Surface Chemistry Quiz-19

Surface Chemistry Quiz-19

Dear Readers,

The one subject in NEET which is candidates who can easily attain good marks is Chemistry. That's the reason, often, one doesn’t pay notice and choose to compromise it. But if one wants to rank above others, the tip is to be thorough with NEET chemistry concepts. The understanding of reactions and definite basic understanding is what requires major attention in Chemistry but once done it only gets simpler from there. The main focus on the to-do list should be on getting a hang of the NCERT syllabus of NEET chemistry. .

Q1.  Which of the following has maximum value of flocculating power?

•   Pb²⁺
•   Pb⁴⁺
•   Sr²⁺
•   Na⁺

Solution
The phenomenon of change of colloidal state to suspension state is called flocculation of colloidal solution.
According to Hardy-Schulze rule, the flocculating power of electrolyte increases with valency of ion of electrolyte.

Q2.  The decomposition of hydrogen peroxide can be slowed by the addition of acetamide. The latter acts as a

•   Detainer
•   Stopper
•   Promoter
•   Inhibitor

Solution
The decomposition of H₂O₂ can be slowed by the addition of acetamide. Acetamide act as an inhibitor.
Catalytic poisons or inhibitorare those substances which decrease or inhibit the activity of catalyst.

Q3.  Select wrong statement.

•   If a very small amount of AlCl₃is added to gold sol, coagulation occurs, but if a large quantity of AlCl₃is added, there is no coagulation.
•   Organic ions are more strongly adsorbed on charged surfaces in comparison to inorganic ions.
•   Both emulsifier and peptising agents stabilise colloids but their actions are different.
•   Colloidal solutions are thermodynamically stable.

Solution
The phenomenon of the precipitation of a colloidal solution by the addition of the excess of an electrolyte is called coagulation. When oppositely charged sols are mixed in almost equal proportions, their charges are neutralised. So, statement (a) is wrong.

Q4.  Surface tension of lyophilic sols is :

•   Lower than H₂O
•   More than H₂O
•   Equal to H₂O
•   None of these

Solution
Lyophilic sols have lower surface tension than H₂O due to loving nature towards H₂O.

Q5. The charge on As₂S₃sol is due to the adsorption of :

•   H⁺
•   OH^-
• 
•   S^2-

Solution
  —do—

Q6.  A liquid which markedly scatters a beam of light (visible in dark room) but leaves no residue when passed through a filter paper is best described as :

•   A suspension
•   Sol
• True solution
•   None of these

Solution
Sols or colloidal solutions scatter light and are passed through ordinary filter paper.

Q7. On adding few drops of dil HCl to freshly precipitated ferric hydroxide, a red coloured solution is obtained. This phenomenon is known as

•   Peptisation
•   Dialysis
•   Protective action
•   Dissolution

Solution
When a coagulated substance (ie, colloidal solution) is treated with a suitable electrolyte, it again changes to a colloidal solution, this is known as peptization

Q8. Which of the following is used to provide smoke screens :

•   Calcium phosphide
•   Zinc sulphate
•   Sodium carbonate
•   Zinc phosphide

Solution
Calcium phosphide reacts with moisture to give PH₃∙PH₃ reacts with O₂ to give white dense for of P₂O₅.

Q9. In Zeigler-Natta polymerisation of ethylene, the active species is :

•   AlCl₃
•   Et₃Al
•   CH₂CH₂
•   Ti^III

Solution
Zeigler-Natta catalyst is formed by the action of (C₂H₅)₃Al and TiCl₄. The active species is Ti^III as (C₂H₅)₃Al can reduce TiCl₄ to TiCl₃.Ti^III has one active site vacant and thus accommodates one alkyl group.

Q10.  When adsorption of oxalic acid is carried out on activated charcoal, the activated charcoal is known as

•   Adsorbate
•   Adsorbent
•   Adsorber
•   All of these

Solution
Adsorbent is the surface on which adsorption occurs