Download surface chemistry - einstein classes

CSC – 1
SURFACE CHEMISTRY
Syllabus :
Adsorption - Physisorption and chemisorption and
their characteristics, factors affecting adsorption of
gases on solids - Freundlich and Langmuir
adsorption isotherms, adsorption from solution.
Catalysis - Homogeneous and heterogeneous,
activity and selectivity of solid catalyst, enzyme
catalysis and its mechanism.
Colloidal state - Distinction among true solutions,
colloids and suspensions, classification of
colloids - lyophilic, lyophobic; multi molecular,
macromolecular and associated colloids (micelles),
preparation of colloids - Tyndall effect, Brownian
movement, electrophoresis, dialysis, coagulation
and flocculation; Emulsions and their
characteristics;
Einstein Classes,
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 2
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 may
consist of particles of a single macromolecule (such as protein or synthetic polymer) or an aggregate of
many atoms, ions or molecules. Colloidal particles are larger than simple molecules but small enough to
remain 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
molecules and invisible under all circumstances
Particles are visible under powerful
microscope but scattering effect by the particles
can be observed under ultra microscope
3.
Particle size is of the order of molecule size
i.e. 1mµ or 10Å or < 103 pm or < µmm
Size of particle range of diameter between 1 and
1000 nm.
4.
True solution passes easily through filter paper
as well as animal memberane or parchment
membrane
Colloidal particles passes easily through filter
paper but slowly through parchment membrane
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)
(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
Classification based on physical state of dispersed phase and dispersion medium
Eight types of colloidal syster are possible :
(solute)
Dispersed
Phase
(solvent)
Dispersed
Medium
Type of colloid
1.
Solid
Solid
Solid Sol
Coloured glasses, Gemstone, Some
alloys, minerals, rock salts.
2.
Solid
Liquid
Sol
Paints, cell fluids, starch or protein in
water, glue, gold sol, Indian ink, muddy
water, 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, cod
liver 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, lemonade
froth, beer, shaving cream, beaten egg
Einstein Classes,
Examples
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 3
If dispersion medium is water, the solution is called aquasol or hydrosal and if the dispersion medium is
alcohol, it is called alcosol and so on.
(b)
Classification based on nature of interaction between dispersed phase and dispersion medium. They
are :
Lyophilic Colloid
Lyophobic Collidal Solution
1.
Solvent attracting (If water is the dispersion
medium term used in hydrophilic
Solvent repelling (same here) i.e. if
water is the dispersion medium the
term used is hydrophobic
2.
The word lyophilic means liquid loving
The word lyophobic means liquid
hating
3.
Collidal sols directly formed by substances
like gum, gelatine, starch, rubber etc. on
mixing or warming with suitable liquid
(dispersion medium).
Subtances like metals, their sulphides
etc. when mixed simply with dispersion
medium do not form colloidal sol. They
can be prepared by special method.
4.
If dispersion medium is seperated from
dispersed phase by evaporation, the sol
can be reconstituted by simply remixing
with the dispersion medium
These sols are readily precipitated or
coagulated on the addition on the
addition of small amount of electrolytes
by heating or by shaking and hence are
not stable
5.
Thus these sols are reversible sols
Once they precipitate they do not give
back the collidal sol by simple addition
of the dispersion medium. These sols
are Irreversible.
Viscosity is much higher than dispersion medium whereas Lyophobic sol have of same as of dispersion
medium. 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 a
substance aggragate together to form species having size (with diameter less than 1 nm) e.g. Gold sol may
contain particles of various sizes having many atoms. Sulphur sol consists of particles containing a
thousand or more of S8 sulphur molecules.
2.
