How do emulsifires stabilise emulsion? Name two emulsifiers.
The role of an emulsifier in stabilising an emulsion can be explained in two ways:
(a) It is believed that an emulsifier gets concentrated at the oil-water interface i.e., the surface at which oil and water come in contact with each other. It forms a protective coating around each drop of oil and thus, prevents the oil drop from coming in contact with one another. The oil drops remain suspended in water and are not coagulated.
(b) According to an another view, the role of the emulsifier is the sjame as that of lubricant in a machine. Just as a lubricant reduces the friction in the various parts of machine, an emulsifier also tries to reduce the interfacial tension between oil and water by suitable means. Thus, oil and water remain in company of each other and do not get separated. The commonly used emulsifying agents are soaps, detergents, lyophilic colloids, proteins, gums, gelatin, caesin, agar etc.
A colloid is formed by adding FeCl3 in excess of hot water. What will happen if excess sodium chloride is added to this colloid?
Assertion (A): Colloidal solutions show colligative properties.
Reason (R): Colloidal particles are large in size.
Explain what is observed
(i) when a beam of light is passed through a colloidal sol.
(ii) an electrolyte, NaCI is added to hydrated ferric oxide sol.
(iii) electric current is passed through a colloidal sol.
What type of solutions are formed on dissolving different concentrations of soap in water?
Why is it essential to wash the precipitate with water before estimating it quantitatively?
Distinguish between the meaning of the terms adsorption and absorption. Give one example of each.
Why does the white precipitate of silver halide become coloured in the presence of dye eosin.
What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated?
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the following choices:
(a) Both Assertion and Reason are correct and the Reason is the correct explanation for Assertion.
(b) Both Assertion and Reason arc correct but Reason is not the correct explanation for Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Both Assertion and Reason are incorrect.
(e) Assertion is incorrect but Reason is correct
Assertion (A): An ordinary filter paper impregnated with collodion solution stops the flow of colloidal particles.
Reason (R): Pore size of the filter paper becomes more than size of colloidal particle.
Method of formation of solution is given in Column I. Match it with the type of solution given in Column II.
Assertion (A): Colloidal solutions do not show Brownian motion.
Reason (R): Brownian motion is responsible for stability of sols.
Freundlich adsorption isotherm is given by the expression x/m=KP1/n. Which of the following conclusions can be drawn from this expression?
Which of the following phenomenon occurs when a chalk stick is dipped in ink?
(a) Adsorption of coloured substance
(b) Adsorption of solvent
(c) Absorption and adsorption both of solvent
(d) Absorption of solvent.
Match the types of colloidal systems given in Column I with the name given in Column II.
What is the role of adsorption in froth floatation process used especially for concentration of sulphide ores?
Assertion (A): Detergents with low CMC are more economical to use. Reason (R): Cleansing action of detergents involves the formation of micelles. These are formed when the concentration of detergents becomes equal to CMC.
Which of the following statements are correct about solid catalyst?
(a) Same reactants may give different product by using different catalysts.
(b) Catalyst does not change AH of reaction.
(c) Catalyst is required in large quantities to catalyse reactions.
(d) Catalytic activity of a solid catalyst does not depend upon the strength of chemisorption.
