Surface Chemistry HOTs Class 12 Chemistry

HOTs for Class 12

Question. Observe the given figure:

Surface Chemistry HOTs Class 12 Chemistry

Sanjeev performed this experiment with different solutions listed here :
Sugar solution (I), salt solution (II), ink (III),milk (IV), glucose solution (V), muddy water (VI),slaked lime (VII).
Tyndall cone can not be seen in
(a) Only I, II and VII
(b) I, IV and VIII
(c) II, III and IV
(d) I, II and V

Answer

D

Question. Which of the following acts as the best coagulating agent for ferric hydroxide sol?
(a) Potassium ferrocyanide
(b) Potassium chloride
(c) Potassium oxalate
(d) Aluminium chloride

Answer

A

Question. What is the role of adsorption in froth floatation process used especially for concentration of sulphide ores?
(a) Shape selective catalysts.
(b) Adsorption of pine oil on sulphide ore particles.
(c) Adsorption of pine oil on impurities.
(d) Production of heat in the process of exothermic reaction. 

Answer

B

Question. Colloidal solutions when prepared, generally contain excessive amount of electrolytes and some other soluble impurities. These soluble electrolytes if present in larger amount can coagulate the sol. So it is necessary to reduce their concentration to minimum amount.
Method I is used for purification and it can be converted to method II also.

Surface Chemistry HOTs Class 12 Chemistry

Advantage of method II over method I is
(a) it uses less energy
(b) it is cost friendly
(c) it speeds up the purification
(d) none of these.

Answer

C

Question. Which of the following is less than zero during adsorption?
(a) DG
(b) DS
(c) DH
(d) All of these.

Answer

D

Question. Which of the following factors contribute towards higher stability of lyophilic colloid?
(a) Charge on their particles.
(b) Attractive forces between particles.
(c) Small size of their particles.
(d) High solvation due to a layer of dispersion medium.

Answer

D

Question. Which of the following is not a method for coagulation of lyophobic sols?
(a) By electrophoresis
(b) By mixing oppositely charged sols
(c) By adding electrolyte
(d) By adding a protective colloid

Answer

D

Question. In Bredig’s arc method an electric arc is struck between the metal electrodes under the surface of water containing some stabilizing agent. The process involves

Surface Chemistry HOTs Class 12 Chemistry

(a) mechanical dispersion
(b) condensation
(c) both dispersion and condensation
(d) ultrasonic dispersion.

Answer

C

Question. Which out of the following electrolyte solutions having the same concentration will be most effective in causing the coagulation of arsenic sulphide sol?
(a) KCl
(b) MgCl2
(c) AlCl3
(d) Na3PO4

Answer

C

Question. In these colloids, a large number of small atoms or smaller molecules of a substance aggregate to form colloidal particles having size in colloidal range. These colloids are known as
(a) multimolecular colloids
(b) macromolecular colloids
(c) associated colloids
(d) lyophilic colloids.

Answer

A

Question. Substances which behave as normal electrolytes in solution at low concentration and exhibit colloidal properties at higher concentration are called
(a) lyophilic colloids
(b) lyophobic colloids
(c) macromolecular colloids
(d) associated colloids.

Answer

D

Question. Which of the following is not characteristic of chemisorption?
(a) Adsorption is specific.
(b) Heat of adsorption is of the order of 200 kJ mol–1.
(c) Adsorption is irreversible.
(d) Adsorption may be multimolecular layers. 

Answer

D

Question. A graph is plotted between log (x/m) and log

Surface Chemistry HOTs Class 12 Chemistry

Which of the following statements about this graph is not correct?
(a) The figure shows Freundlich adsorption isotherm.
(b) The figure shows Langmuir adsorption isotherm.
(c) The adsorption varies directly with pressure.
(d) The factor 1/n can have values between 0 and 1. 

Answer

B

Question. At CMC (critical micelle concentration) the surface molecules
(a) dissociate
(b) associate
(c) become bigger in size due to adsorption
(d) become smaller in size due to decomposition.

