adsorption & colloids

Download Adsorption & Colloids

Post on 07-Apr-2015

689 views

Category:

Documents

3 download

Embed Size (px)

DESCRIPTION

Multipal question and answers in power ppoint

TRANSCRIPT

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

Ans: (a)

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

Ans: (d)

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

Ans: (c)

6) Charcoal adsorb not only gases but also acts as a) Reducing agent b) Oxidising agent c) Dehydrating agent d) All

Ans: (a)

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

Ans: (c)

9) The phenomenon in which adsorption and absorption takes place simultaneously is called a) Sorption b) Adsorption c) Desorption d) Deposition

Ans: (a)

10) The coloring matter which gets adsorbed on activated charcoal is called a) Adsorbate Adsorbate b) Adsorbent c) Adsorbent d) Adsorber

Ans: (a)

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.

Ans: (d)

12) The organic solvent that is used in chromatographic separation is termed as a) organosol b) solvent c) elutent c) elutent d) wash solution

Ans: (c)

13) The equilibrium attained in case of physical adsorption is a) static b) dynamic c) slow d) all these

Ans: (b)

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

Ans: (c)

15) The substance which act as adsorbent are a) metals b) colloids c) silica gel d) all these

Ans: (d)

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

Ans: (b)

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

Ans:

(b)

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

Ans:

(b)

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

Ans:

(b)

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

Ans: (b)

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

Ans :

(a)

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

Ans:

(d)

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

Ans:

(a)

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

Ans:

(a)

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

Ans: (d)

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

Ans: (d)

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

Ans: (c)

30) Which of the following acts as best adsorbent? a) charcoal b) activated charcoal c) carbon black d) activated coconut charcoal

Ans:

(c)

31) Water is demineralised by passing through a) cationic exchange resins b) anionic exchange resins c) both a and b d) none

Ans:

(c)

32) Adsorption indicators were first introduced by a) Dewar b) K. Fajan c) Domain d) Tschugaeff

Ans:

(b)

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)

34)

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

Ans: (d)

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

Ans:

(c)

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

Ans: (a)

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

Ans: (a)

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