What do you understand by shape selective catalysis? Why are zeolites good shape selective catalysts?
The catalytic reaction which depends upon the pore structure of the catalyst and the size of the reactant and product molecules is called shape selective catalysis. Zeolites are good shape selective catalysts because of their honey comb like structures.
(i) Zeolites are microporous aluminosilicates of the general formula Mx/n[(AlO2)x(SiO2)y]mH2O
(ii) Zeolites have an enormous surface area which is largely on the inside of the solid. The zeolites can permit the entry and exit of molecules of a certain size into the active regions within the holes.
(iii) They are used in petrochemical industries for cracking of hydrocarbons and isomerization.
(iv) The reactions in zeolites depend upon the size of the cavities (cages) and pores (tunnels) present in them. The pore size in zeolites generally varies between 260 pm and 740 pm.
(v) Zeolite catalyst known as ZSM-5 converts alcohols to gasoline. The alcohol is dehydrated in the cavities and the hydrocarbons are formed.
Assertion (A): Colloidal solutions show colligative properties.
Reason (R): Colloidal particles are large in size.
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.
What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated?
Why does the white precipitate of silver halide become coloured in the presence of dye eosin.
Distinguish between the meaning of the terms adsorption and absorption. Give one example of each.
What type of solutions are formed on dissolving different concentrations of soap in water?
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 do not show Brownian motion.
Reason (R): Brownian motion is responsible for stability of sols.
What is the role of adsorption in froth floatation process used especially for concentration of sulphide ores?
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.
Give an example where physisorption changes to chemisorption with rise in temperature. Explain the reason for change.
Match the types of colloidal systems given in Column I with the name given in Column II.
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.
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).
In Haber's process, hydrogen is obtained by reacting methane with steam in presence of NiO as catalyst. The process is known as steam reforming. Why is it necessary to remove CO when ammonia is obtained by Haber's process?
Do the vital functions of the body such as digestion get affected during fever? Explain your answer.
