process of converting precipitate into colloidal solution

process of converting a colloidal solution into precipitate

process of converting soluble particles to form colloidal solution

process of bringing colloidal molecule into solution

MCQ Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 1

A particular adsorption process has the following characteristics : (i) It arises due to van der Waals forces and (ii) it is reversible. Identify the correct statement that describes the above adsorption process :

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Adsorption is monolayer
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Energy of activation is low
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Adsorption increases with increase in temperature
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Enthalpy of adsorption is greater than 100 kJ mol $^{-1}$

Explanation

Physical adsorption process (physisorption) has the following characteristics : (i) It arises due to van der Waals forces and (ii) it is reversible. The correct statement that describes the above adsorption process is option B. Energy of activation for physisorption is low.
Physisorption is multilayer. It decreases with increase in temperature and the enthalpy of physisorption is low

$(20-40$ kJ/mol

$)$ .

The most appropriate method of making egg-albumin sol is:

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Break an egg carefully and transfer the transparent part of the content to 100 mL of 5% w/V saline solution and stir well.
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Keep the egg in boiling water for 10 minutes. After removing the shell, transfer the white part of the content to 100 mL of 5% w/V saline solution and homogenize with a mechanical shaker.
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Keep the egg in boiling water for 10 minutes. After removing the shell, transfer the yellow part of the content to 100 mL of 5% w/V saline solution and homogenize with a mechanical shaker
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Break an egg carefully and transfer only the yellow part of the content to 100 mL of 5% w/V saline solution and stir well.

Explanation

The most appropriate method of making egg-albumin solution is by breaking an egg carefully and transfer the transparent part of the content to 100 mL of

$5$ % w/V saline solution and stir well.

Note: Egg-albumin is the transparent part of the egg. During the preparation of the solution, water should be cold. If we boil water, the solution will be coagulated.

Peptization is a :

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process of converting a colloidal solution into precipitate
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process of converting precipitate into colloidal solution
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process of converting soluble particles to form colloidal solution
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process of bringing colloidal molecule into solution

The moles of

$HCl$ required to neutralise left

$N{H}_{3}$ solution after adsorption is:

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$0.123$
0%
$0.175$
0%
$0.145$
0%
$0.153$

Explanation

Total moles of

$N{H}_{3}$ adsorbed on surface

$=\displaystyle\frac{1.415\times {10}^{22}}{6.023\times {10}^{23}} =0.0235$ .

Moles of

$N{H}_{3}$ before adsorption

$=\displaystyle\frac{100\times 2}{1000}= 0.2$ .
So, moles of

$N{H}_{3}$ left after adosrption

$=$ moles of

$HCl$ required

$= 0.2 - 0.0235 = 0.175$ .

Mention catalyst in the following reaction:

$KClO_3 \rightarrow KCl + O_2$

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$MnO_2$
0%
$FeCl_3$
0%
$PdCl_2$
0%
$ZnO/CuO$

Explanation

Option (A) is correct.

The catalyst used for the reaction

$KClO_3 \rightarrow KCl + O_2$ reaction is

$MnO_2$ .The

$MnO_2$ , causes the reaction to take place more rapidly at a lower temperature.

The given reaction is a decomposition reaction of potassium chlorate used to obtain oxygen.

Which is correct in case of heterogeneous catalyst?

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The catalyst decreases the energy of active ion.
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The surface of catalyst plays an important role.
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The catalyst actually forms a compound with reactants.
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There is no change in the energy of activation.

Substances, which are added to soaps change their properties in order to make them more useful for a particular application, are called ___.

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fillers
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absorbant
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reagent
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none

A freshly obtained precipitate of

$SnO_2$ is peptized by little of

$KOH$ to give a sol. The sol particles may be represented as :

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$[SnO_2]K^{+}$
0%
$[SnP_2]OH^{-}$
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$[SnO_2]Sn^{4+}$
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$[SnO_2]SnO_3^{2-}$

Explanation

The reaction is as follows:

$SnO_2(s)+2KOH(aq)\rightarrow K_2SnO_3(aq)+H_2O$

$SnO_3^{2-}$ ions would be preferentially adsorbed by

$SnO_2$ particles.

Milk is an example of :

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Aquasol
0%
True solution
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Aerosol
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Emulsion

Explanation

Aerosols are a colloidal solution of liquid and gas.

A true solution is a homogeneous solution in which the solute particles have diameters less than

$10^{-7}$ cm.

In an emulsion, one liquid (the dispersed phase) is dispersed in the other liquid (the continuous phase).

