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Einstein Classes, Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road

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SURFACE CHEMISTRY

Sy l labus :

Adsorption - Physisorption and chemisorption andtheir characteristics, factors affecting adsorption ofgases on solids - Freundlich and Langmuiradsorption isotherms, adsorption from solution.

Catalysis - Homogeneous and heterogeneous,activity and selectivity of solid catalyst, enzymecatalysis and its mechanism.

Colloidal state - Distinction among true solutions,colloids and suspensions, classification ofcolloids - lyophilic, lyophobic; multi molecular,macromolecular and associated colloids (micelles),preparation of colloids - Tyndall effect, Brownianmovement, electrophoresis, dialysis, coagulationand flocculation; Emulsions and theircharacteristics;


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SURFACE CHEMISTRY

C1 Colloids : A colloid is a heterogeneous system in which one substance is disprersed (dispersed phase) as

very fine particles in another substance called dispersion medium. In a colloid, the dispersed phase mayconsist of particles of a single macromolecule (such as protein or synthetic polymer) or an aggregate ofmany atoms, ions or molecules. Colloidal particles are larger than simple molecules but small enough toremain suspended.

Difference between a solution and colloid is one of particle size.

True Solution : Colloid :

1. Homogeneous mixture & are transparent Heterogeneous mixture are transluscent

2. In as solution, the particles are ions or small Particles are visible under powerfulmolecules and invisible under all circumstances microscope but scattering effect by the particles

can be observed under ultra microscope

3. Particle size is of the order of molecule size Size of particle range of diameter between 1 andi.e. 1mµ or 10Å or < 103 pm or < µmm 1000 nm.

4. True solution passes easily through filter paper Colloidal particles passes easily through filteras well as animal memberane or parchment paper but slowly through parchment membranemembrane

5. Does not scatter light Particle scatter light i.e. Tyndall effect

6. Particle do not settle on ultracentrifugation Particle settle on ultracentrifugation

C2 Classification of colloids

Colloids are classified on the basis of the following criteria :

(a) Physical state of dispersed phase and disperseion medium

(b) Nature of interaction between dispersed phase and dispersion medium

(c) Type of particles of the dispersed phase

(a) Classification based on physical state of dispersed phase and dispersion medium

Eight types of colloidal syster are possible :

(solute) (solvent) Type of colloid ExamplesDispersed DispersedPhase Medium

1. Solid Solid Solid Sol Coloured glasses, Gemstone, Somealloys, minerals, rock salts.

2. Solid Liquid Sol Paints, cell fluids, starch or protein inwater, glue, gold sol, Indian ink, muddywater, milk of magnesia, white of an egg

3. Solid Gas Solid Aerosol Smoke, dust, storm, fumes

4. Liquid Solid Gel (solid emulsion) Cheese, butter, jellies, boot polish, curd,Fe(OH)

3, Al(OH)

3.

5. Liquid Liquid Emulsion Milk, hair cream, emulsified oils, codliver oil, medicines.

6. Liquid Gas Liquid Aerosol Fog, mist, cloud, insecticide spray.

7. Gas Solid Solid Foam Styrene foam, rubber, occluded gases,pumice stone, bread

8. Gas Liquid Foam or froth Whipped cream, soap, lather, lemonadefroth, beer, shaving cream, beaten egg


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If dispersion medium is water, the solution is called aquasol or hydrosal and if the dispersion medium isalcohol, it is called alcosol and so on.

(b) Classification based on nature of interaction between dispersed phase and dispersion medium. Theyare :

Lyophilic Colloid Lyophobic Collidal Solution

1. Solvent attracting (If water is the dispersion Solvent repelling (same here) i.e. ifmedium term used in hydrophilic water is the dispersion medium the

term used is hydrophobic

2. The word lyophilic means liquid loving The word lyophobic means liquidhating

3. Collidal sols directly formed by substances Subtances like metals, their sulphideslike gum, gelatine, starch, rubber etc. on etc. when mixed simply with dispersionmixing or warming with suitable liquid medium do not form colloidal sol. They(dispersion medium). can be prepared by special method.

4. If dispersion medium is seperated from These sols are readily precipitated ordispersed phase by evaporation, the sol coagulated on the addition on thecan be reconstituted by simply remixing addition of small amount of electrolyteswith the dispersion medium by heating or by shaking and hence are

not stable

5. Thus these sols are reversible sols Once they precipitate they do not giveback the collidal sol by simple additionof the dispersion medium. These solsare Irreversible.

Viscosity is much higher than dispersion medium whereas Lyophobic sol have of same as of dispersionmedium. Lyophobic sols need stablising agent for their preservation.

