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Surface Chemistry Test - 4

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Surface Chemistry Test - 4
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Weekly Quiz Competition
  • Question 1
    4 / -1

    The size of colloidal particles ranges between

    Solution

    The size of colloidal particles is 10-5 to 10-7 cm which is intermediate between true solution and suspension.

  • Question 2
    4 / -1

    Which of the following will not form a colloidal system?

    Solution

    Gas-gas is a true so|ution.

  • Question 3
    4 / -1

    Fog is an example of colloidal system of

    Solution

    Liquid (water droplets) are dispersed in gas (air) in fog.

  • Question 4
    4 / -1

    A colloidal system in which liquid is dispersed phase and solid is dispersion medium is classified as

    Solution

    Gel is a colloidal system in which liquid is dispersed in a solid.

  • Question 5
    4 / -1

    Which of the following examples is correctly matched?

    Solution

    In gel, liquid is dispersed in solid.

  • Question 6
    4 / -1

    Mark the incorrect combination out of the following examples of colloidal solutions.

    Solution

    Gel has liquid dispersed in solid.

  • Question 7
    4 / -1

    Lyophilic sols are also called reversible colloids because

    Solution

    If the dispersed phase is removed completely from the colloidal system, it can be formed again by mixing dispersion medium with it.

  • Question 8
    4 / -1

    Which of the following factors contribute towards higher stability of lyophilic colloid?

    Solution

    Lyophilic colloids are highly solvated hence more stable.

  • Question 9
    4 / -1

    A lyophobic colloid cannot be formed by

    Solution

    Lyophobic colloids cannot be prepared by simple mixing of dispersed phase and dispersion medium.

  • Question 10
    4 / -1

    Which of the following is not the correct difference between lyophobic and lyophillic sols?

    Solution

    Lyophobic sols are irreversible while lyophilic sols are reversible.

  • Question 11
    4 / -1

    Which of the following is not correctly matched?

    Solution

    Gold sol is a Lyophilic colloid.

  • Question 12
    4 / -1

    Substances which behave as normal electrolytes in solution at low concentration and exhibit colloidal properties at higher concentration are called

    Solution

    At higher concentration the aggregated particles called micelles are formed by electrolytes like soap which act as colloidal particles.

  • Question 13
    4 / -1

    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

    Solution

    In multimolecular colloids the smaller particles aggregate and are held together by van der Waal's forces. e.g., sols of gold atoms and sulphur molecules.

  • Question 14
    4 / -1

    The substances which behave as colloidal solutions at higher concentration are called

    Solution

    Substances whose molecules aggregate spontaneously in a given solvent to form particles of colloidal dimensions are called associated colloids or micells.

  • Question 15
    4 / -1

    The formation of micelles takes place only above

    Solution

    The formation of micelles takes place only above a particular temperature called Kraft  temperature (TK).

  • Question 16
    4 / -1

    The critical micelle concentration (CMC) is defined as

    Solution

    CMC is the concentration below which no micellization takes place.

  • Question 17
    4 / -1

    At CMC (critical micelle concentration) the surface molecules:

    Solution

    At CMC, the particles of an electrolyte aggregate and form associated colloids known as micelles.

  • Question 18
    4 / -1

    In the given figure label the parts.

    Solution


    The RCOO- ion formed in the water contains two parts, a long hydrocarbon chain R (non-polar or hydrophobic tail) and a polar group COO- (polar or hydrophilic head).

  • Question 19
    4 / -1

    Soap mixed with water below critical micelle concentration behaves as

    Solution

    In lower concentration i.e., below critical micelle concentration (CMC) soap behaves like normal electrolytic solution.

  • Question 20
    4 / -1

    White of an egg whipped with water acts as

    Solution

    White of an egg whipped with water acts as a macromolecular colloid.

  • Question 21
    4 / -1

    Colloidal solutions of metals like gold can be prepared when their salt solutions react with certain substances like SnCl2, formaldehyde, phenyl hydrazine, etc.
    2AuCl3 ​ + 3SnCl2 ​ → 3SnCl4​ + 2Ausol ​
    The above method is an example of

    Solution

    Salt solution of gold is being reduced to gold by using a reducing agent like SnCl2.

  • Question 22
    4 / -1

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

    Solution

    The method involves both dispersion and condensation. The intense heat of arc vapourises some of the metal which condenses under cold water.

  • Question 23
    4 / -1

    When a small quantity of FeCl3 solution is added to the fresh precipitate of Fe(OH)3, a colloidal sol is obtained. The process through which this sol is formed is known as

    Solution

    Peptization involves conversion of freshly prepared precipitate into colloidal particles using a suitable electrolyte.

