Class 12th

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans:  (i) and (ii)

Substances which accelerate the rate of a chemical reaction and themselves remain chemically and quantitatively unchanged after the reaction, are known as catalysts they can undergo physical change so the answers are (i) and (ii).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans:  (ii) and (iii).

When electrophoresis, i.e, movement of particles is prevented by some suitable means, it is observed that the dispersion medium begins to move in an electric field. This phenomenon is termed electroosmosis so the answers are (ii) and (iii).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans:  (i) and  (iii)

Lyophilic colloids have a unique property of protecting lyophobic colloids. When a lyophilic sol is added to the lyophobicm sol, the lyophilic particles form a layer around lyophobic particles and thus protect the latter from electrolytes. Lyophilic colloids used for this purpose are called protective colloid so the answers are (i) and  (iii).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans:  (iii)  and  (iv)

Sols  directly  formed  by mixing substances  like  gum, gelatin,   starch, rubber, etc., with a  suitable liquid (the  dispersion 

medium) are  called lyophilic sols. They are  also known as  reversible colloid.  These sols  are  very stable  and cannot

coagulate easily hence the answers are (iii)  and  (iv).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans: (i) and  (iv)

Negatively charged emulsion can  be  precipitated by oppositely  charged electrolyte. Na+ and K+ from the  electrolyte can  neutralize  the  negatively  charge  emulsion and  precipitate  the  colloid so the answers are (i) and  (iv).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans: (ii) and (iv)

Emulsions can be broken into constituent liquids by heating, freezing and centrifuging hence the answer is (ii) and (iv).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans:  (ii) and (iv)

The presence of equal and similar charges on colloidal particles is largely responsible in providing stability to the colloidal

solution, because the repulsive forces between charged particles having same charge prevent them from coalescing or

aggregating when they come closer to one another. The Brownian movement has stirring effect which does not permit the particles to settle and thus, is responsible for the stability of sols hence the answer is (ii) and (iv).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans:   (ii) and (iii)

H₂ molecule on an activated charcoal is adsorbed to a very little extent in comparison to easily liquefiable gases because it has (a) Very weak van there Waals force of attraction (b) Very low critical temperature hence the answer is (ii) and (iii).

This is a Multiple Choice Type Questions as classified in NCERT Exemplar

Ans: (i) and (iii)

Freundlich gave an empirical relationship between the quantity of gas adsorbed by unit mass of solid adsorbed and pressure at a particular temperature.

$\frac{\mathrm{x}}{\mathrm{p}}$ =kp $\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$\mathrm{n}$}\right.$

If $\frac{1}{\mathrm{n}}$  = 0 ; $\frac{\mathrm{x}}{\mathrm{m}}$  = k xtent of adsorption is independent of pressure

When n=0 ; $\frac{\mathrm{x}}{\mathrm{m}}$  = kp

$\frac{\mathrm{x}}{\mathrm{m}}$  vs p is a line

parallel to x-axis