(c) Classification based on type of particles of the Dispersed Phase : They are

1. Multimolecular colloid

2. Macromolecular colloid

3. Associated colloid

1. Multimolecular Colloid : When on dissolution, a large number of atoms or smaller molecules of asubstance aggragate together to form species having size (with diameter less than 1 nm) e.g. Gold sol maycontain particles of various sizes having many atoms. Sulphur sol consists of particles containing athousand or more of S

8 sulphur molecules.

2. Macromolecular Colloid : Macro molecules have large molecular masses. These on dissolution in asuitable solvent form a solution in which the size of the macromolecules may be in the collidal range. Suchsystems are called macro-molecular colloid. These colloids are quite stable and resemble true solution inmany respect. e.g. naturally occuring macromolecules are strach, collulose, proteins, and enzymes.Examples of man-made macromolecules are polythene, nylon, polystyrene, synethetic rubber etc.

3. Associated Colloids (Micelles) : These are some substance which at low concentrations hehave as normal,strong electrolytes but at higher concentrations exhibit colloidal behaviour due to formation of aggregatedparticles. The aggregated particles thus formed are called micelles. These are known as associated colloid.The formation of micelles takes place only above a particular temperature called “Kraft Temperature” (T

k)

and above particular concentration called “Critical Micelle concentration (CMC)”. On dilution, thesecolloids revert back to individual ions. e.g. surface active agents soaps, detergents belong to this class. Forsoaps CMC is ~ 10–4 to 10–3 mol L–1. These colloid have both lyophilic and lyophobic part. Micelles maycontain as many as 100 molecules or more


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Mechanism of Formation of Micelle

e.g. let us take example of soap solution i.e. RCOO–Na+ (soap is sodium salt of high fatty acids e.g. sodiumstearate) i.e. CH

3(CH

2)

16COO–Na+ or sodium Lauryl Sulphate CH

3(CH

2)

11SO

4Na+

In

Polar part is water loving whereas non-polar part water repelling. Thus RCOO– present with COO– part inwater and R staying away from it and remain on surface. With higher concentration they are pulled in water.An aggregrate thus formed called ionic micelle.

C3 Prepration of collidal solution :

1. Preparation of Lyophobic solutions :

(a) Condensation method (b) Dispersion method

(a) Condensation Method :

1. Chemical Method

2. Physical Method

(i) Exchange of solvent

(ii) Excessive cooling

1. Chemical Method : Colloidal solutions can be prepared by chemical reactions leading to formation ofmolecules by double decomposition, oxidation, reduction and hydrolysis. These molecules then aggregateleading to formation of sols, provided a suitable stabliser is present.

(i) Oxidation : A colloidal solution of sulphur can be obtained by bubbling oxygen or any other oxidisingagent like HNO

3, Br

2 etc. through a solution of hydrogen sulphide in water

2H2S + O

2 2H

2O + 2S

(ii) By reduction : A number of metals, such as silver, gold and platinum have been obtained in colloidal stateby treating the aqueous solution of their salts with a suitable reducing agent, such as formaldehyde,hydrazine, H

2O

2, SnCl

2 etc.

2AuCl3 + 3SnCl

2 3SnCl

4 + 2Au

(iii) By hydrolysis : Many salt solutions are easily hydrolysed by boiling dilute solutions of their salts. e.g.Fe(OH)

3 and Al(OH)

3 sol are obtained by boiling solutions of corresponding chlorides.

FeCl3 + 3H

2O Fe(OH)

3 + 3HCl

(iv) By double decomposition : A solution of arsenic sulphide is obtained by passing H2S through a cold

solution of arsenious oxide in water.

As2O

3 + 3H

2S As

2S

3 + 3H

2O

(b) Dispersion Method : In these methods the coarser particles are broken to smaller particles of colloidal sizein the presence of dispersion medium. These are stabilized by adding suitable stabilizer.

(i) Mechanical Dispersion : In this method, the coarse suspension of the substance is brought into colloidalstate in the dispersion medium by grinding in a colloid mill.

(ii) Electrical dispersion or Bredig’s Arc method : This process involve dispersion as well ascondensation. If an electric arc is struck between two electrodes of a metal like gold, silver, platinum orcopper in water having traces of an alkali, the metal is found to be converted into colloidal solution. AlkaliAct as stabliser.


