MCQ Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 3

Activated charcoal is used to remove colouring from pure substances. It works by

0%
Oxidation
0%
Reduction
0%
Bleaching
0%
Adsorption

Which of the following colloids are formed when hydrogen sulphide gas is passed through a cold solution of arsenious oxide?

0%
$As_{2}S_{3}$
0%
$As_{2}O_{3}$
0%
$As_{2}S$
0%
$As_{2}H_{2}$

Explanation

It is due to adsorption of

S^{2 -}

$S^{2-}$ ions on the surface of the colloidal particles and

H^{+}

$H^{+}$ ions in the diffused layer.

Option A is correct.

In Bredig's arc method some alkali is added because_____

0%
It increase electrical conductance
0%
To obtain molecular colloid
0%
To obtain colloidal particles of same size
0%
To stabilise the sol

Animal charcoal is used in decolourising colour of liquids because it is a good_________

0%
Adsorbate
0%
Adsorbent
0%
Oxidising agent
0%
Reducing agent

In adsorption of oxalic acid on activated charcoal, the activated charcoal is known as:

0%
Adsorbent
0%
Absorbate
0%
Adsorber
0%
Absorber

Which of the following is not an emulsion?

0%
Butter
0%
Ice cream
0%
Milk
0%
Cloud

Hydrophilic sols are________

0%
Reversible
0%
Irreversible
0%
Unstable
0%
None of these

Cod liver oil is

0%
An emulsion
0%
Solution
0%
Colloidal solution
0%
Suspension

The decomposition of

H_{2} O_{2}

$H_{2}O_{2}$ can be slows down by the addition of small amount of phosphoric acid which act as_________

0%
Promoter
0%
Inhibitor
0%
Detainer
0%
Stopper

Reagent (C) is:

0%
$Me_2Cd$
0%
$Me_2CuLi$
0%
$CH_3I$
0%
$Me_2SO_4 + NaOH$

Catalyst used in dimerisation of acetylene to prepare chloroprene is

0%
$HgSO_{4} + H_{2}SO_{4}$
0%
$Cu_{2}Cl_{2}$
0%
$Cu_{2}Cl_{2} + NH_{4}Cl$
0%
$Cu_{2}Cl_{2} + NH_{4}OH$

Explanation

Acetylene dimerized to give vinyl acetylene when it combines with hydrogen chloride to form 4-chloro-1, 2-butadiene, an allene derivative, which in presence of cuprous chloride (

C u_{2} C l_{2}

$Cu_2Cl_2$ ) and ammonium chloride (

N H_{4} C l

$NH_4Cl$ ), rearranges to form

2- Chlorobuta-1 , 3-diene

$\text{2- Chlorobuta-1 , 3-diene}$ .

1645071_1765604_ans_6345feaf35074fd6b40a890ddc5921bd.png

Two percent of ethanol is added during the oxidation of chloroform to stop the formation of carbonyl chloride. In this reaction ethanol acts as

0%
Auto catalyst
0%
Negative catalyst
0%
Positive catalyst
0%
None of thewse

Explanation

Any substance which when added to a chemical reaction inhibit or decrease the rate of reaction is called negative catalyst. In

C H C l_{3}

$CHCl_3$ when two percent ethanol is added , it stops the formation of carbonyl chloride. So ethanol acts as negative catalyst.

An emulsifier is a substance which____________

0%
stabilises the emulsion
0%
homogenises the emulsion
0%
coagulates the emulsion
0%
retards the dispersion of liquid in liquid

In a reaction, catalyst changes ___________

0%
physically
0%
qualitatively
0%
chemically
0%
quantitatively

An emulsion can not be broken by _______ and _________

0%
heating
0%
adding more amount of dispersion medium
0%
freezing
0%
adding emulsifying agent

Which of the following substances will precipitate the negatively charged emulsions?

0%
KCl
0%
glucose
0%
urea
0%
NaCl

Explanation

Negatively charged emulsion can be precipitated by the oppositely charged electrolyte. $\mathrm{Na}^{+}$ and $\mathrm{K}^{+}$ from the electrolyte can neutralize the negatively charge emulsion and precipitate the colloid.

Hence, options "A" & "D" are correct answers.

Which of the following options are correct?

0%
Micelle formation by soap in aqueous solution is possible at all temperatures.
0%
Micelle formation by soap in aqueous solution occurs above a particular concentration.
0%
On dilution of soap solution micelles may revert to individual ions.
0%
Soap solution behaves as a normal strong electrolyte at all concentrations.

Explanation

The formation of micelles takes place only above a particular temperature called Kraft temperature $\left(\mathrm{T}_{\mathrm{k}}\right)$ and above a
particular concentration called critical micelle concentration (CMC). On dilution, these colloids revert back to individual ions.

Hence, Options "B" & "C" are correct answers.

