CBSE Class 9 Science Atoms and Molecules MCQs

Question: Which of the following is not a postulate of Daltons atomic theory:
(a) Atoms of different elements can have the same mass
(b) All matter is made up of atoms
(c) Atoms are tiny indivisible and indestructive ultimate particles
(d) Atoms combine in small whole number ratios to form compounds

Answer: A

Question: a. 24g of Mg: 1 mole
              b. 35.5g of Cl₂: _________

(a) 0.5mol
(b) 1 mol
(c) 2moles
(d) 2.5 moles

Answer: A

Question: a. Oxygen: diatomic
                  b. Ozone :_______

(a) Triatomic
(b) Monoatomic
(c) Diatomic
(d) Tetra atomic

Answer: A

Question: The mass of a single atom of an element X is 2.65X 10-²³g. The atomic mass and name of the element is:
(a) 16u, Sulphur
(b) 16u, oxygen
(c) 32u, oxygen
(d) 32u, Sulphur

Answer: B

Question: An element X has valency equal to 3. What will be its formula with carbonate ions?
(a) X₂(CO₃)3
(b) X₂CO₃
(c) XCO₃
(d) X(CO₃)₃ 

Answer: A

Question: Which of the following has the smallest number of molecules?
(a) 2g of H₂ at STP
(b) 3.4g of NH₃
(c) 0.1 moles of CO₂
(d) 16g of O₂ gas

Answer: C

Question: 16g of S8 contains:
(a) 6.023x10²³/16 atoms of S
(b) 6.023x10²³ Atoms of S
(c) 6.023x10²³/8 atoms of s
(d) 6.023x10²³/2 atoms of S

Answer: A

Question: The number of atoms present in 0.5 moles of Nitrogen atoms is same as in:
(a) 12 g of C
(b) 8 g of O
(c) 24 g of Mg
(d) 32 g of S

Answer: B

Question: Out of 1 g of oxygen gas, 1 g of oxygen atoms and 1g of ozone , maximum number of atoms are present in:
(a) All have equal number of atoms
(b) 1g of oxygen gas
(c) 1g of oxygen atoms
(d) 1 g of ozone

Answer: A

Question: Arrange the following in increasing number of molecules:
i. 0.5moles of H₂ 
ii. 4g of H₂ 
iii. 18g of H₂O
iv. 2.2g of CO₂ 
(a) iv < i < iii < ii
(b) i < iii < iv < ii
(c) iv < iii < ii < i
(d) i < ii < iii < iv

Answer: A

More Questions.......................

Question: How many moles of electrons weigh 1 kg. Mass of an electron is 9.1X10-³¹
(a) 10⁸/9.1X6.022
(b) 6.022X10²³
(c) 6.022X10²³/9.1X10-³¹
(d) 1X10³¹/9.1

Answer: A

Question: Molecular weight of CuSO₄.5H₂O is equal to:
(a) 159.5 X90
(c) 249.5
(b) 159.5
(d) 159.5 +10 + 16

Answer: C

Question: The formula of Calcium phosphate is:
(a) Ca₃(PO₄)₂
(b) CaPO₄
(c) Ca(PO₄)₂
(d) Ca2(PO₄)₃ 

Answer: A

Question: Which of the following is a correct statement:
(a) Na₂S is sodium sulphide, Na₂SO₃ is sodium sulphite, Na₂SO₄ is sodium sulphate
(b) Na₂S is sodium sulphite, Na₂SO₃ is sodium sulphide, Na₂SO₄ is sodium sulphate
(c)Na₂S is sodium sulphide, Na₂SO₃ is sodium sulphate, Na₂SO₄ is sodium sulphite
(d) Na₂S is sodium sulphite, Na₂SO₃ is sodium sulphite, Na₂SO₄ is sodium sulphide

Answer: A

Question: The balancing of chemical equations is in accordance with:
(a) Both b and c
(b) Law of combining volumes
(c) Law of constant proportions
(d) Law of conservation of mass

Answer: A

Question: 18g of water is electrolyse The weight of oxygen obtained is:
(a) 8g
(b) 16g
(c) 4g
(d) 1g

