CBSE Class 9 Science Atoms and Molecules MCQs Set 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 formula of Calcium phosphate is:
(a) CaPO₄
(b) Ca(PO₄)₂
(c) Ca₃(PO₄)₂
(d) Ca₂(PO₄)₃

Answer : C

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

Answer : A

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

Answer : D

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) I
(b) Iv< i
(c) I
(d) Iv

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) 1g of oxygen gas
(b) 1g of oxygen atoms
(c) 1 g of ozone
(d) All have equal number of atoms

Answer : D

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

Answer : C

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

Answer : D

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

Answer : D

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

Answer : A

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

Answer : C

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, oxygen
(b) 16u, Sulphur
(c) 32u, oxygen
(d) 32u, Sulphur

Answer : A

Question.
(a) Oxygen:
(b) diatomic
(c) Ozone :_______
i. Monoatomic
ii. Diatomic
iii. Triatomic
iv. Tetra atomic

Answer : C

Question.
(a) 24g of Mg: 1 mole
(b) 35.5g of Cl₂: _________
i. 0.5mol
ii. 1 mol
iii. 2moles
iv. 2.5 moles

Answer : A