Why does leather get hardened after tanning?
Animal skin is colloidal, in nature and carries positive charge. Tannin is a negatively charged colloidal solution. When leather is soaked in tannin, mutual coagulation of the two takes place and leather gets hardened.
Why is it essential to wash the precipitate with water before estimating it quantitatively?
A colloid is formed by adding FeCl3 in excess of hot water. What will happen if excess sodium chloride is added to this colloid?
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.
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.
What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated?
Freundlich adsorption isotherm is given by the expression x/m=KP1/n. Which of the following conclusions can be drawn from this expression?
H2 gas is adsorbed on activated charcoal to a very little extent in comparison
to easily liquefiable gases due to
(a) very strong van der Waals interaction
(b) very weak van der Waals forces
(c) very low critical temperature
(d) very high critical temperature.
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.
Which of the following substances will precipitate the negatively charged emulsions?
(a) KCl (b) Glucose
(c) Urea (d) NaCl
Give an example where physisorption changes to chemisorption with rise in temperature. Explain the reason for change.
What is the role of adsorption in froth floatation process used especially for concentration of sulphide ores?
How does it become possible to cause artificial rain by spraying silver iodide on the clouds?
Method of formation of solution is given in Column I. Match it with the type of solution given in Column II.
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.
Why does the white precipitate of silver halide become coloured in the presence of dye eosin.
Assertion (A): Colloidal solutions show colligative properties.
Reason (R): Colloidal particles are large in size.
Which phenomenon occurs when an electric field is applied to a-colloidal solution and electrophoresis is prevented?
(a) Reverse osmosis takes place.
(b) Electroosmosis takes place.
(c) Dispersion medium begins to move.
(d) Dispersion medium becomes stationary.
Assertion (A): Colloidal solutions do not show Brownian motion.
Reason (R): Brownian motion is responsible for stability of sols.
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.
What type of solutions are formed on dissolving different concentrations of soap in water?
Which of the following options are correct?
(a) Micelle formation by soap in aqueous solution is possible at all temperatures.
(b) Micelle formation by soap in aqueous solution occurs above a particular concentration.
(c) On dilution of soap solution micelles may revert to individual ions.
(d) Soap solution behaves as a normal strong electrolyte at all concentrations.
Which of the following statements are correct?
(a) Mixing two oppositely charged sols neutralizes their charges and stabilizes the colloid.
(b) Presence of equal and similar charges on colloidal particles provides stability to the colloids.
(c) Any amount of dispersed liquid can be added to emulsion without destabilizing it.
(d) Brownian movement stabilizes sols.
Which of the following colloids cannot be coagulated easily?
(a) Lyophobic colloids (b) Irreversible colloids
(c) Reversible colloids (d) Lyophilic colloids