Emulsions can be destroyed by:

0%
the addition of emulsifier which tends to form another emulsion
0%
electrophoresis with high potential
0%
filltaration
0%
all of the above

Explanation

Electrophoresis is a technique commonly used in the lab to separate charged molecules.

$\text{Electrophoresis is a technique commonly used in the lab to separate charged molecules.}$

Soaps do not create water pollution because:

0%
soaps are insoluble in water
0%
soaps are soluble in water
0%
soaps are fairly bio-degradable
0%
soaps are non-biodegradable

Which of the following is the emulsion of water in oil?

0%
Buttermilk
0%
Milk
0%
Cold cream
0%
Vanishing cream

In a reversible reaction, a catalyst used

0%
Increases the speed of the forward reaction
0%
Decreases the speed of the backward reaction
0%
Does not alter the final state of equilibrium
0%
Increases the amount of the product formed

An oil-soluble dye is mixed with emulsion and the emulsion remains colourless. Then, it is :

0%
oil in water emulsion
0%
water in oil emiulsion
0%
oil in oil emulsion
0%
water in water emulsion

Which is not a characteristic of a catalyst

0%
It changes the equilibrium constant
0%
It alters the reaction path
0%
It increases the rate of reaction
0%
It increases the average K.E. of the molecules

Soap removes grease by:

0%
adsorption
0%
emulsification
0%
coagulation
0%
none of these

Explanation

Soap is an excellent cleanser because of its ability to act as an emulsifying agent. An emulsifier is capable of dispersing one liquid into another immiscible liquid. This means that while oil (which attracts dirt) doesn't naturally mix with water, soap can suspend oil/dirt in such a way that it can be removed.

Grease and oil are nonpolar and insoluble in water. When soap and soiling oils are mixed, the nonpolar hydrocarbon portion of the micelles breaks up the nonpolar oil molecules. A different type of micelle then forms, with nonpolar soiling molecules in the centre. Thus, grease and oil and the 'dirt' attached to them are caught inside the micelle and can be rinsed away.

Hence, the correct option is

B

$\text{B}$

Milk is an example of:

0%
emulsion
0%
suspension
0%
foam
0%
sol

Hydrophobic is another name for a substance which:

0%
bonds weakly to oil
0%
bonds weakly to water
0%
repels oil
0%
attracts water

Water which gives lather with soap easily is called as hard water.

0%
True
0%
False

Explanation

Hard water is the water that contains salts of calcium and magnesium principally as bicarbonates, chlorides, and sulfates. When soap is added to hard water, the

C a^{2 +}

$Ca^{ 2+ }$ and

M g^{2 +}

$Mg^{ 2+ }$ ions present in hard water react with soap. The sodium salts present in soaps are converted to their corresponding calcium and magnesium salts which are precipitated as scum. Therefore hard water do not form lather with soap.

option B is correct

The activation energy of a catalysed reaction is more than the activation energy of the uncatalysed reaction.

0%
True
0%
False

The polar end in soap is called :

0%
hydrophilic
0%
hydrophobic
0%
lipophilic
0%
none of these

Carbocation having more stability is :

0%
$1^0 carbocation$
0%
$2^0 carbocation$
0%
$3^0 carbocation$
0%
$none$

What is the function of germ pore ?

0%
Absorption of water for seed germination
0%
Initiation of pollen tube
0%
Release of male gametes
0%
Release of female gametes

Explanation

A germ pore is a small pore in the outer wall of fungal pore which is used for initiation of pollen tube.

$\text{A germ pore is a small pore in the outer wall of fungal pore which is used for initiation of pollen tube.}$

Temporary hardness can be removed by mixing water with slaked lime, this process is known as softening of water.

0%
True
0%
False

Explanation

Removal of hardness from water can be done by using different methods that can be grouped into two: chemical (use of chemical softeners) and mechanical (physical) methods.

Chemical Method of Removing Water Hardness utilizes water Softeners. These are of two types: those which lead to precipitation; and those which do not precipitate. Calculated amount of slaked lime or calcium hydroxide is added to the water to remove dissolved calcium, magnesium or iron(II) salt by forming precipitate or undissolved solids. The precipitate is then removed by filtration. It will remove only temporary hardness from water.

Reaction involved:

C a (O H)_{2} (s) + C a (H C O 3)_{2} (a q) \to 2 C a C O_{3} (s) + 2 H_{2} O

$Ca(OH)_2(s) + Ca(HCO3)_2(aq) \rightarrow 2CaCO_3(s) + 2H_2O$

C a (O H)_{2}

$Ca(OH)_2$ is slightly soluble;

C a (H C O_{3})_{2}

$Ca(HCO_3)_2$ is soluble;

C a C O_{3}

$CaCO_3$ is insoluble. Excess of slaked lime could cause hardness, hence the amount added is measured.

Therefore option A is correct

Which letter corresponds to the activation energy of the reaction after the addition of a catalyst?

0%
A
0%
B
0%
C
0%
D
0%
E

Which of the following is regarded as a solid sol?

