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

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IMPORTANT

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Write down the formula of magnesium hydroxide.

Important Questions on Atoms and Molecules

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IMPORTANT

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

Write down the names of compounds represented by the following formulae:
(i)

A l_{2} {(S O_{4})}_{3}

(ii)

C a C l_{2}

(iii)

K_{2} S O_{4}

(iv)

K N O_{3}

(v)

C a C O_{3}

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

What is meant by the term chemical formula?

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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?

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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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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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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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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}

)?

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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.