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(iii) Peptization : The process of converting precipitate into colloidal solution by shaking it with dispersionmedium in the presence of (small amount of) electrolyte. The electrolyte used for this purpose is calledpeptizing agent or stablizing agent. During peptization, the precipitate absorbs one of the ions of theelectrolyte on its surface.The ion absorbed on the surface is common either with the anion or cation of theelectrolyte. This causes the development of positive or negative charge on precipitates which ultimatelybreak-up into small particles having the dimensions of colloids. e.g. Freshly prepared Fe(OH)

3 can be

converted into colloidal state by shaking it with H2O containing FeCl

3 or NH

4OH

Fe(OH)3 + FeCl

3 [Fe(OH)

3Fe]3+ + 3Cl–

Stable solution of stannic oxide collodial is obtained by adding small amount of dilute HCl to stannic oxideprecipitate. Similarly colloidal solution Al(OH)

3 and AgCl are obtained by treating corresponding ppt. with

dilute HCl and AgNO3 or KCl respectively. Gelatin stablised colloidal state of ice-cream. Lamp black is

peptised by gums to form indian ink.

C4A Purification of Colloidal Solution :

1. Dialysis : Dialysis may be defined as the process of seperating a crystalloid from a colloid by diffusion orfiltration through a fine memberane, the memberane (or appratus) used for this purpose is called Dialyser.The process of dialysis can be quickened by using hot water or by applying electric feild (electrodialysis).

2. Ultra filtration : Solution particles pass directly through the ordinary filter paper because their pores arelarger (more than 1 µ or 1000 mµ) then the size of solution particles (less than 200 mµ). But if the pores ofordinary filter paper made smaller by soaking the filter paper in a solution of gelatin and subsequentlyhardened by soaking in formaldehyde, the filter paper may retain colloidal particles and allow true solutionparticle to escape. Such filter is known as ultrafilter paper.

3. Ultra-Centrifugation : In this method, the colloidal solution is taken in a tube which is place in aultra-centrifuge on rotation the colloid particle settle down at the bottom of the tube.

C4B Properties of Colloidal System :

(i) Heterogeneous character : As it contain two phases i.e. dispersed phase and dispersion medium.

(ii) Non-Setting : Colloidal solutions are stable systems.

(iii) Filterability : Colloidal particles readily pass through ordinary filter paper. However they can be retainedby special filters known as ultrafilters.

(iv) Visibility : not visible under most powerful microscope.

(v) Colour : Colour of a colloidal solution depends on the size and shape of particle.

(vi) Colligative Properties : Colloidal solutions shows colligative properties i.e. relative lowering in V.P.,somotic property, elevation in B.pt., Depression in fz. pt. However due to high molecular masses ofcolloidal particles, mole fraction of the dispersed phase is very low. Thus value of colligative propertiesdetermined experimentally are colligative properties determined experimentally is very low. Only osmoticpressure measument is used to determine the molecular mass of polymer.

(vii) Tyndall Effect (optical property) : Tyndall in 1869, observed that when a beam of light is passed througha true solution is can not be seen. When a same light is passed through a colloidal solution it become visibleas a bright streak. This phenomenon is called Tyndall effect and illuminated path (streak of light) is knownas Tyndall cone. The appearance of dust particles in a semidarkened room when a sun beam enters or whena light is thrown from a projector in cinema hall are well known example of Tyndall effect. The dustparticles are large enough to scatter light which renders the path of light visible.

(viii) Brownian Movement : Robert Brown, observed that pollen grain in aqueous suspension were in constantmotion. When colloidal solutions are observed in ultramicroscope, the particles are in constant, random orzig-zag motion, not following the definite path called as Brownian motion. Brownian movement is due tocollision of colloidal particles with dispersion medium which are in constant motion. Since colloidalparticles are heavier than dispension medium molecules their movement is considerably slower than that ofmedium molecules. The mass of particle of ordinary suspension is so large that the bombardment ofmolecules of the dispersion medium produces little effect and thus ordinary suspension do not exhibitbrownian movement.


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(ix) Electrical Property : Colloidal particles are electrically charged. All the particles of a colloidal systemcarry the same charge while the dispersion medium has an equal but opposite charge with the result thesystem as a whole is electrically natural. Colloidal particles having similar charge, repel each other, and donot combine to form bigger particles and thus solution is stable and particles do not settle down. When anelectric current is passed through a colloidal solution the solid particles and the liquid medium beingoppositely charged move in opposite direction. In case the experiment is so arranged that only the particlescan move and no liquid medium, the phenomenon is known as Cataphoresis or Electrophoresis.

When only the medium is allowed to migrate and not the particles, then is known as electrosmosis.

Distance travelled by colloidal particles in one second under a potential gradient of 1 volt per cm is calledelectrophoretic mobility of colloidal particles.