0%
Pigmented plastics
0%
Coloured glasses
0%
Both A and B
0%
None of the above

Hydrogen in palladium is an example of:

0%
gas in gas
0%
gas in liquid
0%
liquid in solid
0%
gas in solid

Soap lather is an example of :

0%
foam
0%
sol
0%
emulsion
0%
gel

Milk is an example for:

0%
inelastic gel
0%
foam
0%
elastic gel
0%
emulsion

Explanation

An emulsion is a colloid of two or more immiscible liquids where one liquid contains a dispersion of the other liquids. In other words, an emulsion is a special type of mixture made by combining two liquids that normally don't mix. The word emulsion comes from the Latin word meaning "to milk" (milk is one example of an emulsion of fat and water). The process of turning a liquid mixture into an emulsion is called emulsification.

Hence, the correct option is

D

$D$

Detergents are less or non bio-degradable when compare with soaps. For detergents to be bio-degradable in nature, the non-polar part of the molecule should:

0%
consist of a hydrocarbon with more branching
0%
consist of a hydrocarbon with more number of branches and unsaturation
0%
have straight or open chain hydrocarbons
0%
be replaced by aromatic rings substituted by alkyl groups

Which of the following is a property of physisorption?

0%
High specificity
0%
Irreversibility
0%
Non-specificity
0%
None of these.

Which one of the following can form micelle?

0%
$NaCoo----R----CooNa$
0%
R
0%
$NaCOO-R-COONa$
0%
R-R-R

Explanation

Micelles are lipid molecules that arrange themselves in a spherical form in aqueous solutions. They contain both hydrophilic regions (polar head groups) as well as hydrophobic regions (the long hydrophobic chain). Hence it is represented as,

N a^{+} C O O - - - - R - - - -^{-} O O C N a^{+}

$Na^+COO----R----^-OOCNa^+$

An example of colloidal sol in which the affinity of the sol particles for the medium is due to hydrogen bonding is :

0%
Sulphur in water
0%
Gold in water
0%
$Fe(OH)_3$ in water
0%
Protein water

From the following which is not an emulsifer?

0%
Agar
0%
Milk
0%
Gum
0%
Soap

In an experiment,

200 m l

$200ml$ . of

0.5

$0.5$ oxalic acid is shaken with

10 g

$10g$ of activated charcoal and fiftered. The concentration of the filtrate is reduced to

0.4 M

$0.4 M$ . The amount of adsorption

(x / m)

$(x/m)$ is?

0%
$0.9$
0%
$1.8$
0%
$0.18$
0%
$8.09$

F e (O H)_{3}

$Fe(OH)_3$ sol is :

0%
Macro molecular colloid
0%
Multi molecular colloid
0%
Micelles
0%
Negative colloid

Explanation

When a large number of atoms of a substance combine in a dispersion medium having size in the colloidal, the filmed solutions are called multimolecular colloids.

Sulphur solution consists of particles containing about a thousands of

S 8

$S8$ molecules.

F e (O H)_{3}

$Fe(OH)_3$ is a multimolecular colloids.

The process of adsorption of hydrogen over palladium surface is called:

0%
sorption
0%
occlusion
0%
desorption
0%
None of these

Explanation

Adsorption of gas on the surface of solid is also known as occlusion. hence

B

$B$ is correct.

0%
Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
0%
Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
0%
Assertion is correct but Reason is incorrect.
0%
Both Assertion and Reason are incorrect.

Explanation

A positive catalyst increases the rate of a reaction by decreasing the activation energy of a reaction.

Hence option

C

$C$ is correct.

Assertion:

A catalyst enhances the rate of a reaction.

Reason:

The energy of activation of the reaction is lowered in the presence of a catalyst.

0%
Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
0%
Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
0%
Assertion is correct but Reason is incorrect.
0%
Both Assertion is incorrect but Reason is correct.

The role of metal written on arrows in the given chemical reactions is :

0%
catalyst
0%
oxidising agent
0%
reducing agent
0%
dehydrating agent

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

0%
dialysis
0%
peptization
0%
electrophoresis
0%
electrosmosis

Rate of physisorption increases with:

0%
decrease in temperature
0%
increase in temperature
0%
decrease in pressure
0%
decrease in surface area

Dispersed Phase	Dispersion Medium	Name	Example
Solid	Solid	Solid sol	Coloured glass, gems, alloys
Solid	Liquid	sol	Paints, inks, white of eggs mud
Solid	Gas	Aerosol	Smoke, dust
Liquid	Solid	Gel	Curds, pudding, cheese, jellies
Liquid	Liquid	Emulsion	Milk, Cream, Better, Oil in water
Liquid	Gas	Liquid Aerosol	Clouds, Mist, fog (water in air)

CBSE Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 3 - 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 3 - MCQExams.com

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Practice Class 12 Engineering Chemistry Quiz Questions and Answers

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