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Surface Chemistry · Question 24

AIPMT 2003MCQMedium📈 Topic in 12% papers+4−1
1

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.

Answer

(4) adsorption lowers the activation energy of the reaction.

Solution

As per NCERT, the modern adsorption theory is a combination of the intermediate compound formation theory and the old adsorption theory: the reactants are adsorbed on the catalyst surface, react there through formation of an intermediate, and the products then desorb.

⇒ This surface path has a lower energy barrier; as per NCERT, a catalyst provides an alternate pathway that reduces the activation energy between reactants and products.

∴ Adsorption lowers the activation energy of the reaction, so the speed increases.

Note: the higher concentration of reactants at the surface also helps, but the basic cause of the increased rate is the lowered activation energy.

Answer: (4)

Out of syllabusAIPMT 2003

Keep practising — Surface Chemistry

2

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
3

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
4

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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