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
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 :
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 :
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
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
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 $$200\,kJ\,mo{l^{ - 1}}.$$
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.