Hence, milk is an example of emulsion.

Which of the following is homogeneous?

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Milk
0%
Paint
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Shampoo
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All of the above

Explanation

The emulsion is a colloidal system consisting of immiscible liquids.

Milk is an example of emulsion in which particles of liquid fat are dispersed in water. In common occurrence, however, one of the liquids is water and the other, and oily substance insoluble in it. The suspended droplets are larger than the particles of the sols. It is because of the density differences between the phases being small.

Hence, the correct option is

$A$

The process of passing of a precipitate into colloidal solution on adding an electrolyte is called

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dialysis
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peptization
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electophoresis
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electro-osmosis

Sorption is the term used when :

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adsorption takes place
0%
absorption takes place
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both adsorption and absorption take place
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desorption takes place

Assertion : Physical adsorption of molecules on the surface requires activation energy.
Reason : The bonds of adsorbed molecules are broken.

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Both Assertion and Reason are correct and Reason is the correct explanation of Assertion
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Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion
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Assertion is correct but reason is incorrect
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Assertion is incorrect but reason is correct
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Both Assertion and Reason are incorrect

Intermediate compound formation theory explains:

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homogeneous catalysis
0%
heterogeneous catalysis
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both of the above
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none of the above

There is desorption of physical adsorption when :

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temperature is increased
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temperature is decreased
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pressure is increased
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concentration is increased

The metal used as a catalyst in the hydrogenation of oils is:

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sodium
0%
nickel
0%
mercury
0%
manganese

Explanation

$Ni$ as catalyst binds both the $H_2$ and the unsaturated substrate and facilitates their union which is the mechanism of hydrogenation of oil while other given element can't able to do so.

$Ni$ is used for most reaction as the catalyst because of it is cheaper to run the reaction with it, in commercial world cost-effectiveness is best and desired pathway.

The ______ colloidal dispersions are called emulsions.

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liquid-liquid
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solid-solid
0%
gas-gas
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A and C

The adhering of the molecules of gas on the surface of a solid is called _______ _.

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mixture
0%
adsorption
0%
reduction
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none of these

A catalyst is a substance which:

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increases the average kinetic energy of reacting molecules
0%
alters the reaction mechanism
0%
increases the frequency of collisions of reaction species.
0%
None of these

Explanation

The two main ways catalysts affect chemical reactions are by creating a way to lower activation energy or by changing how the reaction happens.

Therefore, they can lower the energy of the transition state, so the overall activation energy needed for the reaction decreases.

They can alter the mechanism of a reaction and thus change the transition state.

Hence, option

$B$ is correct.

Pesticides & insecticides are available in the form of :

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powders
0%
sprays
0%
emulsions
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all of these

On adding dilute

$HCl$ to chalk piece,

${CO}_{2}$ is evolved. This is an example of:

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a hetrogeneous reaction
0%
an acid-base reaction
0%
an oxidation-reduction reaction
0%
catalysed reaction

Explanation

Heterogeneous reactions are chemical reactions in which the reactants and products are in a different phase.

Dilute

$HCl$ is a liquid, chalk piece is solid. Both react with each other to form

$CO_2$ gas. So this reaction is a heterogeneous reaction.

$2HCl(l) + CaCO_3(s)\rightarrow CaOCl_2(s) + CO_2(g)$

Hence, option

$A$ is correct.

In the presence of a catalyst, the heat evolved or absorbed during the reaction:

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increases
0%
decreases
0%
remains unchanged
0%
may increase or decrease

Which of the following is incorrect for physisorption?

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Reversible
0%
Increases with increase in temperature
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Low heat of adsorption
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Increases with increase in surface area

Which of the following metals adsorb hydrogen?

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Zn
0%
Pd
0%
Pt
0%
K

A colloidal sol can be prepared by:

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breaking the bulky substance into fine particles of colloidal dimensions
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increasing the size of molecular particles to form larger aggregates.
0%
mixing a substance directly with a dispersion medium
0%
all of the above

An emulsion is a colloidal solution of:

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two solids
0%
two liquids
0%
two gases
0%
one solid and liquid

Emulsifying agent is used for:

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precipitation of am emulsion
0%
denaturation of an emulsion
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stabilization of an emulsion
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oxidation of an emulsion

The principal emulsifying agent for w/o emulsion is:

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proteins
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gum
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lamp black
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synthetic soaps

The emulsifying agent used in o/w emulsion is:

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protein
0%
long chain alcohol
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lampblack
0%
heavy metal salts of fatty acids

When soap or detergent dissolves in water, which of the following is true?