Macromolecular Colloid : Macro molecules have large molecular masses. These on dissolution in a
suitable solvent form a solution in which the size of the macromolecules may be in the collidal range. Such
systems are called macro-molecular colloid. These colloids are quite stable and resemble true solution in
many 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 aggregated
particles. 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” (Tk)
and above particular concentration called “Critical Micelle concentration (CMC)”. On dilution, these
colloids revert back to individual ions. e.g. surface active agents soaps, detergents belong to this class. For
soaps CMC is ~ 10–4 to 10–3 mol L–1. These colloid have both lyophilic and lyophobic part. Micelles may
contain as many as 100 molecules or more
Einstein Classes,
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 4
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. sodium
stearate) i.e. CH3(CH2)16COO–Na+ or sodium Lauryl Sulphate CH3(CH2)11SO4Na+
In
Polar part is water loving whereas non-polar part water repelling. Thus RCOO– present with COO– part in
water 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 of
molecules by double decomposition, oxidation, reduction and hydrolysis. These molecules then aggregate
leading 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 oxidising
agent like HNO3, Br2 etc. through a solution of hydrogen sulphide in water
2H2S + O2  2H2O + 2S
(ii)
By reduction : A number of metals, such as silver, gold and platinum have been obtained in colloidal state
by treating the aqueous solution of their salts with a suitable reducing agent, such as formaldehyde,
hydrazine, H2O2, SnCl2 etc.
2AuCl3 + 3SnCl2  3SnCl4 + 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 + 3H2O  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.
As2O3 + 3H2S  As2S3 + 3H2O
(b)
Dispersion Method : In these methods the coarser particles are broken to smaller particles of colloidal size
in 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 colloidal
state in the dispersion medium by grinding in a colloid mill.
(ii)
Electrical dispersion or Bredig’s Arc method : This process involve dispersion as well as
condensation. If an electric arc is struck between two electrodes of a metal like gold, silver, platinum or
copper in water having traces of an alkali, the metal is found to be converted into colloidal solution. Alkali
Act as stabliser.
Einstein Classes,
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 5
(iii)
Peptization : The process of converting precipitate into colloidal solution by shaking it with dispersion
medium in the presence of (small amount of) electrolyte. The electrolyte used for this purpose is called
peptizing agent or stablizing agent. During peptization, the precipitate absorbs one of the ions of the
electrolyte on its surface.The ion absorbed on the surface is common either with the anion or cation of the
electrolyte. This causes the development of positive or negative charge on precipitates which ultimately
break-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 FeCl3 or NH4OH
Fe(OH)3 + FeCl3  [Fe(OH)3Fe]3+ + 3Cl–
Stable solution of stannic oxide collodial is obtained by adding small amount of dilute HCl to stannic oxide
precipitate. 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 or
filtration 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 are
larger (more than 1 µ or 1000 mµ) then the size of solution particles (less than 200 mµ). But if the pores of
ordinary filter paper made smaller by soaking the filter paper in a solution of gelatin and subsequently
hardened by soaking in formaldehyde, the filter paper may retain colloidal particles and allow true solution
particle 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 a
ultra-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 retained
by 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 of
colloidal particles, mole fraction of the dispersed phase is very low. Thus value of colligative properties
determined experimentally are colligative properties determined experimentally is very low. Only osmotic
pressure 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 through
a true solution is can not be seen. When a same light is passed through a colloidal solution it become visible
as a bright streak. This phenomenon is called Tyndall effect and illuminated path (streak of light) is known
as Tyndall cone. The appearance of dust particles in a semidarkened room when a sun beam enters or when
a light is thrown from a projector in cinema hall are well known example of Tyndall effect. The dust
particles 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 constant
motion. When colloidal solutions are observed in ultramicroscope, the particles are in constant, random or
zig-zag motion, not following the definite path called as Brownian motion. Brownian movement is due to
collision of colloidal particles with dispersion medium which are in constant motion. Since colloidal
particles are heavier than dispension medium molecules their movement is considerably slower than that of
medium molecules. The mass of particle of ordinary suspension is so large that the bombardment of
molecules of the dispersion medium produces little effect and thus ordinary suspension do not exhibit
brownian movement.
