Q4 of 22 Page 45

Give scientific reasons.

It is reccommended to use air tight container for storing oil for long time.

It is recommended to use air tight container for storing oil for long time because:


⇒ When oil comes in contact with air, it undergoes air oxidation.


⇒ This can make the oil rancid (a foul smell).


⇒ Thus, it is advised to use air tight container for storing oil to prevent it from exposure of air.


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4

Give scientific reasons.

It takes time for pieces of Shahabad tile to disappear in HCl, but its powder disappears rapidly.

 4

Give scientific reasons.

While preparing dilute sulphuric acid from concentrated sulphuric acid in the laboratory, the concentrated sulphuric acid is added slowly to water with constant stirring.

 5

Observe the following picture a write down the chemical reaction with explanation.

 6

Identify from the following reactions the reactants that undergo oxidation and reduction.

a. Fe + S → FeS


b. 2Ag2O → 4 Ag + O2


c. 2Mg + O2→ 2MgO


d. NiO + H2→ Ni + H2O