Answer: B

Question: Which is not represented by 1mole of Nitrogen gas?
(a) 6.023X10²³ atoms of N₂
(b) 6.023X10²³ molecules of N₂
(c) 12.046 X10²³ atoms of N₂
(d) 28g of N₂ 

Answer: A

Question: The combining capacity of an element is called
(a) Valency
(b) Atomicity
(c) Atomic number
(d) Valence electrons

Answer: A

Question: Identify the correct symbol of gold:
(a) Au
(b) Go
(c) Ge
(d) Gd

Answer: A

Question: If isotopic distribution of C-12 & C-14 is 98% and 2% respectively, then number of C-14 atoms in 12 g of C is:
(a) 1.244X10²²
(b) 1.244X10²³
(c) 3.88X10²²
(d) 3.88X10²² 

Answer: A

Question: Which of the following contains maximum number of molecules?
(a) 19 CO₂
(b) 1 g N₂
(c) 1 g H₂
(d) 1 g CH₄ 

Answer : C

Question: The molecular formula of potassium nitrate is ________.
(a) KNO₃
(b) KNO
(c) KNO₂
(d) KON

Answer : A

Question: What is the latin name of sodium?
(a) Kalium
(b) Plumbum
(c) Natrium
(d) None of the above

Answer : C

Question: The combining capacity of an element is called
(a) Valency
(b) Atomicity
(c) Atomic number
(d) Valence electron

Answer : A

Question: Which of the following statements is not true about an atom?
(a) Atoms are not able to exist independently.
(b) Atoms are the basic units from which 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.

Answer : D

Question: The law of definite proportions was given by:
(a) John Dalton
(b) Humphry davy
(c) Proust
(d) Michael Faraday

Answer : C

Question: The most remarkable concept that Dalton’s atomic theory proposed was that of the:
(a) atomic weight
(b) atomic mass
(c) molar mass
(d) none of the above

Answer : B

Question: Who coined the term ‘Parmanu’ for the smallest indivisible particles?
(a) Leucippus
(b) L. Lavoisier
(c) Kanad
(d) None of them

Answer : C

Question: Identify the correct symbol of Gold.
(a) Go
(b) Gd
(c) Ge
(d) Au

Answer : D

Question: 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

Question: The chemical symbol for barium is:
(a) B
(b) Ba
(c) Be
(d) Bi

Answer : B

Question: The molecular formula of potassium nitrate is ________.
(a) KNO3
(b) KNO
(c) KNO2
(d) KO

Answer : A

Question: The atomic mass of carbon is:
(a) 12
(b) 14
(c) 16
(d) 23

Answer : A

Question: Who coined the term ‘Parmanu’ for the smallest indivisible particles?
(a) Leucippus
(b) L. Lavoisier
(c) Kanad
(d) None of them

Answer : C

Question: The mass of sodium in 11.7 g of sodium chloride is:
(a) 2.3g
(b) 4.6g
(c) 6.9g
(d) 7.1g

Answer : B

Question . Which of the following correctly represents 360g of water?
(i) 2 moles of water
(ii) 20 moles of water
(iii) 6.022 × 1023 molecules of water
(iv) 1.2044 × 1025 molecules of water
(a) (i)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)

Answer. (d) (ii) and (iv)

Question . The molecular formula of potassium nitrate is ________.
(a) KNO₃
(b) KNO
(c) KNO₂
(d) KON

Answer : A

Question . Which of the following contains maximum number of molecules?
(a) 19 CO₂
(b) 1 g N₂
(c) 1 g H₂
(d) 1 g CH₄

Answer : C

Question . 3.42 g of sucrose are dissolved in 18 g of water in a beaker. The numbers of oxygen atoms in the solution are:
(a) 6.68 ×10²³
(b) 6.09 ×10²²
(c) 6.022 ×10²³
(d) 6.022 ×10²¹

Answer : A

Question . What is the formula mass unit of ZnO?
(a) 18 u
(b) 81 u
(c) 88 u
(d) 188 u

