Explore the fascinating world of MCQ Science Class 9 atoms and molecules with our comprehensive MCQ (Multiple Choice Questions) for Class 9 Science, Chapter 3. This carefully crafted set of questions will test students’ understanding of fundamental concepts and help reinforce their knowledge. Each question is thoughtfully accompanied by precise answers, providing a valuable resource for effective exam preparation and enhancing overall learning in this crucial subject. Get ready to unravel the mysteries of the microcosmic realm!
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 unit or (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 are 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 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 a 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 a 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. The 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 a 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 has 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
Q31. What is the most fundamental unit of matter that makes up everything around us?
a) Molecules
b) Compounds
c) Atoms
d) Elements
Answer: c) Atoms
Q32. In a chemical reaction, what are the newly formed compounds called?
a) Ingredients
b) Elements
c) Products
d) Reactants
Answer: c) Products
Q33. According to the law of conservation of mass, what happens to matter in a chemical reaction?
a) It is created
b) It is destroyed
c) It remains conserved
d) It changes form
Answer: c) It remains conserved
Q34. What is the law that states a pure chemical compound contains the same elements combined together in a fixed proportion by mass?
a) Law of Conservation of Mass
b) Law of Constant Proportions
c) Law of Chemical Combination
d) Law of Atomic Radius
Answer: b) Law of Constant Proportions
Q35. Who is credited with formulating the Law of Constant Proportions?
a) Dalton
b) Proust
c) Mendeleev
d) Einstein
Answer: b) Proust
Q36. What is the atomic radius defined as?
a) The size of an atom
b) The number of protons in an atom
c) The mass of an atom
d) The distance between the nuclei of two bonded atoms
Answer: d) The distance between the nuclei of two bonded atoms
Q37. According to Dalton’s Atomic Theory, what is the smallest, indivisible unit of matter?
a) Molecule
b) Compound
c) Atom
d) Element
Answer: c) Atom
Q38. What property of atoms did Dalton propose was the same for all atoms of a given element?
a) Mass and chemical properties
b) Size and mass
c) Chemical properties and reactivity
d) Mass and size
Answer: a) Mass and chemical properties
Q39. According to Dalton’s Atomic Theory, what happens to atoms in a chemical reaction?
a) They are created
b) They are destroyed
c) They change in size
d) They rearrange to form new compounds
Answer: d) They rearrange to form new compounds
Q40. What remains constant in a given compound, according to Dalton’s Atomic Theory?
a) The number of atoms
b) The mass of atoms
c) The type of atoms
d) The ratio of atoms
Answer: d) The ratio of atoms