(x) Origin of the charge on colloidal particles :

The origin of the charge on the sol particles in most cases is due to the preferential of either positive ornegative ions on their surface. When two or more ions are present in the dispersion medium differentialadsorption of common to the colloidal particle usually takes place. e.g. Fe(OH)

3 sol prepared by the

hydrolysis of ferric chloride has positive charge because of the preferential adsorption of ferric ions i.e.Fe3+ on the surface of the ferric hydroxide particles.

Fe(OH)3 + Fe3+ Fe(OH)

3 . Fe3+

Some other positively charged colloidal sols are Al(OH)3, Heamoglobin, basic dyes etc. Similarly, the

negative charge on the arsenic sulphide sol is found to be due to preferential adsorption of sulphide ions,produced by the ionization of H

2S. Other negatively charged sol are starch acidic dyes etc.

C5 Co-agulation of colloidal solutions :

As stability of the colloidal state is due to existance of electrical charge on the particles. If charge is loweredto a certain critical value or neutralised, the particles approach close enough to coalesce to form biggerparticles of the suspension range.

This phenomenon of change of colloidal state to suspension state is known as coagulation or flocculationof colloidal solution. It is generally brought about by following treatments :

(i) By the mutual action of sols (mutual precipitation) : When the two oppositely charged sols e.g. As2S

3

and Fe(OH)3 sols are mixed in approximately equal proportions, the charge of one sol is neutralised by the

opposite charge on the other sol with the result the dispersed phase of both the sols are precipitated out.

(ii) By the addition of electrolytes : Although traces of an electrolyte are essential for stablising the sols,presence of large amounts causing their coagulation or flocculation.

As colloidal particles carry opposite charge ions, they take up oppositely charged ions from electrolyteswith the result the charge on the sol particles is neutralised and thus these are precipitated. The ion carryopposite charge is called Flocculating ion. e.g. The amount of electrolyte required to coagulate a fixedamount of a sol depends upon the valency of the flocculating ion. In general, greater the valency of theflocculating ion the higher is its power to cause precipitation. This is known as Hardy - Schulze rule.

Flocculation power of the various ions follows the following order :

Cations : Al3+ > Mg2+ > Na+

Anions : [Fe(CN)6]4– > PO

43– > SO

42– > Cl–

Flocculating cations and anions cause coagulation (floculation) of the negatively and positively chargedcolloids respectively. The minimum concentration required to cause flocculation is known asFlocculation value, which is generally expressed in milli mol per litre.

C6 Protective colloids : Lyophilic sol added to a lyophobic colloid prevent from precipitation by electrolyte,the lyophilic sol added to a lyophobic sol, provide envelop to the particles of lyophobic sol, and thus protectis from the action of electrolytes. This lyophilic colloids used for such purposes are known as protectivecolloids. e.g. addition of gelatin (lyophilic colloid) to a gold sol (lyophobic sol) protects the latter by theaction of limited amount of NaCl. The lyophilic colloids differ in their protective powers.


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Gold Number : is used to measure the protective power of different colloids. It is defined as weight inmilligrams of a protective colloid which checks the co-agulation of 10mL of a given gold solution of adding1 mL of a 10% solution of sodium chloride. Thus smaller the gold no. of a lyophilic colloid greater is theprotective power.

Q. 0.025 g of starch sol. is required to prevent coagulation of 10mL gol sol when 1 ml of 10% NaClsolution is present. What is the gold number.Solution :By def. amount of protective sol. in mg is required to prevent the coagulation of 10 mL gold sol when10% NaCl solution is added. Thus amount of starch required is 0.025 g i.e. 25 mg thus gold numberis 25.There is another term called “Rubin number” which is defined as the amount of protective colloid inmilligrams which prevents the colour change in 100 mL of 0.01% congo rubic dye to which 0.16 gmequivalent of KCl is added.

C7 Emulsions : Emulsions are those colloidal systems in which the dispersed phase is liquid normally.The two common examples are :Milk : Which consists of particles of liquid fat dispersed in water.Cod Liver Oil : in which particles of water are dispersed in oil.Particles of dispersed phase are generally bigger then those in sols and are sometime visible inmicroscope. Emulsions, particles carry a negative charge and are sensitive to addition of electrolytes. Theyshow Tyndall effect and Bownian movement. In most of emulsions the two liquid phases are oil and waterand thus emulsions may be of following two types.

1. Oil in water emulsion : In these emulsions, oil is the dispersed phase and water is dispersion medium milkand vanishing cream are two important examples.

