Balance the following reactions. A l + O 2 → A l 2 O 3

An equation in which the number of atoms of the elements of reactants and products are equal is called a balanced equation. Aluminium reacts with oxygen to form aluminium oxide. 4 Al s + 3 O 2 g → 2 Al 2 O 3 s

Balance the following reactions. A l + O 2 → A l 2 O 3

An equation in which the number of atoms of the elements of reactants and products are equal is called a balanced equation. Aluminium reacts with oxygen to form aluminium oxide. 4 Al s + 3 O 2 g → 2 Al 2 O 3 s

Balance the following reactions. C a C O 3 + H Cl → C a C l 2 + H 2 O + C O 2

An equation in which the number of atoms of the elements of reactants and products are equal is called a balanced equation. Calcium carbonate reacts with hydrochloric acid to form aqueous calcium chloride and carbon dioxide. C a C O 3 s + 2 H Cl aq → C a C l 2 aq + H 2 O + C O 2 g

E M B I B E

Expanded Universal Science 7>Chapter 5 - Matter and Chemical Formulae>ASSESSMENT ZONE>Q F

HARD

7th CBSE

IMPORTANT

Earn 100

Balance the following reactions.
$A l + O_{2} \to {A l}_{2} O_{3}$

Important Questions on Matter and Chemical Formulae

HARD

7th CBSE

IMPORTANT

Expanded Universal Science 7>Chapter 5 - Matter and Chemical Formulae>ASSESSMENT ZONE>Q F

Balance the following reactions.

C a C O_{3} + H Cl \to C a C l_{2} + H_{2} O + C O_{2}

MEDIUM

7th CBSE

IMPORTANT

Expanded Universal Science 7>Chapter 5 - Matter and Chemical Formulae>ASSESSMENT ZONE>Q F

A dish contains a blackish-yellow powder. When a magnet is moved over it, black particles (iron) get stuck to the magnet, and only a yellow powder, which is sulphur, is left behind. Was your original powder an element, compound or mixture?

HARD

7th CBSE

IMPORTANT

Expanded Universal Science 7>Chapter 5 - Matter and Chemical Formulae>ASSESSMENT ZONE>Q F

If the valency of oxygen is

2

, derive the valency of the other elements present in the following oxides:
Sodium oxide

({N a}_{2} O),

Zinc oxide

(Z n O),

Lead oxide

(P b O)

, Aluminium oxide

{(A l}_{2} O_{3}),

Calcium oxide

(C a O),

Barium oxide

(BaO)

, Copper (II) oxide

(CuO)

.

MEDIUM

7th CBSE

IMPORTANT

Expanded Universal Science 7>Chapter 5 - Matter and Chemical Formulae>ASSESSMENT ZONE>Q F

Name the elements present in the following compound and write their valency.
Copper (II) hydroxide

MEDIUM

7th CBSE

IMPORTANT

Expanded Universal Science 7>Chapter 5 - Matter and Chemical Formulae>ASSESSMENT ZONE>Q F

Name the elements present in the following compound and write their valency.
Sulphur dioxide

MEDIUM

7th CBSE

IMPORTANT

Expanded Universal Science 7>Chapter 5 - Matter and Chemical Formulae>ASSESSMENT ZONE>Q F

A substance when viewed under an electron microscope revealed that it contains only one kind of atoms. Is the substance an element, compound or mixture?