Answer

B

Question. After reading adsorption thoroughly Shubh plotted these 4 curves :
The given graphs/data I, II, III and IV represent general trends observed for different physisorption and chemisorption processes under mild conditions of temperature and pressure. Which of the following choice(s) about I, II, III and IV is(are) correct?

Surface Chemistry HOTs Class 12 Chemistry

Next day he showed these plots to his friend and asked about the plots and explained.
(i) Plot I represents physisorption because physisorption decrease with increase in temperature.
(ii) Plot II represents chemisorption as it initially increases upto certain extent and then decreases regularly.
(iii) Plot III represents physiosorption because it decreases with increase in both P & T.
(iv) Plot IV represents chemisorption because activation energy for it is of the order 80 – 240 kJ/mol.
The incorrect observations or explanations are
(a) (i) & (iii)
(b) (ii) & (iii)
(c) (i) & (iv)
(d) (iii) & (iv)

Answer

D

Question. Tyndall effect is observed only when which of the following conditions are satisfied?
(i) The diameter of the dispersed particles is not much smaller than the wavelength of the light used.
(ii) The refractive indices of dispersed phase and dispersion medium differ greatly in magnitude.
(iii) The size of the particles is generally between 10–11 and 10–9 m in diameter.
(iv) The dispersed phase and dispersion phase can be seen separately in the system.
(a) (i) and (iii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (i) and (ii)

Answer

D

Question. When an excess of a very dilute aqueous solution of KI is added to a very dilute aqueous solution of silver nitrate, the colloidal particles of silver iodide are associated with which of the following Helmholtz double layer?

Surface Chemistry HOTs Class 12 Chemistry
Answer

D

Question. Which of the following will not form a colloidal system?
(a) Solid-gas
(b) Liquid-gas
(c) Gas-gas
(d) Gas-liquid

Answer

C

Question. In the given figure label the parts.

Surface Chemistry HOTs Class 12 Chemistry

(a) A – Hydrophilic tail, B – hydrophobic head
(b) A – Hydrophobic tail, B – hydrophobic head
(c) A – Hydrophobic tail, B – hydrophilic head
(d) A – Hydrophilic tail, B – hydrophilic head

Answer

C

Question. Lyophilic sols are also called reversible colloids because
(a) they can be reformed by mixing residue (dispersed phase) in dispersion medium even after drying
(b) they can be easily precipitated from the colloidal system
(c) once formed, the dispersion medium and dispersed phase cannot be separated
(d) special reversible reactions are used to prepare them.

Answer

A

Question. A plot between log x/m (almost adsorbed) and log P has been plotted and it is shown below:

Surface Chemistry HOTs Class 12 Chemistry

Value of n is
(a) 2
(b) 0.5
(c) 1
(d) 1.5 

Answer

B

Question. Colloids can be classified as

Surface Chemistry HOTs Class 12 Chemistry

Choose the correct statement.
(a) Examples of P are cheese and jellies.
(b) Examples of Q are pumice stone and foam rubber.
(c) Examples of R are froth, whipped cream and soap lather.
(d) P is aerosol, Q is gel and R is foam. 

Answer

C

Question. Why is ferric hydroxide colloid positively charged when prepared by adding ferric chloride to hot water?
(a) Due to precipitation of ferric hydroxide there is an excess of Fe3+ ions.
(b) Due to preferential adsorption of Fe3+ ions by the sol of Fe(OH)3.
(c) Due to absence of any negatively charged ion.
(d) Due to adsorption of OH and Cl ions, the remaining sol has only Fe3+ ions. 

Answer

B

Question. The combination of two layers of opposite charges around the colloidal particles is called Helmholtz electrical double layer. The potential difference between the fixed layer and the diffused layer of opposite charges is called
(a) electrode potential
(b) zeta potential
(c) adsorption potential
(d) diffused potential.