Einstein Classes,
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 6
(ix)
Electrical Property : Colloidal particles are electrically charged. All the particles of a colloidal system
carry the same charge while the dispersion medium has an equal but opposite charge with the result the
system as a whole is electrically natural. Colloidal particles having similar charge, repel each other, and do
not combine to form bigger particles and thus solution is stable and particles do not settle down. When an
electric current is passed through a colloidal solution the solid particles and the liquid medium being
oppositely charged move in opposite direction. In case the experiment is so arranged that only the particles
can 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 called
electrophoretic 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 or
negative ions on their surface. When two or more ions are present in the dispersion medium differential
adsorption 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 H2S. 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 lowered
to a certain critical value or neutralised, the particles approach close enough to coalesce to form bigger
particles of the suspension range.
This phenomenon of change of colloidal state to suspension state is known as coagulation or flocculation
of 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. As2S3
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 electrolytes
with the result the charge on the sol particles is neutralised and thus these are precipitated. The ion carry
opposite charge is called Flocculating ion. e.g. The amount of electrolyte required to coagulate a fixed
amount of a sol depends upon the valency of the flocculating ion. In general, greater the valency of the
flocculating 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– > PO43– > SO42– > Cl–
Flocculating cations and anions cause coagulation (floculation) of the negatively and positively charged
colloids respectively. The minimum concentration required to cause flocculation is known as
Flocculation 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 protect
is from the action of electrolytes. This lyophilic colloids used for such purposes are known as protective
colloids. e.g. addition of gelatin (lyophilic colloid) to a gold sol (lyophobic sol) protects the latter by the
action of limited amount of NaCl. The lyophilic colloids differ in their protective powers.
Einstein Classes,
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 7
Gold Number : is used to measure the protective power of different colloids. It is defined as weight in
milligrams of a protective colloid which checks the co-agulation of 10mL of a given gold solution of adding
1 mL of a 10% solution of sodium chloride. Thus smaller the gold no. of a lyophilic colloid greater is the
protective power.
Q.
0.025 g of starch sol. is required to prevent coagulation of 10mL gol sol when 1 ml of 10% NaCl
solution 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 when
10% NaCl solution is added. Thus amount of starch required is 0.025 g i.e. 25 mg thus gold number
is 25.
There is another term called “Rubin number” which is defined as the amount of protective colloid in
milligrams which prevents the colour change in 100 mL of 0.01% congo rubic dye to which 0.16 gm
equivalent 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 in
microscope. Emulsions, particles carry a negative charge and are sensitive to addition of electrolytes. They
show Tyndall effect and Bownian movement. In most of emulsions the two liquid phases are oil and water
and 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 milk
and 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 active
agents. Industrial application of foam : (i) in ore floatation (ii) in detergency (iii) in fire fighting etc.
C8A ADSORPTION
Adsorption is defined as phenomenon of attracting & retaining the molecules on the surface of a liquid or
a 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 surface
is called adsorbate. The substance on which adsorption takes place is adsorbent e.g. charcoal, silica gel,
alumina gel, clay etc. are very good adsorbent
Absorbtion : 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
Chemisorption
H adsorption is low  20 kJ/mol
H adsorption is high ~ 200 kJ/mol
Molecule of adsorpate & adsorbent are
Held by chemical bonds
held by weak vander wall forces
Take place at low temperature & decreases
Take place at high temperature
with  T
Not very specific
Very specific
Multimolecular layer formed
Usually monomolecular layer is formed.
C8B
Einstein Classes,
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 8
1.
Freundlich Adsorption Isotherm (at temp. T)
x  Amount of Adsorbate
m  Amount of Adsorbant
kP1/n, n > 1, P  Pressure of gas adsorbed
k, n are parameter depend on nature of gas and solid.
x
 kP 1 / n
m
log
x
1
 log k  log P
m
n
value of k & n can be find out.
2.
Langmuir Adsorption Isotherm : Applicable to chemisorption
x
ap

m 1  bP
a, b  Langmuir Parameter
By reversing equation :
m 1  bP b 1 1

  .
x
aP
a a P
a, b can be calculated
Einstein Classes,
x
ap

m 1  bP
At. low pressure bp < < 1, thus
x
 aP
m
At high pressure pb > > 1, thus
x aP a


(constant)
m bP b
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 9
E X E R C I S E (OBJECTIVE)
1.
2.
3.
4.
5.
6.
7.
