Question

6. Explain the following terms with one example each.
(1) water of crystallization (ii) redox reaction (iii) olfactory indicators
(iv) neutralization reaction. (v) amphoteric oxides.

Answer 1

Water of Crystallisation

The hydrated salts consists some amount of water in them in crystallzed form which is termed as Water of Crystallisation. On burning, the hydrated salt looses water content and become anhydride salt.

Redox Reaction

The reaction where Oxidation and Reduction, both takes part simultaneously are called redox reaction.

Olfactory Indicators

The indicators that change their specific smelling characteristics with acid and base are termed olfactory indicators.

Neutralization Reaction

The reaction whete acid and base react to get neutralised is called neutralization reaction.

Amphoteric Oxides

The oxides which show both basic and acidic properties are termed as amphoteric oxides.

Answer 2

Explanation:-

1) Water of crystallization :-

It is defined as total number of water molecules attached to the molecules in their crystal structure.

There are certain compounds in which water molecules is attached to it. They are a part of internal structure of compound and cannot make crystal wet.

• Some of the compounds are :-

$Fe + H_2O \rightarrow Fe_2O_3.x H_2O$

$CuSO_4 . 5H_2O , FeSO_4.7H_2O$

where x is the number of water of crystallization attached.

Property → Water of crystallization gives the certain colours to the compounds.

2) Redox Reaction :-

The reaction in which there is oxidation and reduction of the elements or compounds taking place simultaneously is known as redox reaction.

In redox reaction there is always change in oxidation number.

Ex:-

$CuO + H_2\rightarrow 2Cu + H_2O$

3) Olfactory indicators:-

Those indicators (mainly natural) which change their smell in acidic or basic medium is called olfactory indicators.

Ex :-

Onion, vanilla, clove are some olfactory indicators.

4) Neutralization Reaction :-

The reaction in which an acids react with base and both neutralise their effect is known as neutralization reaction.

The products of neutralization reaction are :- Salt ( neutral compound) , water.

Reaction mechanism:-

$H^+ + OH^- \rightarrow H_2O$

$NaOH + HCl \rightarrow NaCl + H_2O$

5) Amphoteric oxides :-

Those oxides of metals which shows both the properties of acids and base is called Amphoteric oxides.

Ex :- $ZnO, Al_2O_3$

Reaction mechanism:-

$ZnO + HCl \rightarrow ZnCl_2 + H_2 O$

• here, ZnO shows the properties of base.

$NaOH + ZnO \rightarrow Na_2ZnO_2 + H_2 O$

• here, ZnO shows the properties of acids.