Every Book Back multiple-choice question from Surface Chemistry (12th Standard Chemistry, Samacheer Kalvi) — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
Which of the following is incorrect for physisorption?
- A. reversible
- B. increases with increase in temperatureCorrect
- C. low heat of adsorption
- D. increases with increase in surface area
Explanation. Physisorption is an exothermic process involving weak van der Waals forces. According to thermodynamic principles, increasing the temperature provides energy that overcomes these weak attractions, leading to a decrease in the amount of gas adsorbed.
Q2
Which one of the following characteristics are associated with adsorption?
- A. \(\Delta G\) and \(\Delta H\) are negative but \(\Delta S\) is positive
- B. \(\Delta G\) and \(\Delta S\) are negative but \(\Delta H\) is positive
- C. \(\Delta G\) is negative but \(\Delta H\) and \(\Delta S\) are positive
- D. \(\Delta G\), \(\Delta H\) and \(\Delta S\) all are negative.Correct
Explanation. Adsorption occurs spontaneously, requiring a negative Gibbs free energy change. As particles are fixed to a surface, randomness decreases, making entropy change negative. The resulting release of energy makes the enthalpy change negative as well.
Q3
Fog is colloidal solution of
- A. solid in gas
- B. gas in gas
- C. liquid in gasCorrect
- D. gas in liquid
Explanation. Fog is an aerosol where the dispersed phase consists of fine liquid water droplets and the dispersion medium is the surrounding air, which is a gas.
Q4
Assertion : Coagulation power of \(Al^{3+}\) is more than \(Na^+\).
Reason : greater the valency of the flocculating ion added, greater is its power to cause precipitation
- A. if both assertion and reason are true and reason is the correct explanation of assertion.Correct
- B. if both assertion and reason are true but reason is not the correct explanation of assertion.
- C. assertion is true but reason is false
- D. both assertion and reason are false.
Explanation. The Hardy-Schulze rule states that the ability of an electrolyte to coagulate a colloidal solution depends on the charge of its ions. Higher valency ions are significantly more effective at neutralizing the charge on colloidal particles.
Q5
Statement : To stop bleeding from an injury, ferric chloride can be applied. Which comment about the statement is justified?
- A. It is not true, ferric chloride is a poison.
- B. It is true, \(Fe^{3+}\) ions coagulate blood which is a negatively charged solCorrect
- C. It is not true; ferric chloride is ionic and gets into the blood stream.
- D. It is true, coagulation takes place because of formation of negatively charged sol with \(Cl^-\).
Explanation. Blood is a negatively charged colloidal system. Ferric chloride acts as an electrolyte providing positive trivalent iron ions that neutralize the charge on the blood particles, leading to rapid coagulation and clotting.
Q6
Hair cream is
- A. gel
- B. emulsionCorrect
- C. solid sol
- D. sol
Explanation. Colloidal systems are classified by the state of their components. Hair cream consists of a liquid dispersed within another liquid medium, making it a classic example of an emulsion.
Q7
Which one of the following is correctly matched?
- A. Emulsion – Smoke
- B. Gel – butterCorrect
- C. foam – Mist
- D. whipped cream – sol
Explanation. In a gel, a liquid is dispersed throughout a solid medium. Butter fits this description perfectly. Other pairs are mismatched, such as smoke and mist being aerosols, while whipped cream is a foam.
Q8
The most effective electrolyte for the coagulation of \(As_2S_3\) Sol is
- A. \(NaCl\)
- B. \(Ba(NO_3)_2\)
- C. \(K_3[Fe(CN)_6]\)
- D. \(Al_2(SO_4)_3\)Correct
Explanation. Arsenious sulfide forms a negatively charged sol. To coagulate it, positive ions are needed. Aluminum ions carry a \(+3\) charge, making them more effective than monovalent or divalent cations in neutralizing the negative particles.
Q9
Which one of the is not a surfactant?
- A. \(CH_3 (CH_2)_{15} N (CH_3)_2 CH_2Br\)
- B. \(CH_3 (CH_2)_{15} NH_2\)Correct
- C. \(CH_3 (CH_2)_{14} CH_2 COONa\)
- D. \(CH_3 (CH_2)_{15} SO_2 Na\)
Explanation. Surfactants require a long hydrophobic chain and a highly polar or ionic head group to reduce surface tension effectively. A simple primary amine like hexadecylamine lacks the strong ionic character typical of industrial surfactants.