Which requires catalyst
(a)
X is threshold energy level
(a)
S + O2  SO2
(b)
(b)
2SO2 + O2  2SO3
(c)
C + O2  CO2
Y and Z are energy of activation for
forward and backward reaction
respectively
(d)
All
(c)
Q is heat of reaction and reaction is
exothermic
(d)
All
During hydrogenation of oils catalyst commonly
used is
8.
The catalyst used in the contact process of sulphuric
acid is
(a)
Pd or CuCl2
(b)
Finely divided Ni
(a)
Copper
(c)
Fe
(b)
Iron
(d)
V2O5
(c)
Vanadium pentoxide or Pt (asbestos)
(d)
Ni
Which is used in the Haber’s process for the
manufacture of NH3
(a)
Al2O3
(b)
Fe + Mo
(c)
CuO
(d)
Pt
9.
Which explains the effect of a catalyst on the rate
of a versible reaction
(a)
It provides a new reaction pathway with
a lower activation energy
Which is not correct for heterogeneous catalysis
(a)
The catalyst decreases the energy of
activation
(b)
It moves the equilibrium position to the
right
(b)
The surface of catalyst plays an
important role
(c)
It increases the kinetic energy of the
reacting molecules
(c)
The catalyst actually forms a compound
with reactants
(d)
It decreases the rate of the reverse
reaction
(d)
There is no change in the energy of
activation
10.
For absorption of gas on solid surface, the plots of
log x/m vs log P is linear with a slope equal to
Catalytic poisoners act by
(a)
K
(a)
Coagulating the catalyst
(b)
log K
(b)
Getting absorbed on the active centres on
the surface of catalyst
(c)
lnK
(d)
1 / n (n being integer)
(c)
Chemical combination with any one of
the reactants
(d)
None
11.
Protons accelerate the hydrolysis of esters. This is
an example of
(a)
A heterogeneous catalysis
(b)
An acid-base catalysis
(c)
A promoter
(d)
A negative catalyst
Mark the correct statement about given graph
Einstein Classes,
12.
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
Which is not true in case of catalyst
(a)
The catalyst is unchanged chemistry at
the end of a reaction
(b)
The catalyst accelerates the reaction
(c)
In a reversible reaction, the catalyst
alters the equilibrium position
(d)
A small amount of catalyst is often
sufficient to bring about a large change
in reaction
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 10
13.
14.
15.
16.
17.
18.
19.
Which type of metals form effective catalyst
20.
(a)
Alkali metals
The minimum energy level necessary to permit a
reaction to occur is
(b)
Transition metals
(a)
Internal energy
(c)
Alkaline earth metals
(b)
Threshold energy
(d)
Radioactive metals
(c)
Activation energy
(d)
Free energy
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
21.
Which is wrong in case of enzyme catalysis
(a)
Enzymes work best at an optimum
temperature
(b)
Enzymes work at an optimum pH
(c)
Enzymes are highly specific for
substrates
(d)
An enzyme raises activation energy
Air can oxidise sodium sulphite in aqueous
solution but cannot do so in the case of sodium
arsenite. If however, air is passed through a
solution containing both sodium sulphite and
sodium arsenite then both are oxidised. This is an
example of
(a)
Positive catalysis
(b)
Negative catalysis
(c)
Induced catalysis
(d)
Auto-catalysis
22.
23.
24.
The oxidation of oxalic acid by acidified KMnO4
becomes fast as the reaction progresses due to
According to Langmuir absorption isotherm the
amount 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 with
pressure
Which of the following type of catalysis can be explained by the absorption theory
(a)
Homogenous catalysis
(b)
Acid-Base catalysis
(c)
Heterogeneous catalysis
(d)
Enzyme catalysis
The reaction rate at a given temperature is slower
when
(a)
The energy of activation is higher
(b)
The energy of activation is lower
(c)
Entropy changes
(d)
Initial concentration of the reactant
remains constant
Which is not correct for catalyst. If
(a)
Enhances the rate of reaction in both
directions
(a)
Auto catalysis by Mn2+
(b)
Changes enthalpy of reaction
(b)
Presence of SO42—
(c)
Reduces activation energy of reaction
(c)
Presence of K+
(d)
Specific in nature
(d)
Presence of MnO4—
25.
