Why the sun looks red at the time of setting ? Explain on the basis of colloidal properties.

2

(a)

Addition of H₂ to acetylene gives ethane in presence of palladium but if BaSO₄ and quinoline or sulphur are also added, the product is ethane. Why ?

2

(a)

SnO₂ forms a positively charged colloidal sol in acetic medium and a negatively charged sol in the basic medium. Why ? Explain.

2

(a)

Explain the following giving reasons :
(i) Rate of physical adsorption decreases with rise of temperature.
(ii) Cause Brownian movement.
(iii) Colloidal particles scatter light. 

2

(a)

How does the rate of enzyme - catalysed reactions vary with (i) temperarture (ii) pH ? Represent diagrammatically.

2

(a)