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181.
Few reactions of industrial importance are listed below. Which of the following catalysts is not correctly matched with the reaction ?
A
Haber's process : Finely divided $$Fe + Mo$$ as promoter
B
Contact process : $${V_2}{O_5}$$
C
Ostwald's process : $$F{e_2}{O_3}$$
D
None of these.
Answer :
Ostwald's process : $$F{e_2}{O_3}$$
Platinised asbestos is used as a catalyst for Ostwald's process for the manufacture of nitric acid.
182.
Flocculation value of $$BaC{l_2}$$ is much less than that of $$KCl$$ for sol $$A$$ and flocculation value of $$N{a_2}S{O_4}$$ is much less than that of $$NaBr$$ for sol $$B.$$ The correct statement among the following is :
A
Both the sols $$A$$ and $$B$$ are negatively charged.
B
Sol $$A$$ is positively charged and Sol $$B$$ is negatively charged.
C
Both the sols $$A$$ and $$B$$ are positively charged.
D
Sol $$A$$ is negatively charged and sol $$B$$ is positively charged.
Answer :
Sol $$A$$ is positively charged and Sol $$B$$ is negatively charged.
In first case the given compounds have same anion but different cations having different charge hence they will precipitate negatively charged sol i.e.$$'A'.$$
In second case the given compounds have similar cation but different anion with different charge. Hence they will precipitate positively charged sol. i.e. $$'B'.$$
183.
Among the following, correct statement is :
A
Brownian movement is more pronounced for smaller particles than for bigger–
particles.
B
Sols of metal sulphides are lyophilic.
C
Hardy Schulze law states that bigger the size of the ons, the greater is its coagulating
power.
D
One would expect charcoal to adsorb chlorine more than hydrogen sulphide.
Answer :
Brownian movement is more pronounced for smaller particles than for bigger–
particles.
Brownian movement is the random motion of particles suspended in a fluid ( a liquid or gas ) resulting from their collision with the fast moving atom or molecules in the liquid or gaseous state of the matter. That means smaller particles are responsible for the Brownian movement than for bigger particles.
184.
Arrange the following electrolytes in the increasing order of coagulating power for ferric hydroxide sol
$$\mathop {N{a_3}P{O_4}}\limits_I \,\,\,\,\,\,\mathop {KCl\,\,}\limits_{II} \,\,\,\,\,\,\,\mathop {{K_2}S{O_4}\,}\limits_{III} \,\,\,\,\,\,\,\mathop {NaCl}\limits_{IV} $$
A
$$I < II < III < IV$$
B
$$II = IV < III < I$$
C
$$II = IV < I < III$$
D
$$II = III < IV = I$$
Answer :
$$II = IV < III < I$$
Ferric hydroxide sol is positively charged and hence anions would be effective in causing coagulation. Greater the valence of the effective ion, more will be its coagulating power.
185.
Powdered substances are more effective adsorbents than their crystalline form because
A
adsorption is an exothermic process
B
they become inert and do not react with the adsorbate
C
the extent of adsorption increases with increase in surface area of the adsorbent
D
adsorption is more if the size of adsorbent is small.
Answer :
the extent of adsorption increases with increase in surface area of the adsorbent
Finely powdered substances have large, porous surface areas, hence act as better adsorbent.
186.
Traces of molybdenum are used with finely divided iron which acts as a catalyst during Haber's process for synthesis of ammonia. The $$Mo$$
A
acts as a promoter to increase the activity of the catalyst
B
acts as a poison to decrease the activity of the catalyst
C
provides a new pathway to the reaction
D
forms another intermediate compound with lesser activation energy.
Answer :
acts as a promoter to increase the activity of the catalyst
Substances which themselves are not catalysts but when mixed in small quantities with the catalysts increase their efficiency are called promoters or activators
187.
Select incorrect statement :
A
Soap and detergent lower the interfacial surface tension between oil and water
B
Basic principle of peptization is reverse of coagulation
C
Soap and detergent used as emulsifiers
D
Lyophilic sols need stabilizing agent
Answer :
Lyophilic sols need stabilizing agent
No stabilising agent required for the preparation of lyophilic sol.
188.
Which of the following gases present in a polluted area will be adsorbed most easily on the charcoal gas mask ?
A
$${H_2}$$
B
$${O_2}$$
C
$${N_2}$$
D
$$S{O_2}$$
Answer :
$$S{O_2}$$
Easily liquefiable gases like $$C{O_2},N{H_3},S{O_2},$$ etc. are more easily adsorbed than the elemental gases like $${H_2},{N_2},{O_2},$$ etc.
189.
The following statements relate to the adsorption of gases on a solid surface. Identify the incorrect statement among them :
A
Enthalpy of adsorption is negative
B
Energy appears as heat
C
On adsorption, the residual forces on the surface are increased
D
Entropy of adsorption is negative
Answer :
On adsorption, the residual forces on the surface are increased
Adsorption is a phenomena of attracting and retaining the molecules of a substance on the surface of a liquid or a solid resulting into a higher concentration of the molecules on the surface.
After adsorption there is a decrease in the residual forces due to bond formation $$\Delta G,\Delta H\,\& \,\Delta S$$ all are negative in the case of adsorption.
190.
Which of the following process is responsible for the formation of delta at a place where rivers meet the sea?
A
Emulsification
B
Colloid formation
C
Coagulation
D
Peptisation
Answer :
Coagulation
The process of accumulation of colloidal particles together to get the size which ultimately settles as a precipitate is called coagulation. It generally occurs in presence of an electrolyte. Coagulation of soil particles of river in presence of salts present in sea water is responsible for the formation of delta.