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The polar water soluble ( hydrophilic) head is on the surface of the micelle whereas non polar oil soluble (hydrophobic) tail is in the center of the micelle.
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The polar water soluble ( hydrophilic) head is in the center of the micelle whereas non polar oil soluble (hydrophobic) tail is on the surface of the micelle.
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The polar water soluble ( hydrophilic) head is in the center of the micelle.
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Non polar oil soluble (hydrophobic) tail is on the surface of the micelle.

Which of the following is true when soap or detergent is added to water?

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The anions of emulsion repel each other hence do not precipitate.
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The anions of emulsion attract each other hence do not precipitate.
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The anions of emulsion repel each other hence precipitate.
0%
The anions of emulsion attract each other hence precipitate.

Peptisation involves :

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precipitation of colloidial particles
0%
disintegration of colloidal aggregates
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evaporation of dispersion medium
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impact of molecules of the dispersion medium on the colloidal particles

The colloidal sol found effective in the treatment of eye disease is:

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colloidal sulphur
0%
colloidal antimony
0%
colloidal silver
0%
colloidal gold

Physical adsorption is appreciable at:

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higher temperature
0%
lower temperature
0%
room temperature
0%
$100^oC$

The homogeneous catalysts is shown by:

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Haber's process, ${ N }_{ 2 }+3{ H }_{ 2 }\xrightarrow [ ]{ Fe } 2{ NH }_{ 3 }$
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Ostwald process, $4{ NH }_{ 3 }+5{ O }_{ 2 }\xrightarrow [ ]{ Pt } 4NO+6{ H }_{ 2 }O$
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Contact process, $\quad 2S{ O }_{ 2 }+{ O }_{ 2 }\xrightarrow [ ]{ V_{2}O_{5}} 2S{ O }_{ 3 }$
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$2{ C }_{ 2 }{ H }_{ 5 }OH\xrightarrow [ ]{ { H }_{ 2 }{ SO }_{ 4 } } { C }_{ 2 }{ H }_{ 5 }-O-{ C }_{ 2 }{ H }_{ 5 }+{ H }_{ 2 }O$

Explanation

If the catalyst is present in the same phase as the reactants, it is called homogeneous catalyst and this type of catalysts is called homogeneous catalysis. For example:

$2{ C }_{ 2 }{ H }_{ 5 }OH(aq)\xrightarrow [ ]{ { H }_{ 2 }{ SO }_{ 4 } } { C }_{ 2 }{ H }_{ 5 }-O-{ C }_{ 2 }{ H }_{ 5 }(aq)+{ H }_{ 2 }O(l)\quad$
Here, both reactants and catalyst are present in the liquid phase.

Platinised asbestos is used as a catalyst in, the manufacture of

$H_2SO_4$ . It is an example of:

0%
homogeneous catalyst
0%
heterogeneous catalyst
0%
autocatalyst
0%
induced catalyst

Explanation

Platinised asbestos is a solid catalyst whereas the reactants

$SO_2$ and

$O_2$ and product

$SO_3$ are in gas phase in the manufacture of sulfuric acid. So the above process is heterogeneous catalysis.

Hence option B is correct.

TEL minimises the knocking effect when mixed with petrol. It acts as:

0%
positive catalyst
0%
negative catalyst
0%
autocatalyst
0%
induced catalyst

Explanation

Tetraethyl lead is added to petrol as it increases the octane number of petrol and it will result in a decrease in knocking activity(negative catalyst) of engine piston.

Hence option $B$ is correct.

Which one of the following statements is incorrect in the case of heterogeneous catalyst?

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The catalyst lowers the energy of activation.
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The catalyst actually forms a compound with the reactant.
0%
The surface of the catalyst plays a very important role.
0%
There is no change in the energy of activation.

Which of the following acts as a negative catalyst?

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Lead tetraethyl as antiknock compound
0%
Glycerol in decomposition of $H_2O_2$
0%
Ethanol in the oxidation of chloroform
0%
All of the above

Explanation

An Negative Catalyst is a substance that decreases the rate of a chemical reaction.

Lead tetraethyl as antiknock compound

Glycerol in decomposition of

$H_2O_2$

Ethanol in the oxidation of chloroform

All are act as Negative catalyst.

A poisonous gas is adsorbed at activated charcoal. The activated charcoal is:

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absorber
0%
adsorbate
0%
adsorbent
0%
absorbate

Protons accelerate the hydrolysis of esters. This is an example of a/an:

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promoter
0%
homogeneous catalyst
0%
acid-base catalyst
0%
autocatalyst

Explanation

Hydrolysis of esters is catalyzed by protons.

