Surface Chemistry JEE Main previous year questions with solutions

5 solved JEE Main questions on Surface Chemistry, free to read — no sign-in needed. The full chapter has 122 questions; sign in to attempt the remaining 117 in the exam simulator.

1. Q1JEE Main 2023 (13 Apr, Shift 2)
   Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : The diameter of colloidal particles in solution should not be much smaller than wavelength of light to show Tyndall effect. Reason R : The light scatters in all directions when the size of particles is large enough. In the light of the above statements, choose the correct answer from the options given below :
   1. A.Both A and R are correct but R is NOT the correct explanation of A
   2. B.A is true but R is false
   3. C.A is false but R is true
   4. D.Both A and R are correct and R is the correct explanation of A
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   Answer: (D)

   Conditions for Tyndall effect: (i) Diameter of colloidal particles in solution is not much smaller than wavelength of the light used. (ii) The refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude. If size of particles is large enough than light scatters in all directions. So Both A and R are correct and R is the correct explanation of A.
2. Q2JEE Main 2023 (13 Apr, Shift 1)
   What happens when a lyophilic sol is added to a lyophobic sol?
   1. A.Film of lyophilic sol is formed over lyophobic sol
   2. B.Lyophilic sol is dispersed in lyophobic sol
   3. C.Film of lyophobic sol is formed over lyophilic sol
   4. D.Lyophobic sol is coagulated
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   Answer: (A)

   Film of lyophilic sol is formed over lyophobic sol as lyophilic sol acts as a protective colloid. Lyophobic solutions are unstable in nature. When a lyophilic sol is added to lyophobic sol, stability of lyophobic sol increases due to a protective film of lyophilic sol present over the lyophobic sol.
3. Q3JEE Main 2023 (12 Apr, Shift 1)
   Four gases, $A,B,C$ and $D$ have critical temperatures $5.3,33.2,126.0$ and $154.3K$ respectively For their adsorption on a fixed amount of charcoal, the correct order is :
   1. A.$C\gt D\gt B\gt A$
   2. B.$C\gt B\gt D\gt A$
   3. C.$D\gt C\gt B\gt A$
   4. D.$D\gt C\gt A\gt B$
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   Answer: (C)

   Critical temperature of a gas is the temperature at or above which vapor of the gas cannot be liquefied, no matter how much pressure is applied. The extent of adsorption is directly proportional to the critical temperature of the gas. Higher is the critical temperature of the gas, greater is the extent of adsorption. Order of ${T}_{c}D\gt C\gt B\gt A$ Order of adsorption $D\gt C\gt B\gt A$
4. Q4JEE Main 2023 (11 Apr, Shift 2)
   The number of correct statements about modern adsorption theory of heterogeneous catalysis from the following is ...... A. The catalyst is diffused over the surface of reactants. B. Reactants are adsorbed on the surface of the catalyst. C. Occurrence of chemical reaction on the catalyst's surface through formation of an intermediate. D. It is a combination of intermediate compound formation theory and the old adsorption theory. E. It explains the action of the catalyst as well as those of catalytic promoters and poisons.
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   Answer: 3

   Adsorption theory of Heterogeneous catalysis involves five steps- Diffusion of reactants to the surface of the catalyst. Adsorption of reactant molecules on the surface of the catalyst. (Occurrence of chemical reaction on the catalyst’s surface through formation of an intermediate. Desorption of reaction products from the catalyst surface Making the surface available again for more reaction to occur. Diffusion of reaction products away from the catalyst’s surface.So, we can deduce from Adsorption theory of catalysis that as the concentration of reactants at active centres increases due to adsorption and thus the rate of the reaction is also increased.
5. Q5JEE Main 2023 (10 Apr, Shift 2)
   Ferric chloride is applied to stop bleeding because
   1. A.Blood absorbs ${FeCl}_{3}$ and forms a complex.
   2. B.${Cl}^{-}$ions cause coagulation of blood.
   3. C.${Fe}^{3+}$ ions coagulate blood which is a negatively charged sol.
   4. D.${FeCl}_{3}$ reacts with the constituents of blood which is a positively charged sol.
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   Answer: (C)

   Ferric chloride is a hemostatic agent, which means that it can be used to stop bleeding by promoting the coagulation of blood. Blood is a colloidal solution of an albuminoid substance and can be coagulated to form clot by applying ${Fe}^{3+}$ ion on the open wound. Thus, bleeding caused by a razor during shaving can be treated by rubbing potash alum against the cut which helps in the coagulation of the blood by sealing the blood vessels.