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Surface Chemistry · Question 22

AIPMT 2005MCQEasy📈 Topic in 25% papers+4−1
1

Which one of the following forms micelles in aqueous solution above certain concentration?

  1. Dodecyl trimethyl ammonium chloride
  2. Glucose
  3. Urea
  4. Pyridinium chloride

Answer

(1) Dodecyl trimethyl ammonium chloride

Solution

As per NCERT, micelles are formed by surface-active agents (soaps and detergents) above the critical micelle concentration (CMC); such molecules have a long hydrophobic hydrocarbon tail and a polar (ionic) head.

Dodecyl trimethyl ammonium chloride, CH3(CH2)11N (CH3)3 Cl , is a cationic detergent: C12 hydrophobic tail + ionic head. ⇒ It forms micelles.

Glucose and urea are non-ionic small molecules, and pyridinium chloride has no long hydrocarbon tail. ⇒ They cannot form micelles.

Answer: (1)

Out of syllabusAIPMT 2005

Keep practising — Surface Chemistry

2

Which of the following forms cationic micelles above certain concentration?

  1. Sodium dodecyl sulphate
  2. Sodium acetate
  3. Urea
  4. Cetyltrimethylammonium bromide.
Out of syllabusAIPMT 2004
3

According to the adsorption theory of catalysis, the speed of the reaction increases because

  1. the concentration of reactant molecules at the active centres of the catalyst becomes high due to adsorption
  2. in the process of adsorption, the activation energy of the molecules becomes large
  3. adsorption produces heat which increases the speed of the reaction
  4. adsorption lowers the activation energy of the reaction.
Out of syllabusAIPMT 2003
4

Position of non-polar and polar part in micelle

  1. polar at outer surface but non-polar at inner surface
  2. polar at inner surface but non-polar at outer surface
  3. distributed over all the surface
  4. are present in the surface only
Out of syllabusAIPMT 2002
5

Which is not correct regarding the adsorption of a gas on surface of a solid?

  1. On increasing temperature adsorption increases continuously.
  2. Enthalpy and entropy change is negative.
  3. Adsorption is more for some specific substance.
  4. It is a reversible reaction.
Out of syllabusAIPMT 2001
6

Which one of the following methods is commonly used for the destruction of a colloid?

  1. Dialysis
  2. Condensation
  3. Filtration by animal membrane
  4. By adding electrolyte
Out of syllabusAIPMT 2000

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