Answer : B

Question: The chemical symbol for nitrogen gas is
(a) Ni
(b) N2
(c) N+
(d) N

Answer : B

Question: The molecule having an atomicity of 4 is:
(a) Sulphate molecule
(b) Ozone molecule
(c) Phosphorus molecule
(d) Methane molecule

Answer : C

Question: How many times an atom of sulphur is heavier than an atom of carbon?
(a) 32 times
(b) 12 times
(c) 8/3 times
(d) 12/32 times

Answer : C

Question . Which of the following represents a correct chemical formula?
(a) CaCl
(b) BiPO₄
(c) NaSO₄
(d) NaS

Answer : B

Question : Which of the following statements is not true about an atom?
(a) Atoms are not able to exist independently.
(b) Atoms are the basic units from which molecules and ions are forme(d)
(c) Atoms are always neutral in nature.
(d) Atoms aggregate in large numbers to form the matter that we can see, feel or touch.

Answer : D

Question: Percentage of calcium in calcium carbonate is
(a) 40
(b) 30
(c) 48
(d) 36

Answer : A

Question: The number of oxygen atoms in 4.4 g of CO₂ is approx.
(a) 6 × 10²²
(b) 6
(c) 12 × 10²³
(d) 1.2 × 10²³

Answer : D

Question: The molecule having an atomicity of 4 is:
(a) Sulphate molecule
(b) Ozone molecule
(c) Phosphorus molecule
(d) Methane molecule

Answer : C

Question: Choose the law of conservation of mass
(a) Mass neither be created nor formed
(b) Mass can neither be created nor reform
(c) Mass can neither be created nor destroyed
(d) Mass can neither be created nor alive

Answer : C

Question: The number of molecules in 16.0g of oxygen is:
(a) 6.02 × 10²³
(b) 6.02 ×10−²³
(c) 3.01 × 10−²³
(d) 3.01 × 10−²³

Answer : D

Question: 4g of iodine and 14.2g of chlorine are made to react completely to yield a mixture of ICl and ICl3 . Calculate the ratio of moles of ICl and ICl3 :
(a) 1: 1
(b) 2: 1
(c) 3: 1
(d) 1: 2

Answer : A

Question: One gram of which of the following contains largest number of oxygen atoms?
(a) O
(b) O2
(c) O3
(d) All contains same

Answer : C

Question: The law of definite proportions was given by:
(a) John Dalton
(b) Humphry davy
(c) Proust
(d) Michael Faraday

Answer : C

Question: Atomic radius is measured in…………
(a) Kg
(b) cm
(c) Mm
(d) nm

Answer : D

Question: The chemical symbol for barium is:
(a) B
(b) Ba
(c) Be
(d) Bi

Answer : B

Question : Which of the following represents the correct relation between Avogadro’s number (No), number of particles (N) and moles (n)?
(a) n = N / No
(b) n = No / N
(c) n = N No
(d) all are correct

Answer : A

Question : When an atom loses electrons, it is called a (an) ______ and has a _____ charge.
(a) Anion, positive
(b) Cation, positive
(c) Anion, negative
(d) Cation, negative

Answer : B

Question: Selenium ingested in the amount of 90 micrograms per day causes loss of hair. How many selenium atoms are in this size sample? (Atomic weight: Se = 78.96.)
(a) 6.9 × 1023
(b) 8.8 × 1017
(c) 8.8 × 1022
(d) 6.9 × 1017

Answer : D

Question : …………….. for some elements as proposed by Dalton.
(a) Shape
(b) Initiator
(c) Symbol
(d) Color

Answer : C

Question: The percentage of copper and oxygen in samples of CuO obtained by different methods were found to be the same. The illustrate the law of:
(a) Constant proportion
(b) Conservation of mass
(c) Multiple proportions
(d) Reciprocal proportions

Answer : A

Question: The number of atom in 4.25g of NH3 is approximately:
(a) 1×10²³
(b) 2×10²³
(c) 4×10²³
(d) 6×10²³

Answer : D

Question: How many molecules are present in one gram of hydrogen?
(a) 6.02×10²³
(b) 3.01×10²³
(c) 2.5×10²³
(d) 1.5×10²³

Answer : B