What are the applications of adsorption in chemical analysis?
Adsorption has the following applications in chemical analysis:
(i) In qualitative analysis: Certain qualitative tests such as the lake test for the confirmation of Al3+ ions are based upon adsorption, i.e., Al(OH)3 has the capacity to adsorb the colour of blue litmus from the solution.
(ii) In adsorption indicators: Many adsorption indicators are being used in volumetric analysis e.g., dyes such as eosin and fluorescein are used as adsorption indicators. In these methods, the dyes are adsorbed on the surfaces of certain precipitates (such as silver halides) which give characteristic colour at the end point.
(iii) In ion-exchange resins: The organic polymers containing groups like -COOH, -SO3H and -NH2, etc. possess the property of selective adsorption of ions from solutions. These are quite useful in the softening of water.
(iv) Separation of inert gases: Due to the difference in degree of adsorption of gases by charcoal, a mixture of noble gases can be separated by adsorption on coconut charcoal at different temperatures.
(v) In froth floatation process: A low grade sulphide ore is concentrated by separating it from silica and other earthly matter by adsorption using pine oil and frothing agent.
(vi) Chromatographic analysis: The chromatographic technique for purification used in analytical and industrial fields is based on the phenomenon of adsorption.
Why is it essential to wash the precipitate with water before estimating it quantitatively?
What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated?
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.
A colloid is formed by adding FeCl3 in excess of hot water. What will happen if excess sodium chloride is added to this colloid?
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.
Assertion (A): Colloidal solutions show colligative properties.
Reason (R): Colloidal particles are large in size.
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.
Match the types of colloidal systems given in Column I with the name given in Column II.
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 do you understand by shape selective catalysis? Why are zeolites good shape selective catalysts?
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.
Freundlich adsorption isotherm is given by the expression x/m=KP1/n. Which of the following conclusions can be drawn from this expression?
In a reaction, catalyst changes
(a) physically (b) qualitatively
(c) chemically (d) quantitatively
Why does the white precipitate of silver halide become coloured in the presence of dye eosin.
Method of formation of solution is given in Column I. Match it with the type of solution given in Column II.
What is the role of adsorption in froth floatation process used especially for concentration of sulphide ores?
Distinguish between the meaning of the terms adsorption and absorption. Give one example of each.
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.
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.
An emulsion cannot be broken by and
(a) heating
(b) adding more amount of dispersion medium
(c) freezing
(d) adding emulsifying agent
Which of the following colloids cannot be coagulated easily?
(a) Lyophobic colloids (b) Irreversible colloids
(c) Reversible colloids (d) Lyophilic colloids
How does it become possible to cause artificial rain by spraying silver iodide on the clouds?
Assertion (A): Coagulation power of Al3+ is more than Na+
Reason (R): Greater the Valency of the flocculating ion added, greater is its power to cause precipitation (Hardy-Schulze rule).
