CBSE - Atoms and Molecules

1 Atoms and Molecules 

Which of the following is an element ?

(1) Mercury
(2) Ammonia
(3) Water
(4) Glucose

2 Atoms and Molecules 

Which one of the following is the smallest in size ?
(1) N^3–
(2) O^2–
(3) F^–1
(4) Na⁺

3 Atoms and Molecules 

The pH value of a solution prepared by dissolving 4g NaOH in 100 litre of water is

(1) 13
(2) 14
(3) 12
(4) 11

4 Atoms and Molecules 

Sodium azide NaN₃ decomposes explosively to sodium metal and nitrogen gas and is used in automobile air bags.
2NaN₃ -->  2Na + 2 N₂
Azide ion is iso electronic to ....

(1) CO
(2) NO
(3) CO₂
(4)H₂O

5 Atoms and Molecules 

The valency of the element with atomic number 10 is . . . . . . .

(1) 2
(2) 8
(3) 10
(4) 0

6 Atoms and Molecules 

Molecular mass of H₂SO₄  is ......

(1) 58.5 (u)
(2) 98 (u)
(3) 36.5 (u)
(4) 35.5 (u)
 

7 Atoms and Molecules 

The number of atoms in 0.1 mole of Sodium (Na) is

(1) 6.022 × 10²³
(2) 6.022 × 10²²
(3) 6.022 × 10²¹
(4) 6.022 × 10²⁴

8 Atoms and Molecules 

You have the mythical metal element 'X' that can exhibit variable valences 1, 2 and 5. Which of the following is/are not the correct chemical formula/formulae for the compounds formed by the combination of the "X" ions with different radicals ?

(A) XPO₄ (B) X₂SO₄ (C) X₅ClO₄ (D) X₃NO₃

(1) Only B
(2) B and C
(3) A, C and D
(4) B and D 

9 Atoms and Molecules 

You are provided wit h 64 g of sulphur in cont ainer A and 64 g of O₂  in container B. Which will have more number of molecules ? (Atomic mass of S=32, O=16)

(1) 64 g of S
(2) 64 g of O₂
(3) both have equal number of molecules
(4) cannot calculate with the given information.

10 Atoms and Molecules 

The number of atoms constituting a molecule is known as ........

(1) valency
(2) atomicity
(3) mole concept
(4) atomic mass