SCIENCE TEXTBOOK FOR CLASS IX>Chapter 3 - Atoms and Molecules>Exercises>Q 6

MEDIUM

9th CBSE

IMPORTANT

Earn 100

Calculate the molar mass of the following substances.
(a) Ethyne, $C_{2} H_{2}$
(b) Sulphur molecule, $S_{8}$
(c) Phosphorus molecule, $P_{4}$ (Atomic mass of Phosphorus = $31 u$ )
(d) Hydrochloric acid, $H C l$
(e) Nitric acid, $H N O_{3}$ .

Important Questions on Atoms and Molecules

HARD

9th CBSE

IMPORTANT

SCIENCE TEXTBOOK FOR CLASS IX>Chapter 3 - Atoms and Molecules>Exercises>Q 7

What is the mass of
(a)

1

mole of nitrogen atoms?
(b)

4

moles of aluminium atoms (Atomic mass of aluminium

= 27

)?
(c)

10

moles of sodium sulphite

(N a_{2} S O_{3})

?

HARD

9th CBSE

IMPORTANT

SCIENCE TEXTBOOK FOR CLASS IX>Chapter 3 - Atoms and Molecules>Exercises>Q 8

Convert into mole.
(a)

12 g

of oxygen gas
(b)

20 g

of water
(c)

22 g

of carbon dioxide.

HARD

9th CBSE

IMPORTANT

SCIENCE TEXTBOOK FOR CLASS IX>Chapter 3 - Atoms and Molecules>Exercises>Q 9

What is the mass of:
(a)

0.2

mole of oxygen atoms?
(b)

0.5

mole of water molecules?

HARD

9th CBSE

IMPORTANT

SCIENCE TEXTBOOK FOR CLASS IX>Chapter 3 - Atoms and Molecules>Exercises>Q 10

Calculate the number of molecules of Sulphur

(S_{8})

present in

16 g

of solid sulphur (Avogadro number =

6.022 \times 10^{23}

).

HARD

9th CBSE

IMPORTANT

SCIENCE TEXTBOOK FOR CLASS IX>Chapter 3 - Atoms and Molecules>Exercises>Q 11

Calculate the number of aluminium ions present in

0.051 g

of aluminium oxide. (Take avogadro number as

6.022 \times 10^{23}

)
(Hint: The mass of an ion is the same as that of an atom of the same element. Atomic mass

Al = 27 u

)