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

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IMPORTANT

Earn 100

Write down the formula of magnesium hydroxide.

Important Questions on Atoms and Molecules

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9th CBSE

IMPORTANT

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

How many atoms are present in a
(i)

H_{2} S

molecule and
(ii)

{P O}_{4}^{3 -}

ion?

HARD

9th CBSE

IMPORTANT

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

Calculate the molecular masses of

H_{2}, O_{2}, C l_{2}, C O_{2}, C H_{4}, C_{2} H_{6}, C_{2} H_{4}, N H_{3}, C H_{3} O H

.

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IMPORTANT

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

Calculate the formula unit masses of

Z n O, N a_{2} O, K_{2} C O_{3},

given atomic masses of

Z n = 65 u, N a = 23 u, K = 39 u, C = 12 u,

and

O = 16 u .

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9th CBSE

IMPORTANT

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

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}

).

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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 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?

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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}

.