Which process does not involve a catalyst
Which is universally correct for the catalyst
(a)
Haber’s process
(a)
Initiates reaction
(b)
Thermite process
(b)
Does not initiate reactions
(c)
Ostwald’s process
(c)
Does not alter the nature of products
(d)
Contact process
(d)
Is not specific in nature
The catalyst iron, employed in the Haber’s process,
contains molybdenum, the function of which is
(a)
To increase the rate of combination of
gases
(b)
To counterbalance for the presence of
impurities in the gases
(c)
To act as a catalyst promoter and increase
activity of catalyst
(d)
To make up for the adverse temperature
and pressure conditions
Einstein Classes,
26.
Which plot is the absorption isobar for
chemisorption where X is the amount of gas
absorbed on mass m (at constant pressure) at
temperature T.
(a)
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 11
30.
(b)
31.
(c)
32.
(d)
27.
28.
33.
In the titration between oxalic acid and acidified
potassium permanganate, the manganous salt
formed 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
Which equation represents Freundlisch absorbtion
isotherm (physical adsorption is basis of this theory)
(a)
x
 K (P )1/ n where x is amount of gas
m
34.
35.
36.
absorbed on mass ‘m’ at pressure P
x
1
 log K  log P
m
n
(b)
log
(c)
x
x
 KP at low pressure and
K
m
m
at high pressure
(d)
29.
All
The function of negative catalyst is
(a)
To remove the active intermediate from
the reaction
(b)
To terminate the chain reaction
Einstein Classes,
37.
(c)
Both (a) and (b)
(d)
None
Zeolites
(a)
Are microporous aluminosilicates
(b)
Have general formula Mx/n [(AlO2)x
(SiO2)4].mH2O
(c)
Have pore sizes between 260 pm to
740 pm
(d)
All
The phenomenon in which absorption and
absorption takes place simultaneously is called
(a)
Desorption
(b)
(c)
Both (a) and (b) (d)
Sorption
None
The extend of absorption of a gas on a solid
depends on
(a)
A nature of gas
(b)
Pressure of gas
(c)
Temperature of the system
(d)
All
An increase in the concentration of absorbate at
the surface relative to its concentration in bulk
phase is called
(a)
Adsorption
(b)
Enthalpy
(c)
Absorption
(d)
None
On adding few drops of dil. HCl or FeCl3 to freshly
precipitated ferric hydroxide, a red coloured
collodial solution is obtained. This phenomenon is
known as
(a)
Preptization
(b)
Dialysis
(c)
Protection
(d)
Dissolution
Which is not shown by sols
(a)
Adsorption
(c)
Flocculation
(d)
Paramagnetism
(b)
Tyndall effect
The arsenious sulphide sol has negative charge. The
maximum coagulating power for precipitating it is
of
(a)
0.1 N Zn (NO3)2 (b)
0.1 N Na3PO4
(c)
0.1 N ZnSO4
0.1 N AlCl3
(d)
Lyophilic sols are more stable than lyophobic sols
because
(a)
The collodial particles have positive
charge
(b)
The collodial particles have no charge
(c)
The collodial particles are solvated
(d)
There are strong electrostatic repulsions
between the negatively charged collodial
particles.
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 12
38.
39.
40.
Which forms a collodial solution in water
(c)
10–7 cm to 10–10 cm
(a)
NaCl
(b)
Glucose
(d)
10–1 cm to 10–2 cm
(c)
Starch
(d)
Barium nitrate
Collodial solution of arsenious sulphide can be
prepared by
The separation of collodial particles
(or purification of sol) from particles of molecular
dimensions is known as
(a)
Electrodispersion method
(a)
Photolysis
(b)
Dialysis
(b)
Peptization
(c)
Pyrolysis
(d)
Peptization
(c)
Double decomposition
(d)
Hydrolysis
42.
