Explain the following:
(a) Same substance can act both as colloids and crystalloids.
(b) Artifical rain is caused by spraying salt over clouds.
(c) When a beam of light is passed through a colloidal sol, the path of the beam gets illuminated.

What is demulsification? Name two demulsifiers.

Explain the following terms:
(i) Electrophoresis
(ii) Coagulation
(iii) Dialysis                        
 (v) Tyndal effect

Write one difference in each of the following:
(i) Lyophobic sol and lyophilic sol.
(ii) Solution and colloid.
(iii) Homogeneous catalysis and heterogeneous catalysis

(i) In reference to Freundlich's adsorption isotherm, write the expression for adsorption of gases on solids in the form of an equation.
(ii) Write an important characteristic of lyophilic sols.
(iii) Based on the type of particles of dispersed phase, give one example each of associated colloid and multimolecular colloid.

What are the applications of adsorption in chemical analysis?

Radha and Meera are fast friends. They both study in class XII.Radha is a student of science while Meera follows commerce stream. One day, when they were playing, Radha got hurt and started bleeding. Meera took her to house and applied some alum on the cut. The bleeding stopped immediately.
(i)Why bleeding stopped when some alum is applied on the cut?
(ii) What are the values associated with Meera's decision to take Radha to her house and apply alum on her cut?

On visit to your native village, you find that lot of smoke, dust and some other gases are coming out of the chimney of a recently set up factory near the village.
(i) As a chemistry student, what method you will suggest the factory owner to manage dust and smoke?
(ii) What is the basic principle involved in your suggestion?
(iii) What values are associated with your advice?

Surface chemistry deals with phenomenon that occurs at all the surface or interfaces. Many important phenomenon- corrosion electrode process, heterogeneous catalysis, dissociation, adsorption, crystallisation occur at the interfaces.
Answer the following questions:
(i) Why do we use charcoal, in gas masks, in coal mines?
(ii) How is animal charcoal, used in the decolourisation of sugar?
(iii) What is the use of silica gel which is given alongwith camera and other electronic equipments?
(iv) There is safety lamp in coal mines. What is its purpose?

Hydrogenation of vegetable oil in presence of catalyst, is used to prepare vegetable ghee.
Vegetable oil ⟶ Vegetable ghee
It is the most important industrial process.
Answer the following questions:
(i) Which catalyst is commonly used in hydrogenation process and in which state?
(ii) Do you think we should use vegetable ghee instead of vegetable oils?
(iii) Is use of nickel useful or harmful for our body?
(iv) Why should we avoid taking deep fried snacks?
(v) Why should excessive use of antacids be avoided?

Shyam living in Shimla, was washing clothes in cold water. He found that the clothes were not getting clean. Sneha, his grandmother, suggested that he wash the clothes in warm water, Washing of clothes with soaps or detergents is easier in luke warm water than cold water.
Answer the following questions:
(i) Why is it easier to wash the clothes in luke warm water?
(ii) What values are associated with these information?

1 g of charcoal adsorbs 100 ml of 0.5 M CH₃COOH to form a monolayer, and thereby the molarity of CH₃ COOH reduces to 0.49 M. Calculate the surface area of the charcoal adsorbed by each molecule of acetic. Surface area of charcoal = \(3.01\times { 10 }^{ 2 }{ m }^{ 2 }g\)