adsorption & colloids
Post on 07-Apr-2015
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Adsorption and Colloids Multiple choice Questions:1) The change in concentration in the interfacial layers between two phases of a system by surface forces is called a) Absorption a) Absorption b) Absorption c) Sorption d) Occlusion
2) The extent of adsorption of a gas on a solid depend on a) Nature of gas b) Pressure of gas c) Temperature of the system d) All the correct d) All the correct
3) Which of the following gases is adsored by charcoal? a) H2 b) N2 c) NH 3 d) CO2
Ans: (c) NH3 is easily liquifiable and highly water soluble gas.
4) Which is readily adsorbed by activated charcoal? a) Cl2 b) CO2 c) H2 d) SO2
Ans: (b) CO2 is preferably adsorbed by charcoal.
5) The process of adsorption must be a) Endoergic b) Endothermic c) Exothermic d) None
6) Charcoal adsorb not only gases but also acts as a) Reducing agent b) Oxidising agent c) Dehydrating agent d) All
7) Adsorption is accompanied by a) Increase in enthalpy of the system b) Decrease in enthalpy of the system b) Decrease in enthalpy of the system c) Decrease in temperature d) All the correct
Ans: (b) Enthalpy change of adsorption is negative as adsorption is exothermic process
8) Which of the following substances adsorb hydrogen gas most strongly? a) Silica gel b) Fe powder c) Platinum black c) Platinum black d) Activated carbon
9) The phenomenon in which adsorption and absorption takes place simultaneously is called a) Sorption b) Adsorption c) Desorption d) Deposition
10) The coloring matter which gets adsorbed on activated charcoal is called a) Adsorbate Adsorbate b) Adsorbent c) Adsorbent d) Adsorber
11) Colloids are good adsorbents due to a) their small surface area per unit mass. b) their large dimensions. c) their colligative properties. d) their large surface area per unit mass. d) their large surface area per unit mass.
12) The organic solvent that is used in chromatographic separation is termed as a) organosol b) solvent c) elutent c) elutent d) wash solution
13) The equilibrium attained in case of physical adsorption is a) static b) dynamic c) slow d) all these
14) The process of removal of an adsorbed substance from the surface of a solid is known as a) adsorption b) sorption c) desorption d) all of these
15) The substance which act as adsorbent are a) metals b) colloids c) silica gel d) all these
16) Increase in concentration of adsorbate at the surface of a substance as compaired to bulk is called a) negative adsorption b) positive adsorption b) positive adsorption c) desorption d) sorption
17) The curve indicating the variation of adsorption with temperature at constant pressure is known as a) adsorption isotherm b) adsorption isobar b) adsorption isobar c) adsorption isotherm d) adsorption isobar
18) Heat evolved per mole during chemisorption is in the order of a) 10 to 100 KJ b) 40 to 400 KJ c) 10 to 40 KJ d) 1 to 10 KJ
19) The heat evolved during adsorption in known as a) heat of sorption b) heat of desorption c) heat of absorption d) none of these d) none of these
Ans: (d) In fact, heat of adsorption
20) Which of the following is correct is case of Vander Waals adsortions? a) high temperature and high pressure b) low temperature and high pressure b) Low temperature and high pressure c) high temperature and low pressure d) low temperature and low pressure
21) Which of the following adsorption takes place at high temperature? a) physical adsorption b) chemical adsorption b) chemical adsortpion c) Vander Waals adsorption d) none of these
22) Which of the following is true regarding chemisorption? a) It is highly specific in nature it b) it is reversible in nature c) it usually occurs at low temperature d) it involves Vander Waals forces
23) Which of the following forms mono molecular layer of adsorbate on the surface of adsorbent? a) chemisorption b) chemical adsorption c) valency adsorption d) all are correct
24) The extent of physisorption a) decrease with rise in temperature b) increases with rise in temperature c) in independent of temperature d) first increases and then decreases with rise in temperature
25) Which one of the following is a properly of physical adsorption? a) non specific nature a) non specific nature b) high specificity c) irreversibility d) none
26) One which is not applicable to chemisorption is a) It is favoured by high temperature b) Effect of pressure is given by Freundlich adsorption adsorption c) It involves formation of monomolecular layer of adsorbate d) There is formation of chemical bonds between adsorbent and adsorbate Ans: (b)