(a)
The amount of gold present in the
colloid
(b)
The amount of gold required to break the
colloid
(c)
The amount of gold required to protect
the colloid
(a)
To prevent the formation of a colloid
(b)
To stabilize the colloid and prevent
crystal growth
(c)
To cause the mixture of solidify
(d)
To improve the flavour
Preptization is a process of
Precipitating colloidal particles
None of the above
(b)
Purifying colloidal particles
Collodial solutions are not purified by
(c)
Dispersing the precipitate into colloidal
state
(d)
None
(a)
Dialysis
(b)
Electrodialysis
(c)
Electrophoresis (d)
Ultrafiltration
48.
Gold number :
(b)
(c)
(d)
44.
47.
Gelatin is often used as an ingredient in the
manufacture of ice-cream. The reason for this is
(a)
(a)
43.
46.
Gold number gives
(d)
41.
45.
May be defined as the milligram of the
dry material of which the hydrophilic sol
is prepared and which when added to
10 mL of red gold sol, will prevent it from
coagulation on the addition of 1 mL of
10 per cent sodium chloride solution
49.
May be defined as the milligram of the
dry material of which the hydrophilic sol
is prepared and which when added to
1 mL of red gold sol, will prevent it from
coagulation on the addition of 10 mL of
10 per cent sodium chloride solution
May be defined as the milligram of the
dry material of which the hydrophilic sol
is prepared and which when added to
1 mL of red gold sol, will prevent it from
coagulation on the addition of 1 mL of
1 per cent sodium chloride solution
50.
None of the above
51.
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
Gold number of a lyophilic sol refers that
(a)
Larger is its value, the greater is the
peptizing power
(b)
Lower is its value, the greater is the
peptizing power
(c)
Lower is its value, the greater is the
protecting power
(d)
Larger is its value, the greater is the
protecting power
Gold number is minimum in case of
(a)
Gelatin
(b)
Egg albumin
(c)
Gum arabic
(d)
Starch
(a)
Electro deposition
When dilute aqueous solution of AgNO3 (excess) is
added to KI solution, positively charged sol
particles of AgI are formed due to absorption of
ion
(b)
Electrodialysis
(a)
K+
(b)
Ag+
(c)
—
(d)
NO3—
The movement of sol particles under an applied
electric field is called
(c)
Electro-osmosis
(d)
Electrophoresis
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
Einstein Classes,
52.
I
The charge on As2S3 sol is due to the absorption of
(a)
H+
(b)
OH—
(c)
O 2—
(d)
S2—
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 13
53.
The Rubin number which was proposed by Ostwald
as an alternative to the Gold number in order to
measure the protective efficiency of a lyophilic
colloid may be defined as the
(a)
(b)
(c)
(d)
54.
55.
56.
57.
58.
Mass is milligram of a colloid per 100 mL
of solution which just prevents the
colour change of standard sol of dye
Congo-Rubin from red to violet when
0.16 g eq. KCl is added to it
Mass in gram of a colloid per 100 mL of
solution which just prevents the colour
change of standard sol of dye
Congo-Rubin from red to violet when
0.1 M KCl is added to it
59.
60.
61.
Mass in gram of a colloid per 100 mL of
solution which just prevents the colour
changed of standard sol of dye
Congo-Rubin from red to violet when
0.2 M KCl is added to it
Mass in gram of a colloid per 100 mL of
solution which just prevents the colour
change of standard sol of dye
Congo-Rubin from red to violet when
1 M KCl is added to it
62.
If dispersion medium is water, the colloidal system
is called
(a)
Sol
(b)
Aerosol
(c)
Organosol
(d)
Aquasol
63.
The property of colloidal suspension used to
determine the nature of charge on the particles is
(a)
Dialysis
(b)
Electrophoresis
(c)
Sedimentation
(d)
Ultrafiltration
Which reaction gives colloidal solution
(a)
Cu + HgCl 2  CuCl2 + Hg
(b)
2HNO3 + 3H2S  3S + 4H2O + 2NO
(c)
2Mg + CO2  2MgO + C
(d)
Cu + CuCl2  Cu2Cl2
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
When a colloidal solution is observed under a
microscope, we see
(a)
Light scatered by colloidal particles
(b)
Sol particles
(c)
Shape of the particle
(d)
None
The coagulation of sol particles or sol destruction
may be brought in by
Lyophobic colloids are
(a)
Cataphoresis
(a)
Reversible colloids
(b)
Adding oppositively charged sol
(b)
Irreversible colloids
(c)
Adding electrolyte
(c)
Protencitve colloids
(d)
All
(d)
Gum, proteins
64.