2. Water in oil emulsion : Water is dispersed phase and oil is dispersion medium e.g. Butter and Cold Cream.FOAM : are colloidal dispersions of gas in liquid, which is stabilized by soap or other surface activeagents. Industrial application of foam : (i) in ore floatation (ii) in detergency (iii) in fire fighting etc.

C8A ADSORPTIONAdsorption is defined as phenomenon of attracting & retaining the molecules on the surface of a liquid ora solid resulting into a higher concentration of the molecules on the surface is called adsorption.Process of removal of adsorbed particle called as desorption. The susbtance which is adsorbed on surfaceis called adsorbate. The substance on which adsorption takes place is adsorbent e.g. charcoal, silica gel,alumina gel, clay etc. are very good adsorbentAbsorbtion : The molecule of substance are uniformly distributed througout the body of a solid or a liquid.In certain cases both absorption & adsorption takes place simultaneously called as sorption.Adsorption is of two types :

Physisorption ChemisorptionH adsorption is low 20 kJ/mol H adsorption is high ~ 200 kJ/molMolecule of adsorpate & adsorbent are Held by chemical bondsheld by weak vander wall forcesTake place at low temperature & decreases Take place at high temperaturewith TNot very specific Very specificMultimolecular layer formed Usually monomolecular layer is formed.

C8B


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1. Freundlich Adsorption Isotherm (at temp. T)x Amount of Adsorbatem Amount of AdsorbantkP1/n, n > 1, P Pressure of gas adsorbedk, n are parameter depend on nature of gas and solid.

n/1kPm

x Plog

n

1klog

m

xlog

value of k & n can be find out.

2. Langmuir Adsorption Isotherm : Applicable to chemisorption bP1

ap

m

x

a, b Langmuir ParameterBy reversing equation :

P

1.

a

1

a

b

aP

bP1

x

m

a, b can be calculatedbP1

ap

m

x

At. low pressure bp < < 1, thus aPm

x

At high pressure pb > > 1, thus b

a

bP

aP

m

x (constant)


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1. Which requires catalyst

(a) S + O2 SO

2

(b) 2SO2 + O

2 2SO

3

(c) C + O2 CO

2

(d) All

2. During hydrogenation of oils catalyst commonlyused is

(a) Pd or CuCl2

(b) Finely divided Ni

(c) Fe

(d) V2O

5

3. Which is used in the Haber’s process for themanufacture of NH

3

(a) Al2O

3(b) Fe + Mo

(c) CuO (d) Pt

4. Which is not correct for heterogeneous catalysis

(a) The catalyst decreases the energy ofactivation

(b) The surface of catalyst plays animportant role

(c) The catalyst actually forms a compoundwith reactants

(d) There is no change in the energy ofactivation

5. Catalytic poisoners act by

(a) Coagulating the catalyst

(b) Getting absorbed on the active centres onthe surface of catalyst

(c) Chemical combination with any one ofthe reactants

(d) None

6. Protons accelerate the hydrolysis of esters. This isan example of

(a) A heterogeneous catalysis

(b) An acid-base catalysis

(c) A promoter

(d) A negative catalyst

7. Mark the correct statement about given graph

E X E R C I S E (OBJECTIVE)

(a) X is threshold energy level

(b) Y and Z are energy of activation forforward and backward reactionrespectively

(c) Q is heat of reaction and reaction isexothermic

(d) All

8. The catalyst used in the contact process of sulphuricacid is

(a) Copper

(b) Iron

(c) Vanadium pentoxide or Pt (asbestos)

(d) Ni

9. Which explains the effect of a catalyst on the rateof a versible reaction

(a) It provides a new reaction pathway witha lower activation energy

(b) It moves the equilibrium position to theright

(c) It increases the kinetic energy of thereacting molecules

(d) It decreases the rate of the reversereaction

10. For absorption of gas on solid surface, the plots oflog x/m vs log P is linear with a slope equal to

(a) K

(b) log K

(c) l n K

(d) 1 / n (n being integer)

11. Which statement about enzymes is not correct

(a) Enzymes are in collodial state

(b) Enzymes are catalysts

(c) Enzymes can catalyse any reaction

(d) Urease is an enzyme

12. Which is not true in case of catalyst

(a) The catalyst is unchanged chemistry atthe end of a reaction

(b) The catalyst accelerates the reaction

(c) In a reversible reaction, the catalystalters the equilibrium position

(d) A small amount of catalyst is oftensufficient to bring about a large changein reaction


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13. Which type of metals form effective catalyst