Q10
The phenomenon observed when a beam of light is passed through a colloidal solution is
- A. Cataphoresis
- B. Electrophoresis
- C. Coagulation
- D. Tyndall effectCorrect
Explanation. Tyndall effect is the scattering of light by colloidal particles, making the path of the beam visible in the solution.
Q11
In an electrical field, the particles of a colloidal system move towards cathode. The coagulation of the same sol is studied using \(K_{2}SO_{4}\) (i), \(Na_{3}PO_{4}\) (ii), \(K_{4}[Fe(CN)_{6}]\) (iii) and \(NaCl\) (iv). Their coagulating power should be
- A. II > I > IV > III
- B. III > II > I > IVCorrect
- C. I > II > III > IV
- D. none of these
Explanation. Since particles move to the cathode, the sol is positive. According to Hardy-Schulze rule, the coagulating power increases with the valency of the precipitating anion.
Q12
Collodion is a 4% solution of which one of the following compounds in alcohol – ether mixture?
- A. Nitroglycerine
- B. Cellulose acetate
- C. Glycoldinitrate
- D. NitrocelluloseCorrect
Explanation. Collodion is a flammable, syrupy solution of nitrocellulose in ether and alcohol.
Q13
Which one of the following is an example for homogeneous catalysis?
- A. manufacture of ammonia by Haber’s process
- B. manufacture of sulphuric acid by contact process
- C. hydrogenation of oil
- D. Hydrolysis of sucrose in presence of dil HClCorrect
Explanation. In homogeneous catalysis, the reactants and catalyst are in the same phase. Here, both sucrose and hydrochloric acid are in the liquid phase.
Q14
Match the following
A) \(V_{2}O_{5}\) i) High density polyethylene
B) Ziegler – Natta ii) PAN
C) Peroxide iii) \(NH_{3}\)
D) Finely divided Fe iv) \(H_{2}SO_{4}\)
- A. (iv) (i) (ii) (iii)Correct
- B. (i) (ii) (iv) (iii)
- C. (ii) (iii) (iv) (i)
- D. (iii) (iv) (ii) (i)
Explanation. Catalysts are matched to their industrial processes: vanadium pentoxide for sulfuric acid, Ziegler-Natta for polyethylene, peroxide for PAN, and iron for ammonia.
Q15
The coagulation values in millimoles per litre of the electrolytes used for the coagulation of \(As_{2}S_{3}\) are given below:
(I) (NaCl) = 52
(II) (\(BaCl_{2}\)) = 0.692
(III) (\(MgSO_{4}\)) = 0.224
The correct order of their coagulating power is
- A. III > II > ICorrect
- B. I > II > III
- C. I > III > II
- D. II > III > I
Explanation. Coagulating power is inversely proportional to the coagulation value. Electrolytes with lower coagulation values have higher coagulating power.
Q16
Adsorption of a gas on solid metal surface is spontaneous and exothermic, then
- A. \(\Delta H\) increases
- B. \(\Delta S\) increases
- C. \(\Delta G\) increases
- D. \(\Delta S\) decreasesCorrect
Explanation. Adsorption reduces the randomness of gas molecules as they settle on a surface, leading to a decrease in entropy (\(\Delta S\)).
Q17
If x is the amount of adsorbate and m is the amount of adsorbent, which of the following relations is not related to adsorption process?
- A. x/m = f(P) at constant T
- B. x/m = f(T) at constant P
- C. P = f(T) at constant x/m
- D. x/m = PTCorrect
Explanation. Standard adsorption variables describe relations between pressure, temperature, and amount adsorbed. The product relation \(x/m = PT\) is not a valid scientific adsorption relation.
Q18
On which of the following properties does the coagulating power of an ion depend?
- A. Both magnitude and sign of the charge on the ion.Correct
- B. Size of the ion alone
- C. the magnitude of the charge on the ion alone
- D. the sign of charge on the ion alone.
Explanation. According to the Hardy-Schulze rule, coagulation depends on both the valency (magnitude) and the nature of the charge (sign) of the ion relative to the sol.
Q19
Match the following
A) Pure nitrogen i) Chlorine
B) Haber process ii) Sulphuric acid
C) Contact process iii) Ammonia
D) Deacons Process iv) sodium azide (or) Barium azide
- A. (i) (ii) (iii) (iv)
- B. (ii) (iv) (i) (iii)
- C. (iii) (iv) (ii) (i)
- D. (iv) (iii) (ii) (i)Correct
Explanation. Processes are matched to their products: thermal decomposition of azides yields pure nitrogen, Haber yields ammonia, Contact yields sulfuric acid, and Deacon yields chlorine.