Answer

B

Question. Excess KI solution is added to silver nitrate solution to prepare a silver iodide sol. The maximum precipitating power for this sol is possessed by
(a) K2SO4
(b) CaCl2
(c) Na3PO4
(d) Al2(SO4)3

Answer

D

Question. Collodion is a colloidal sol of
(a) Cellulose nitrate in ethanol
(b) Cellulose nitrate in benzene
(c) Cellulose nitrate in water
(d) None of these

Answer

A

Question. Surface tension of a lyophilic sol is generally _____ than that of the medium
(a) Equal
(b) Less
(c) More
(d) Twice

Answer

B

Question. Colloidal solution of gold in water is called
(a) Aqua dag
(b) Argyrol
(c) Purple of cassius
(d) Oil dag

Answer

C

Question. For adsorption
(a) ΔH is (–) ve
(b) ΔS is (–)ve
(c) ΔG is (–) ve
(d) All of these

Answer

D

Question. Flocculation value is expressed in terms of
(a) Millimoles of electrolyte per litre of solution
(b) Moles of electrolyte per litre of solution
(c) Grams of electrolyte per litre of solution
(d) Millimoles of electrolyte per millilitre of solution

Answer

B

Question. Butter is a colloid containing
(a) Fat dispersed in water
(b) Fat dispersed in oil
(c) Water dispersed in fat
(d) Water dispersed in starch

Answer

C

Question. Bredig’s arc method used for the preparation of metallic sols involves
(a) Dispersion
(b) Condensation
(c) Dispersion as well as condensation
(d) Neither dispersion nor condensation

Answer

C

Question. Which of the following colloidal dispersions is a true hydrophobic colloid?
(a) Gelatin
(b) Sulphur
(c) Starch
(d) Gum

Answer

B

Question. Micelles are
(a) Surfactant molecules
(b) Non-polar molecules
(c) Polar molecules
(d) None of these

Answer

A

Question. Zeolites are good shape selective catalyst due to their
(a) Honey comb like structure
(b) Two dimensional structure
(c) Close packed structure
(d) Orthorhombic structure

Answer

A

Question. Which of the following compound can form micelles?
(a) R—COOH
(b) RCOOR’
(c) (RCO)2O
(d) RCOONa

Answer

D

Question. The correct expression for Freundlich adsorption isotherm is,
(a) m/x = KP 1/n
(b) x/m = KP 1/n
(c) x/m = K /P 1/n
(d) xm = KP1/n

Answer

B

Question. In colloidal sulphur, molecules are held together by
(a) Hydrogen bonding
(b) Strong attraction forces
(c) van der Waal’s forces
(d) Strong electrical forces

Answer

C

Question. Which one of the following electrolytes brings about the coagulation of a gold sol quickest and in least concentration?
(a) NaCl
(b) AlPO4
(c) MgSO4
(d) Na2SO4

Answer

B

Question. Methods used for the preparation of colloidal solutions are
(a) Peptisation
(b) Hydrolysis
(c) Double decomposition
(d) All of these

Answer

D

Question. The correct decreasing order of the volumes of gases H2, CH4, CO2 and NH3 adsorbed by 1 g of charcoal at 288 K are in the order 
(a) H2 > CH4 > CO2 > NH3
(b) CH4 > CO2 > NH3 > H2
(c) CO2 > NH3 > H2 > CH4
(d) NH3 > CO2 > CH4 > H2

Answer

D

Question. Which of the following is correct?
(a) Chemical adsorption decreases with increases of temperature
(b) Chemical adsorption increases with increase of temperature
(c) Chemical adsorption first increases and then decreases with increase of temperature
(d) Chemical adsorption first decreases and then increases with increase of temperature

Answer

C

Question. Lyophilic sols have ________ between disperse phase and dispersion medium
(a) Strong attractive interaction
(b) Little attraction interaction
(c) Repulsive interaction
(d) Hydrogen bonding

Answer

A

Question. The potential difference between fixed charged layer and the diffused Layer having opposite charge is called
(a) Zeta potential
(b) Beta potential
(c) Alpha potential
(d) Gamma potential

Answer

A