SCIENCE TEXTBOOK FOR CLASS IX>Chapter 3 - Atoms and Molecules>Exercises>Q 1

HARD

9th CBSE

IMPORTANT

Earn 100

A $0.24 g$ sample of compound of oxygen and boron was found by analysis to contain $0.096 g$ of boron and $0.144 g$ of oxygen. Calculate the percentage composition of the compound by weight.

Important Questions on Atoms and Molecules

HARD

9th CBSE

IMPORTANT

SCIENCE TEXTBOOK FOR CLASS IX>Chapter 3 - Atoms and Molecules>Exercises>Q 2

When

3.0 g

of carbon is burnt in

8.00 g

oxygen,

11.00 g

of carbon dioxide is produced. What mass of carbon dioxide will be formed when

3.00 g

of carbon is burnt in

50.00 g

of oxygen? Which law of chemical combination will govern your answer?

EASY

9th CBSE

IMPORTANT

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

What are polyatomic ions? Give examples.

HARD

9th CBSE

IMPORTANT

SCIENCE TEXTBOOK FOR CLASS IX>Chapter 3 - Atoms and Molecules>Exercises>Q 4

Write the chemical formulae of the following:
(a) Magnesium chloride
(b) Calcium oxide
(c) Copper nitrate
(d) Aluminium chloride
(e) Calcium carbonate.

MEDIUM

9th CBSE

IMPORTANT

SCIENCE TEXTBOOK FOR CLASS IX>Chapter 3 - Atoms and Molecules>Exercises>Q 5

Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.

MEDIUM

9th CBSE

IMPORTANT

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

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}

.

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?