(a) Alkali metals

(b) Transition metals

(c) Alkaline earth metals

(d) Radioactive metals

14. A catalyst increases the rate of reaction because it

(a) Increases the activation energy

(b) Decreases the energy barrier for reaction

(c) Decreases the collision diameter

(d) Increase the temperature coefficient

15. Which is wrong in case of enzyme catalysis

(a) Enzymes work best at an optimumtemperature

(b) Enzymes work at an optimum pH

(c) Enzymes are highly specific forsubstrates

(d) An enzyme raises activation energy

16. Air can oxidise sodium sulphite in aqueoussolution but cannot do so in the case of sodiumarsenite. If however, air is passed through asolution containing both sodium sulphite andsodium arsenite then both are oxidised. This is anexample of

(a) Positive catalysis

(b) Negative catalysis

(c) Induced catalysis

(d) Auto-catalysis

17. The oxidation of oxalic acid by acidified KMnO4

becomes fast as the reaction progresses due to

(a) Auto catalysis by Mn2+

(b) Presence of SO42—

(c) Presence of K+

(d) Presence of MnO4—

18. Which is universally correct for the catalyst

(a) Initiates reaction

(b) Does not initiate reactions

(c) Does not alter the nature of products

(d) Is not specific in nature

19. The catalyst iron, employed in the Haber’s process,contains molybdenum, the function of which is

(a) To increase the rate of combination ofgases

(b) To counterbalance for the presence ofimpurities in the gases

(c) To act as a catalyst promoter and increaseactivity of catalyst

(d) To make up for the adverse temperatureand pressure conditions

20. The minimum energy level necessary to permit areaction to occur is

(a) Internal energy

(b) Threshold energy

(c) Activation energy

(d) Free energy

21. According to Langmuir absorption isotherm theamount of gas absorbed at very high pressure

(a) Reaches a constant limiting value

(b) Goes on increasing with pressure

(c) Goes on decreasing with pressure

(d) Increases first and decreases later withpressure

22. Which of the following type of catalysis can be ex-plained by the absorption theory

(a) Homogenous catalysis

(b) Acid-Base catalysis

(c) Heterogeneous catalysis

(d) Enzyme catalysis

23. The reaction rate at a given temperature is slowerwhen

(a) The energy of activation is higher

(b) The energy of activation is lower

(c) Entropy changes

(d) Initial concentration of the reactantremains constant

24. Which is not correct for catalyst. If

(a) Enhances the rate of reaction in bothdirections

(b) Changes enthalpy of reaction

(c) Reduces activation energy of reaction

(d) Specific in nature

25. Which process does not involve a catalyst

(a) Haber’s process

(b) Thermite process

(c) Ostwald’s process

(d) Contact process

26. Which plot is the absorption isobar forchemisorption where X is the amount of gasabsorbed on mass m (at constant pressure) attemperature T.

(a)


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(b)

(c)

(d)

27. In the titration between oxalic acid and acidifiedpotassium permanganate, the manganous saltformed during the reaction catalyses the reaction.The manganous salt acts as

(a) A promoter

(b) A positive catalyst

(c) An auto-catalyst

(d) None of the above

28. Which equation represents Freundlisch absorbtionisotherm (physical adsorption is basis of this theory)

(a)n/1)P(K

m

x where x is amount of gas

absorbed on mass ‘m’ at pressure P

(b) Plogn

1Klog

m

xlog

(c) KPm

x at low pressure and K

m

x

at high pressure

(d) All

29. The function of negative catalyst is

(a) To remove the active intermediate fromthe reaction

(b) To terminate the chain reaction

(c) Both (a) and (b)

(d) None

30. Zeolites

(a) Are microporous aluminosilicates

(b) Have general formula Mx/n [(AlO2)x

(SiO2)

4].mH

2O

(c) Have pore sizes between 260 pm to740 pm

(d) All

31. The phenomenon in which absorption andabsorption takes place simultaneously is called

(a) Desorption (b) Sorption

(c) Both (a) and (b) (d) None

32. The extend of absorption of a gas on a soliddepends on

(a) A nature of gas

(b) Pressure of gas

(c) Temperature of the system

(d) All

33. An increase in the concentration of absorbate atthe surface relative to its concentration in bulkphase is called

(a) Adsorption (b) Enthalpy

(c) Absorption (d) None

34. On adding few drops of dil. HCl or FeCl3 to freshly

precipitated ferric hydroxide, a red colouredcollodial solution is obtained. This phenomenon isknown as

(a) Preptization (b) Dialysis

(c) Protection (d) Dissolution

35. Which is not shown by sols

(a) Adsorption (b) Tyndall effect

(c) Flocculation

(d) Paramagnetism

36. The arsenious sulphide sol has negative charge. Themaximum coagulating power for precipitating it isof

(a) 0.1 N Zn (NO3)

2(b) 0.1 N Na

3PO

4

(c) 0.1 N ZnSO4

(d) 0.1 N AlCl3

37. Lyophilic sols are more stable than lyophobic solsbecause

(a) The collodial particles have positivecharge

(b) The collodial particles have no charge

(c) The collodial particles are solvated

(d) There are strong electrostatic repulsionsbetween the negatively charged collodialparticles.


