms in a formula unit of a compound.

a) atomic masses 

b) Valence Electron  

c) atomic number 

d) All of these 

Ans :- atomic masses 

Q25. Calculate the formula unit mass of NaCl.

a) 46.5 u 

b) 30 u 

c) 35.5 u 

d) 58.5 u

Ans :- 58.5 u

Q26. The mass of one mole of substance is equal to its :- 

a) relative atomic 

b) molecular mass

c) Both (a) and (b) 

d) None (a) and (b) 

Ans :- Both (a) and (b) 

Q27. Which of the following correctly represents 360g of water.

i) 20 moles of water 

ii) 32 moles of water 

iii) 1.2044×10²⁵ molecules of water 

iv) 6.022×10²³ molecules of water 

a) (i) and (iii)

b) (i) and (iv)

c) (ii) and (iii)

d) (iii) and (iv)

Ans :- a) (i) and (iii)

Q28. Compare the number of molecules in 100g of ammonia(NH3) and 100 g of nitrogen (N2).

a) nitrogen have more molecules 

b) ammonia(NH3) have more molecules 

c) Both are equal 

d) None of these

Ans :- ammonia(NH3) have more molecules

Q29.  Find out the percentage composition of oxygen elements present in sulphuric acid?

a) 2.04%

b) 32.63%

c) 65.3%

d) None of the above 

Ans :- 65.3%

Q30. What is the value of 1amu ?

a) 1.621×10-²⁵ kg 

b) 1.622×10-²⁶ kg 

c) 1.622×10-²⁷ kg 

d) 1.621×10-²³ kg 

Ans :- 1.622×10-²⁷ kg

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