The proton is the most efficient homogeneous catalyst ,because Water forms protons by the process of self-ionization of water.Acids accelerate (catalyze) the hydrolysis of esters:

$CH_3CO_2CH_3 + H_2O\rightarrow CH_3CO_2H + CH_3OH$

Which statement is not correct?

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Physical adsorption is due to van der Waals forces.
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Physical adsorption decreases at high temperature and low pressure.
0%
Physical adsorption is reversible.
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Adsorption energy for chemical adsorption is generally lesser than that for physical adsorption.

Which type of phenomenon is used when coloured dye is removed from solution of sugar by charcoal?

0%
Absorption
0%
Adsorption
0%
Both absorption and adsorption
0%
None of the above

Explanation

Absorption is the process in which a fluid is dissolved by a liquid or a solid (absorbent). Adsorption is the process in which atoms, ions or molecules from a substance (it could be gas, liquid or dissolved solid) adhere to a surface of the adsorbent.

Charcoal is used as a decolourizer as it adsorbs the colouring matter from the coloured solution of sugar.

Hence, the correct option is $\text{B}$

Which of the following reactions is an example for homogeneous catalysis :

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$2H_2O_2(l)\xrightarrow{MnO_2(s)} 2H_2O (l)+O_2(g)$
0%
$2SO_2(g)+O_2(g)\xrightarrow{V_2O_5(s)} 2SO_3(g)$
0%
$2CO(g) +O_2(g) \xrightarrow{NO(g)} 2CO_2(g)$
0%
$H_2(g) +C_2H_4(g) \xrightarrow{Ni(s)} C_2H_6(g)$

Which of the following statements is NOT TRUE in respect of hydrophilic sols?

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They are quite stable and are not easily coagulated
0%
There is considerable interaction between dispersed phase and dispersion medium (water)
0%
The sol particles are hydrated
0%
They are very sensitive to coagulation by a small concentration of electrolytes

For the adsorption of a gas on a solid, the plot of log (x/m) versus log P linear with slope equal to:

0%
K
0%
log k
0%
N
0%
$\dfrac { 1 }{ n }$

In which emulsion coloured droplets are obtained when oil soluble dye is added to it?

0%
Cod liver oil
0%
Cold cream
0%
Hair cream
0%
Milk

Which statement is incorrect for a catalyst?

0%
It does not affect the equilibrium constant
0%
It increases the proportion of products in less time
0%
It decreases the activation energy of a reaction
0%
It increases the free energy change for the reaction

The graph between log

$\dfrac { X }{ m }$ v/s log P is straight-line inclined at an angle

$45^o$ with intercept 0.What will be the rate of adsorption at pressure of 0.4 atm?

0%
0.4
0%
0.6
0%
0.8
0%
0.9

Explanation

Slope in equation is $\dfrac{1}{n}$ = tan $45^o$ =1
Intercept is logk = 0.30, that implies k=2

Hence by equation $\dfrac{x}{m} = kp^{1/n}$

k=2, n=1 and p=0.4

$\therefore$ Rate of adsorption, x/m is 0.8.

Option C is correct.

Which of the following catalysis is an example of negative catalysis?

0%
$\displaystyle 2SO_2 + O_2 \overset{V_2O_5}{\longrightarrow} 2SO_3$
0%
$\displaystyle CHCl_3 + O_2 \overset{alcohol}{\longrightarrow} 2COCl_2 + 2HCl$
0%
$\displaystyle 2KClO_3 \overset{MnO_2}{\underset{\Delta}{\longrightarrow}} 2KCl + 3O_2$
0%
$\displaystyle CO + 3H_2 \overset{Ni}{\longrightarrow} CH_4 + H_2O$

Explanation

Catalyst alters the rate of reaction by altering activation energy of reaction.

It could be positive catalyst which increases rate and can be negative catalyst which decreases rate of reaction.

According to the given options A, C, D have positive catalysts but in option B alcohol (

$C_2H_5OH$ ) is a negative catalyst for oxidation of

$CHCl_3$ which prevents reaction of chloroform with oxygen to give

$COCl_2$ .

CBSE Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 1 - MCQExams.com

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Practice Class 12 Engineering Chemistry Quiz Questions and Answers

CBSE Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 1 - MCQExams.com

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Practice Class 12 Engineering Chemistry Quiz Questions and Answers

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