Foam is a colloidal solution of
Which is not related with colloids
(a)
Gaseous particles dispersed in gas
(a)
Brownian movement
(b)
Gaseous particles dispersed in a liquid
(b)
Dialysis
(c)
Solid particle dispersed in a liquid
(c)
Ultrafiltration
(d)
Solid particles dispersed in gas
(d)
Wavelength
65.
Gold number is the index for
Flocculation value is expressed in terms of
(a)
Protective power of lyophilic colloid
(a)
Millimole per litre
(b)
Purity of gold
(b)
Mol per litre
(c)
Metallic gold
(c)
Gram per litre
(d)
Electroplated gold
(d)
Mol per millilitre
66.
(a)
Liquid particles dispersed in gas
Cane sugar
(b)
Gaseous particles dispersed in a liquid
Blood
(c)
Solid particles dispersed in a liquid
(d)
Solid particles dispersed in gas
Which one is a colloid
(a)
(c)
Urea
(b)
Sodium chloride (d)
Einstein Classes,
Fog is a colloidal solution of
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111
CSC – 14
67.
68.
69.
70.
71.
72.
73.
74.
75.
At CMC, the surfactant molecules undergoes
A N S W E R S (OBJECTIVE)
(a)
Association
(b)
Aggregation
(c)
Micelle formation
(d)
All
In emulsion the dispersed phase and dispersion
medium are
1.
b
31.
b
61.
a
2.
b
32.
b
62.
a
3.
b
33.
a
63.
d
(a)
Both solids
(b)
Both liquids
4.
d
34.
a
64.
b
(c)
A solid and liquid
5.
b
35.
d
65.
a
(d)
A liquid and solid
6.
b
36.
d
66.
a
7.
d
37.
c
67.
d
8.
c
38.
c
68.
b
A liquid which markedly scatters a beam of light
(visible in dark room) but leaves no residue when
passed through a filter paper is best described as
9.
a
39.
c
69.
c
10.
d
40.
d
70.
b
(a)
A suspension
(b)
Sol
11.
c
41.
c
71.
a
(c)
True solution
(d)
None
12.
c
42.
a
72.
a
13.
b
43.
d
73.
b
14.
b
44.
b
74.
c
15.
d
45.
b
75.
c
16.
c
46.
b
17.
a
47.
c
18.
b
48.
b
19.
c
49.
c
20.
b
50.
a
21.
a
51.
b
Cod liver oil is
22.
c
52.
d
(a)
Fat dispersed in water
23.
a
(b)
Water dispersed in fat
53.
a
(c)
Water dispersed in oil
24.
b
54.
d
(d)
Fat dispersed in fat
25.
b
55.
b
26.
c
56.
d
27.
c
57.
a
28.
d
58.
d
29.
c
59.
b
30.
d
60.
b
Brownian motion of sol particle is the......property
of sol
(a)
Electrical
(b)
Optical
(c)
Kinetic
(d)
Colligative
Surface tension of lyophilic sols is
(a)
Lower than H2O(b)
More than H2O
(c)
Equal to H2O
None
(d)
A colloidal system in which gas is dispersed in a
liquid to form bubble is known as
(a)
Foam
(b)
Sol
(c)
Aerosol
(d)
Emulsion
The outcome of internal liquid of gels on shear is
called
(a)
Synerisis
(b)
Thixotropy
(c)
Swelling
(d)
None
Which is not lyophilic colloid
(a)
Milk
(b)
Gum
(c)
Fog
(d)
Blood
Einstein Classes,
Unit No. 102, 103, Vardhman Ring Road Plaza, Vikas Puri Extn., Outer Ring Road
New Delhi – 110 018, Ph. : 9312629035, 8527112111