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

MEDIUM

9th CBSE

IMPORTANT

Earn 100

If one mole of carbon atoms weighs $12$ gram, what is the mass (in grams) of $1$ atom of carbon? (Avogadro number $= 6.022 \times 10^{23}$ ).

Important Questions on Atoms and Molecules

MEDIUM

9th CBSE

IMPORTANT

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

Which has more number of atoms,

100

grams of sodium or

100

grams of iron (Given, atomic mass of

N a = 23 u, F e = 56 u

, Avogadro number

= 6.022 \times 10^{23}

)?

HARD

9th CBSE

IMPORTANT

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

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.

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})

?