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38. Which forms a collodial solution in water

(a) NaCl (b) Glucose

(c) Starch (d) Barium nitrate

39. Collodial solution of arsenious sulphide can beprepared by

(a) Electrodispersion method

(b) Peptization

(c) Double decomposition

(d) Hydrolysis

40. Gold number gives

(a) The amount of gold present in thecolloid

(b) The amount of gold required to break thecolloid

(c) The amount of gold required to protectthe colloid


41. Collodial solutions are not purified by

(a) Dialysis (b) Electrodialysis

(c) Electrophoresis (d) Ultrafiltration

42. Gold number :

(a) May be defined as the milligram of thedry material of which the hydrophilic solis prepared and which when added to10 mL of red gold sol, will prevent it fromcoagulation on the addition of 1 mL of10 per cent sodium chloride solution

(b) May be defined as the milligram of thedry material of which the hydrophilic solis prepared and which when added to1 mL of red gold sol, will prevent it fromcoagulation on the addition of 10 mL of10 per cent sodium chloride solution

(c) May be defined as the milligram of thedry material of which the hydrophilic solis prepared and which when added to1 mL of red gold sol, will prevent it fromcoagulation on the addition of 1 mL of1 per cent sodium chloride solution


43. The movement of sol particles under an appliedelectric field is called

(a) Electro deposition

(b) Electrodialysis

(c) Electro-osmosis

(d) Electrophoresis

44. The average size of the colloids is of the order

(a) 10–4 cm to 10–2 cm

(b) 10–5 cm to 10–7 cm

(c) 10–7 cm to 10–10 cm

(d) 10–1 cm to 10–2 cm

45. The separation of collodial particles(or purification of sol) from particles of moleculardimensions is known as

(a) Photolysis (b) Dialysis

(c) Pyrolysis (d) Peptization

46. Gelatin is often used as an ingredient in themanufacture of ice-cream. The reason for this is

(a) To prevent the formation of a colloid

(b) To stabilize the colloid and preventcrystal growth

(c) To cause the mixture of solidify

(d) To improve the flavour

47. Preptization is a process of

(a) Precipitating colloidal particles

(b) Purifying colloidal particles

(c) Dispersing the precipitate into colloidalstate

(d) None

48. A liquid aerosol is a colloidal system of

(a) A liquid dispersed in a solid

(b) A liquid dispersed in a gas

(c) A gas dispersed in a liquid

(d) A solid dispersed in a gas

49. Gold number of a lyophilic sol refers that

(a) Larger is its value, the greater is thepeptizing power

(b) Lower is its value, the greater is thepeptizing power

(c) Lower is its value, the greater is theprotecting power

(d) Larger is its value, the greater is theprotecting power

50. Gold number is minimum in case of

(a) Gelatin (b) Egg albumin

(c) Gum arabic (d) Starch

51. When dilute aqueous solution of AgNO3 (excess) is

added to KI solution, positively charged solparticles of AgI are formed due to absorption ofion

(a) K+ (b) Ag+

(c) I— (d) NO3

—

52. The charge on As2S

3 sol is due to the absorption of

(a) H+ (b) OH—

(c) O2

— (d) S2—


New Delhi – 110 018, Ph. : 9312629035, 8527112111

CSC – 13

53. The Rubin number which was proposed by Ostwaldas an alternative to the Gold number in order tomeasure the protective efficiency of a lyophiliccolloid may be defined as the

(a) Mass is milligram of a colloid per 100 mLof solution which just prevents thecolour change of standard sol of dyeCongo-Rubin from red to violet when0.16 g eq. KCl is added to it

(b) Mass in gram of a colloid per 100 mL ofsolution which just prevents the colourchange of standard sol of dyeCongo-Rubin from red to violet when0.1 M KCl is added to it

(c) Mass in gram of a colloid per 100 mL ofsolution which just prevents the colourchanged of standard sol of dyeCongo-Rubin from red to violet when0.2 M KCl is added to it

