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141.
Presence of traces of arsenious oxide $$\left( {A{s_2}{O_3}} \right)$$ in the reacting gases $$S{O_2}$$ and $${O_2}$$ in presence of platinised asbestos in contact process acts as
A
catalytic promoter
B
catalytic poison
C
dehydrating agent
D
drying agent
Answer :
catalytic poison
The presence of traces of $${A{s_2}{O_3}}$$ in the reacting gases reduces the activity of platinised asbestos which is used as catalyst in contact process.
142.
In Freundlich adsorption isotherm, the value of $$\frac{1}{n}$$ is :
A
between 0 and 1 in all cases
B
between 2 and 4 in all cases
C
1 in case of physical adsorption
D
1 in case of chemisorption
Answer :
between 0 and 1 in all cases
According to Freundlich adsorption isotherm
$$\frac{x}{m} = k{p^{\frac{1}{n}}}$$
at low pressure, $$\frac{1}{n} = 1$$
$$\therefore \,\,\frac{x}{m} \propto {p^1}$$
at high pressure, $$\frac{1}{n} = 0$$
$$\frac{x}{m} \propto {p^ \circ }$$
i.e., the value of $$n$$ varies between 0 to 1
143.
The gold numbers of protective colloids $$A, B, C$$ and $$D$$ are 0.04, 0.004, 10 and 40 respectively. The protective powers of $$A, B, C$$ and $$D$$ are in the order :
A
$$A > B > C > D$$
B
$$B > A > C > D$$
C
$$D > C > A > B$$
D
$$D > C > B > A$$
Answer :
$$B > A > C > D$$
Smaller is the 'gold number' of protective colloid, greater is its protective power.
144.
The adsorption of a gas on a solid surface varies with pressure of the gas in which of the following
manner.
A
Fast → slow → independent of the pressure
B
Slow → fast → independent of the pressure
C
Independent of the pressure → fast → slow
D
Independent of the pressure → slow → fast
Answer :
Fast → slow → independent of the pressure
Adsorption of a gas on solid is represented by following equilibria,
Gas (Adsorbate) + Solid (Adsorbent) $$ \rightleftharpoons $$ Gas adsorbed on solid + Heat
Initially adsorption increases with increase in pressure at a particular temperature then got slow. After attaining equilibrium, adsorption becomes independent of pressure.
145.
Methylene blue, from its aqueous solution, is adsorbed on activated charcoal at $${25^ \circ }C.$$ For this process, which of the following statement is correct ?
A
The adsorption requires activation at $${25^ \circ }C$$
B
The adsorption is accompanied by a decrease in enthalpy
C
The adsorption increases with increase of temperature
D
The adsorption is irreversible
Answer :
The adsorption is accompanied by a decrease in enthalpy
The adsorption of methylene blue on activated charcoal is an example of physiosorption which is exothermic, multilayer and does not have energy barrier.
146.
According to Langmuir adsorption isotherm, the amount of gas adsorbed at very high pressures
A
reaches a constant limiting value
B
goes on increasing with pressure
C
goes on decreasing with pressure
D
increases first and then decreases with pressure
Answer :
reaches a constant limiting value
According to Langmuir adsorption isotherm, the amount of gas adsorbed at very high pressure reaches a constant limiting volume.
147.
Which of the following statements is correct for Tyndall effect?
A
Scattering and polarizing of light by small suspended particles is called Tyndall effect.
B
Tyndall effect of colloidal particles is due to dispersion of light.
C
Tyndall effect is due to refraction of light.
D
Zig-zag motion of suspended particles.
Answer :
Scattering and polarizing of light by small suspended particles is called Tyndall effect.
Tyndall effect is scattering of light by colloidal particles.
148.
Among the electrolytes $$N{a_2}S{O_4},$$ $$CaC{l_2},$$ $$A{l_2}{\left( {S{O_4}} \right)_3}$$ and $$N{H_4}Cl,$$ the most effective coagulating agent for $$S{b_2}{S_3}$$ sol is
A
$$N{a_2}S{O_4}$$
B
$$CaC{l_2}$$
C
$$A{l_2}{\left( {S{O_4}} \right)_3}$$
D
$$N{H_4}Cl$$
Answer :
$$A{l_2}{\left( {S{O_4}} \right)_3}$$
As $$S{b_2}{S_3}$$ is a negative sol, so $$A{l_2}{\left( {S{O_4}} \right)_3}$$ will be the most effective coagulant due to higher positive charge on $$Al\left( {A{l^{3 + }}} \right) - $$ Hardy-Schulze rule.
149.
Which of the following is not characteristic of chemisorption?
A
Adsorption is specific.
B
Heat of adsorption is of the order of $$200\,kJ\,mo{l^{ - 1}}.$$
C
Adsorption is irreversible.
D
Adsorption may be multimolecular layers.
Answer :
Adsorption may be multimolecular layers.
Chemisorption forms unimolecular or one layer.
150.
If a beam of light is passed through true solution, then it is
A
visible
B
scatter
C
not visible
D
None of the above
Answer :
not visible
When a beam of light is passed through true solution, then the path of light is invisible due to fact that the size of particles in true solution is below $$1$$ $$nm,$$ so they cannot scatter the light that means cannot show Tyndall effect.