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21.
Movement of dispersion medium under the influence of electric field is known as
A
electrodialysis
B
electrophoresis
C
electroosmosis
D
cataphoresis
Answer :
electroosmosis
When movement of particles ( electrophoresis ) is prevented by some suitable means, it is observed that the dispersion medium begins to move in an electric field. This phenomenon is termed as electroosmosis.
22.
Which of the following gases is least adsorbed on charcoal ?
A
$$HCl$$
B
$$N{H_3}$$
C
$${O_2}$$
D
$$C{O_2}$$
Answer :
$${O_2}$$
It has been found that more readily liquefiable gases are adsorbed more than permanent gases.
23.
Lyophilic sols are
A
Irreversible sols
B
They are prepared from inorganic compound
C
Coagulated by adding electrolytes
D
Self-stabilizing
Answer :
Self-stabilizing
Lyophilic sols are self stabilizing because these sols are reversible and are highly hydrated in the solution.
24.
Which one of the following statements is incorrect about enzyme catalysis?
A
Enzymes are mostly proteinous in nature
B
Enzyme action is specific
C
Enzymes are denaturated by $$UV$$ - rays and at high temperature
D
Enzymes are least reactive at optimum temperature
Answer :
Enzymes are least reactive at optimum temperature
Most of the enzymes have proteinous nature. They are highly specific and get denaturated by high temperature or $$UV$$ - rays. At optimum temperature, which is generally in between $${25^ \circ } - {35^ \circ }C,$$ enzyme activity is maximum.
25.
Which of the following processes does not occur at the interface of phases?
A
Crystallisation
B
Heterogeneous catalysis
C
Homogeneous catalysis
D
Corrosion
Answer :
Homogeneous catalysis
In homogeneous catalysis, the reactants and the catalyst are in the same phase. Thus, there is no interface in homogeneous catalysis.
26.
Aluminium hydroxide forms a positively charged sol. Which of the following ionic substances
should be most effective in coagulating the sol?
A
$$NaCl$$
B
$$CaC{l_2}$$
C
$$F{e_2}{\left( {S{O_4}} \right)_3}$$
D
$${K_3}P{O_4}$$
Answer :
$${K_3}P{O_4}$$
$$Al{\left( {OH} \right)_3}$$ is positively charged sol. $${K_3}P{O_4}$$ has greater negative charge. Hence, it is most effective in coagulation
27.
Which of the following electrolytes will have maximum coagulating value for $$AgI/A{g^ + }$$ sol?
A
$$N{a_2}S$$
B
$$N{a_3}P{O_4}$$
C
$$N{a_2}S{O_4}$$
D
$$NaCl$$
Answer :
$$N{a_3}P{O_4}$$
$$AgI/A{g^ + }$$ is positive colloid, it will be coagulated easily by the anion with large negative charge i.e., $$PO_4^{3 - }.$$
28.
Which of the following statements regarding difference between adsorption and absorption is incorrect ?
A
Adsorption is a surface whereas absorption is a bulk phenomena.
B
Water vapours are absorbed by anhydrous $$CaC{l_2}$$ but adsorbed by silica gel.
C
Adsorption and absorption take place individually. They can not occur simultaneously.
D
All of the above statements are correct.
Answer :
Adsorption and absorption take place individually. They can not occur simultaneously.
Both adsorption and absorption can take place simultaneously. The term sorption is
used to describe both the processes.
29.
Which of the following statements is correct about solid catalysts ?
A
Catalyst is required in equal amount as the reactants present in the reaction.
B
Catalytic activity of a solid catalyst does not depend upon the extent of chemisorption.
C
Desorption is not important for a solid to act as good catalyst.
D
Same reactants may give different products by using different catalysts.
Answer :
Same reactants may give different products by using different catalysts.
A catalyst is specific nature. Same reactants can give different products with different catalysts.
30.
In Langmuir's model of adsorption of a gas on a solid surface
A
the mass of gas striking a given area of surface is proportional to the pressure of the gas
B
the mass of gas striking a given area of surface is independent of the pressure of the gas
C
the rate of dissociation of adsorbed molecules from the surface does not depend on the surface covered
D
the adsorption at a single site on the surface may involve multiple molecules at the same time.
Answer :
the mass of gas striking a given area of surface is proportional to the pressure of the gas
According to Langmuir's model of adsorption of a gas on a solid surface, the mass of gas adsorbed $$(x)$$ per gram of the adsorbent $$(m)$$ is directly proportional to the pressure of the gas $$(p)$$ at constant temperature.