  • Question 24
    4 / -1

    Which of the processes is being shown in the figure?

    Solution

    When an electric field is applied to purify an impure colloidal solution, the process is known as electrodialysis. The ions present in the colloidal solution migrate out to the oppositely charged electrodes.

  • Question 25
    4 / -1

    Which of the following is not a method of removing impurities from a colloidal sol?

    Solution

    Distillation cannot be used to remove impurities from colloidal sol.

  • Question 26
    4 / -1

    Tyndall effect is observed only when
    (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 medium can be seen separately in the system.

    Solution

    Tyndall effect is observed only when these two conditions are satisfied.

  • Question 27
    4 / -1

    When a colloidal solution is viewed from the direction at right angles of light beam, the path of the beam is illuminated due to scattering of light In the figure (A) and (B) are

    Solution

    The bright cone of the light is known as Tyndall cone. The scattering of light is seen by the microscope.

  • Question 28
    4 / -1

    Tyndall effect is not observed in

    Solution

    Tyndall effect is due to the scattering of light by colloidal particles. Sugar solution is a true homogeneous solution which will not show Tyndall effect.

  • Question 29
    4 / -1

    Which of the following systems will show Tyndall effect?

    Solution

    Aqueous solution of Al(OH)3 will show Tyndall effect since it is a colloidal solution. All other solutions are true solutions.

  • Question 30
    4 / -1

    The cause of Brownian movement which is not shown by true solutions or suspensions is due to 

    Solution

    The colloidal particles are in a continuous zig-zag motion due to unbalanced bombardment of the particles by mole cules of the dispersion medium.

  • Question 31
    4 / -1

    Why is ferric hydroxide colloid positively charged when prepared by adding ferric chloride to hot water?

    Solution

    The adsorption of positively charged Fe3+ ions by the sol of hydrated ferric oxide results in positively charged colloid.

  • Question 32
    4 / -1

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

    Solution

    As excess of KI has been added, I- ions are adsorbed on Agl forming a fixed layer (and giving it a negative charge). It then attracts the counter ions (K+) from the medium forming a second layer (diffused layer).

  • Question 33
    4 / -1

    The combination of two layers of opposite charges around the colloidal particle is called Helmholtz electrical double layer. The potential difference between the fixed layer and the diffused layer of opposite charge is called 

    Solution

    The first layer of ions is firmly held and is termed as fixed layer while the second layer is mobile or diffused layer according to Helmholtz electrical double layer. The potential difference between fixed and diffused layer is called electrokinetic potential or zeta potential.

  • Question 34
    4 / -1

    Which of the following is not an explanation for the origin of charge on the colloidal particles?

    Solution

    Due to the presence of charge on colloidal particles, electrophoresis takes place.

  • Question 35
    4 / -1

    Movement of dispersion medium under the influence of electric field is known as

    Solution

    When movement of particles (electrophoresis) is prevented by some suitable means, it is observed that the dispersion medium begins to move in an electric field. This phenomenon is termed as electroosmosis.

  • Question 36
    4 / -1

    Why is alum added to water containing suspended impurities?

    Solution

    The water obtained from natural sources often contains suspended impurities. Alum is added to such water to coagulate the suspended impurities and make water fit for drinking purposes.

  • Question 37
    4 / -1

    Mixing of positively charged colloidal solution with negatively charged colloidal solution brings _____. The decreasing order of coagulating power of Na+, Ba2+ and AI3+ for negatively charged colloidal solution is _____.

    Solution

    According to Hardy Schulze rule, the coagulating power of an ion depends upon its valency. Higher the valency of ion, greater is its coagulating power.

  • Question 38
    4 / -1

    Which of the following acts as the best coagulating agent for ferric hydroxide sol?

    Solution

    The efficiency of coagulation of an electrolyte depends upon its valency. Thus [Fe(CN)6]4- is the best coagulating agent for Fe(OH)3 sol.

  • Question 39
    4 / -1

    Fe(OH)3 sol can be more easily coagulated by Na3PO4 in comparison to KCl because 

    Solution

    Ferric hydroxide is a positively charged sol hence ions carrying negative charge can coagulate it Since PO3-4 has higher negative charge than Cl- hence it is more effective for coagulation.

  • Question 40
    4 / -1

    Which out of the following electrolyte solutions having the same concentration will be most effective in causing the coagulation of arsenic sulphide sol?

    Solution

    As2S3 is a negatively charged soL To cause its coagulation, the ions must be positively charged. Greater the magnitude of positive charge, greater will be its coagulating power. Thus AlC13 containing Al3+ ion will be most effective in causing coagulation of As2S3.

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