(d) Mass in gram of a colloid per 100 mL ofsolution which just prevents the colourchange of standard sol of dyeCongo-Rubin from red to violet when1 M KCl is added to it

54. If dispersion medium is water, the colloidal systemis called

(a) Sol (b) Aerosol

(c) Organosol (d) Aquasol

55. Lyophobic colloids are

(a) Reversible colloids

(b) Irreversible colloids

(c) Protencitve colloids

(d) Gum, proteins

56. Which is not related with colloids

(a) Brownian movement

(b) Dialysis

(c) Ultrafiltration

(d) Wavelength

57. Flocculation value is expressed in terms of

(a) Millimole per litre

(b) Mol per litre

(c) Gram per litre

(d) Mol per millilitre

58. Which one is a colloid

(a) Urea (b) Cane sugar

(c) Sodium chloride(d) Blood

59. The property of colloidal suspension used todetermine the nature of charge on the particles is

(a) Dialysis

(b) Electrophoresis

(c) Sedimentation

(d) Ultrafiltration

60. Which reaction gives colloidal solution

(a) Cu + HgCl2 CuCl

2 + Hg

(b) 2HNO3 + 3H

2S 3S + 4H

2O + 2NO

(c) 2Mg + CO2 2MgO + C

(d) Cu + CuCl2 Cu

2Cl

2

61. The correct statement in case of milk

(a) Milk is an emulsion of fat in water

(b) Milk in an emulsion of protein in water

(c) Milk is stabilized by protein

(d) Milk is stabilized by fat

62. When a colloidal solution is observed under amicroscope, we see

(a) Light scatered by colloidal particles

(b) Sol particles

(c) Shape of the particle

(d) None

63. The coagulation of sol particles or sol destructionmay be brought in by

(a) Cataphoresis

(b) Adding oppositively charged sol

(c) Adding electrolyte

(d) All

64. Foam is a colloidal solution of

(a) Gaseous particles dispersed in gas

(b) Gaseous particles dispersed in a liquid

(c) Solid particle dispersed in a liquid

(d) Solid particles dispersed in gas

65. Gold number is the index for

(a) Protective power of lyophilic colloid

(b) Purity of gold

(c) Metallic gold

(d) Electroplated gold

66. Fog is a colloidal solution of

(a) Liquid particles dispersed in gas

(b) Gaseous particles dispersed in a liquid

(c) Solid particles dispersed in a liquid

(d) Solid particles dispersed in gas


New Delhi – 110 018, Ph. : 9312629035, 8527112111

CSC – 14

67. At CMC, the surfactant molecules undergoes

(a) Association

(b) Aggregation

(c) Micelle formation

(d) All

68. In emulsion the dispersed phase and dispersionmedium are

(a) Both solids

(b) Both liquids

(c) A solid and liquid

(d) A liquid and solid

69. Brownian motion of sol particle is the......propertyof sol

(a) Electrical (b) Optical

(c) Kinetic (d) Colligative

70. A liquid which markedly scatters a beam of light(visible in dark room) but leaves no residue whenpassed through a filter paper is best described as

(a) A suspension (b) Sol

(c) True solution (d) None

71. Surface tension of lyophilic sols is

(a) Lower than H2O(b) More than H

2O

(c) Equal to H2O (d) None

72. A colloidal system in which gas is dispersed in aliquid to form bubble is known as

(a) Foam (b) Sol

(c) Aerosol (d) Emulsion

73. The outcome of internal liquid of gels on shear iscalled

(a) Synerisis (b) Thixotropy

(c) Swelling (d) None

74. Which is not lyophilic colloid

(a) Milk (b) Gum

(c) Fog (d) Blood

75. Cod liver oil is

(a) Fat dispersed in water

(b) Water dispersed in fat

(c) Water dispersed in oil

(d) Fat dispersed in fat

A N S W E R S (OBJECTIVE)

31. b

32. b

33. a

34. a

35. d

36. d

37. c

38. c

39. c

40. d

41. c

42. a

43. d

44. b

45. b

46. b

47. c

48. b

49. c

50. a

51. b

52. d

53. a

54. d

55. b

56. d

57. a

58. d

59. b

60. b

1. b

2. b

3. b

4. d

5. b

6. b

7. d

8. c

9. a

10. d

11. c

12. c

13. b

14. b

15. d

16. c

17. a

18. b

19. c

20. b

21. a

22. c

23. a

24. b

25. b

26. c

27. c

28. d

29. c

30. d

61. a

62. a

63. d

64. b

65. a

66. a

67. d

68. b

69. c

70. b

71. a

72. a

73. b

74. c

75. c

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