27) Chemical adsorption is a) exothermic b) irreversible c) favoured by high temperature d) all of these
28) Point out the correct statement a) Freundlich equation is valid over a limited range of pressure. b) The constants K and n vary with temp. c) Freundlich adsorption equation is purely empirical formula d) All of the above d) All of the above
29) Which of the following substance are used for drying of gases. a) silica gel b) alumina c) both a and b c) both a and b d) neither a nor b
30) Which of the following acts as best adsorbent? a) charcoal b) activated charcoal c) carbon black d) activated coconut charcoal
31) Water is demineralised by passing through a) cationic exchange resins b) anionic exchange resins c) both a and b d) none
32) Adsorption indicators were first introduced by a) Dewar b) K. Fajan c) Domain d) Tschugaeff
33) Some statements are given about adsorption as (i) It is a surface phenomenon (ii) It involves energy changes (iii) It is an endothermic process (iv) It depends upon temperature Among the above, the correct statements are a) only i and ii b) i, ii and iii c) ii, iii and iv d) i, ii, and iv ii and iv Ans : (d)
i) Physisorption is very rapid (ii) Chemsorption is reversible iii) In Chemisorption multi molecular layer of adsorbate is formed iv) In physisorption chemical identity of the adsorbate remains same among these the true statement (s) is / are a) only i and ii c) only I b) only ii and iii d) only i iand iv d) only and iv
35) Colloidal particles carry charge, can be shown by? a) Tyndall effect b) Cataphoresis c) Brownian Movement d) Dialysis
Ans: (b) In applied electric field, the colloidal particles move towards electrode of opposite charge
36) Milk is an example of? a) Emulsion b) Suspension c) True solution d) Gel
Ans: (a) Liquid, fat globules dispersed in water medium is milk
37) Light scattering takes place in? a) Electrolysis solutions b) Colloidal solution b) Colloidal solution c) Electrodialysis d) Electroplating
Ans: (b) Optical property, Tyndall effect
38) Which of the following electrolysis is least effective in causing coagulation of ferric hydroxide sol? a) KBr b) K2SO4 c) K2CrO4 d)K4[Fe(CN6)]
Ans: (a) Ferric hydroxide has positive colloidal particles so need negative ion of electrolyte for coagulation. Br- ion minimum valency.
39) Which of the following forms a colloidal solution in water? a) NaCl b) Glucose c) Starch c) Starch d) Barium nitrate
40) Which of the following is not a colloidal solution of gas in liquid? a) Froath c) Mist b) Foams with tiny bubbles d) Whipped cream
Ans: (c) Mist is liquid in gas system.
41) Dust storm is? a) Dispersion of solid in gas b) Dispersion of a gas in solid c) Dispersion of solid in sold d) Dispersion of a gas in liquid
42) Gelatin is mostly used in making ice cream in order to? a) Prevent making a colloid. b) To stabilise the colloid and prevent crystallisation. To stabilise the colloid and prevent crystallisation. c) To stabilise mixture d) To enrich the aroma
Ans: (b) Gelatin is a protective colloid.
43) Movement of colloidal particle under the influence of electric field is called? a) Electrophoresis b) Dialysis c) Ionisation d) Electrodialysis
44) A negatively charged suspension of clay in water will need for precipitation the minimum amount of? a) AlCl3 b) K2SO4 c) HCl d) NaOH
Ans: Al3+ ion maximum valency i.e. 3. Therefore it has maximum amount is sufficient for precipatation.
45) The stability of lyophillic colloids is due to? a) Charge on their particles b) Smaller size of their particles c) Large size of their particles d) A layer of medium of dispersion of their particles layer of medium of dispersion of their particles
Ans: (d) The particles of lyophillic colloids are surrounded by molecules of dispersion medium solvent i.e. they are solvated.
46) Colloidal solution in which the dispersed phase has little affinity for the dispersion medium is called? a) Emulsions b) Lyophillic colloids c) Lyophobic colloids d) Hydrophillic colloids
Ans: (c) Lyophobic means solvent heating.
47) For Coagulation of As2S3 Which is most effective a) Na3PO4 b) MgCl2 c) CaCl2 d) AlCl3
Ans: (d) As2S3 sol particles are negatively charged due to adsorption of S2- ion. The Al3+ ion is opposite has more valency.
48) An emulsifier is a substance which? a) Homogenises the emulsion b) Stabilizes the emulsion c) Acce