Surface Chemistry Test

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Surface Chemistry Test - 58

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Weekly Quiz Competition

Question 1
1 / -0

List I contains the type of colloid while List ll contains the examples.
List I List II
A. Sol p. Dust
B. Aerosol q. Cheese
C. Gel r. Soap lather
D. Foam s. Plant cell fluid

A
A-s B-r C-p D-q

B
A-s B-p C-q D-r

C
A-r B-s C-q D-p

D
A-r B-p C-s D-q

E
A-p B-r C-s D-q

Solution

(a) Plant cell fluid is a sol.
(b) Dust particles form aerosol.
(a) Cheese is gel.
(d) Soap lather is foam.
So, correct matching is:
(A)-(s), (B)-(p), (C)-(q), (D)-(r)
Question 2
1 / -0

Gold sol can be prepared by:

A
hydrolysis of gold(III) chloride

B
oxidation of gold by aqua-regia

C
peptization

D
treating gold (III) chloride with metallic zinc

E
reduction of gold (III) chloride with formalin solution

Solution

Gold sol can be prepared by reducing gold (III) chloride with formalin solution (aqueous solution of formaldehyde)

$$2AuCl_{3} + \underset {Formalin\ solution}{\underbrace {3HCHO + 3H_{2}O}} \xrightarrow {Reduction} \underset {sol}{2\ Au} + 3HCOOH + 6HCl$$.
Question 3
1 / -0

Which type of catalyst is ethanol in the following reaction?

$$CHCl_3+O_2\xrightarrow{{C_2H_5OH}}2COCl_2+2HCl$$.

A
Positive catalyst

B
Negative catalyst

C
Bio-catalyst

D
Autocatalyst

Solution

Chloroform on oxidation produces phosgene gas which is a toxic gas, so as to deaccelerate the reaction we will drop ethanol solution so that this reaction does not occur. So, $$C_2H_5OH$$ is a negative catalyst.
Hence option B is correct.
Question 4
1 / -0

The enthalpy($$H$$) of an elementary exothermic reaction $$A\rightleftharpoons B$$ is schematically plotted against the reaction coordinate. The plots in the presence and absence of a catalyst are shown in dashed and solid lines, respectively. Identify the correct plot for the reaction.

A

B

C

D

Solution

A catalyst provides an alternate pathway for a reaction to occur. The alternate pathway has a lower activation energy $$(E_a)$$, meaning that the reactant molecules do not need to collide with as much energy in order for a reaction to occur. So more collision results in a reaction, so the reaction rate is faster.

Note that adding a catalyst does not change the amount of energy released ($$\triangle H)$$ for the reaction.
Question 5
1 / -0

Which one of the following processes does not involve coagulation?

A
Peptization

B
Formation of delta

C
Purification of drinking water using alum

D
Tanning of leather using tannin

Solution

Peptization does not involve coagulation.
Peptization is the process of converting a precipitate into colloidal particles by adding suitable electrolyte.
Coagulation represents change of colloidal state to suspension state.
Thus, coagulation and peptization represents opposite processes.
Question 6
1 / -0

Match list I with List II and select the correct answer using the codes given below the lists:
List I List II
(A) Coagulation (1) Scattering
(B) Lyophilization (2) Washing of precipitates
(C) Peptization (3) Purification of colloids
(D) Tyndall (4) Electrolyte

A
A-4; B-3; C-2; D-1

B
A-2; B-1; C-3; D-4

C
A-3; B-4; C-2; D-1

D
A-4; B-3; C-1; D-1

Solution

Coagulation is achieved by the addition of an electrolyte. The colloidal particles adsorb the ions of opposite charge to that present on the surface of the particle. The charge on colloidal particles is neutralized and the repulsion between particles reduces.

Lyophilization is a method of purification of colloids. Other methods include dialysis, ultrafiltration, and ultracentrifugation.

Peptization is the washing of precipitates. It converts a precipitate into colloidal particles by adding a suitable electrolyte.

The Tyndall effect refers to light scattering by colloidal particles. This makes the path of light visible through dispersion.
Question 7
1 / -0

Select the correct statement.

A
If the critical micelle concentration (CMC) of a soap is $$10^{-3}$$mol/L the $$10^{-4}$$M solution of soap is a colloidal solution.

B
Charge of dispersed phase and dispersion medium in a colloidal solution can be identified by electrodialysis process.

C
Peptization is defined as the process of converting colloidal sol into precipitate by shaking it with dispersion medium in the small amount of electrolyte

D
The emulsion is water in oil (W/O) when some oil soluble dye is added to it and background becomes coloured.

Solution

An emulsion is a colloidal solution in which both dispersion medium as well as dispersed phase are liquid
In dye test when some oil soluble dye is added and it background gets colored then the emulsion is water-in-oil type.
Question 8
1 / -0

Some medicines are more effective in the colloidal form because of:

A
the charged colloidal particles present in it

B
the large surface area and easy assimilation

C
precipitation of medicine in the blood

D
the stabilisation of medicine in colloidal form
Solution
- A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called dispersion medium.
- Colloidal medicines are more effective because they have large surface area and are therefore easily assimilated.
Various applications of collids are-
- Purification of drinking water
- Cleansing action of soaps and detergents as Medicines
- Photographic plates and films
Question 9
1 / -0

When an excess of a very dilute aqueous solution of KI is added to a very dilute aqueous solution of silver nitrate, the colloidal particles of silver iodide are associated with which of the following Helmholtz double layer?

A

B

C

D

Solution

The Helmholtz double layer contains a layer of opposite charges on the sulfur of colloidal particles.
$$AgNO_3+KI(excess)\rightarrow AgI+KNO_3$$
$$AgI+KI\rightarrow AgI/I^-:K^+$$
Question 10
1 / -0

An inhibitor is essentially:

A
a negative catalyst

B
autocatalyst

C
heterogeneous

D
homogeneous catalyst

Solution

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Re-Attempt Weekly Quiz Competition

List I	List II
A. Sol	p. Dust
B. Aerosol	q. Cheese
C. Gel	r. Soap lather
D. Foam	s. Plant cell fluid

List I	List II
(A) Coagulation	(1) Scattering
(B) Lyophilization	(2) Washing of precipitates
(C) Peptization	(3) Purification of colloids
(D) Tyndall	(4) Electrolyte

Surface Chemistry Test - 58

Result

Surface Chemistry Test - 58

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Question 1

A-s B-r C-p D-q

A-s B-p C-q D-r

A-r B-s C-q D-p

A-r B-p C-s D-q

A-p B-r C-s D-q

Solution

Question 2

hydrolysis of gold(III) chloride

oxidation of gold by aqua-regia

peptization

treating gold (III) chloride with metallic zinc

reduction of gold (III) chloride with formalin solution

Solution

Question 3

Positive catalyst

Negative catalyst

Bio-catalyst

Autocatalyst

Solution

Question 4

Solution

Question 5

Peptization

Formation of delta

Purification of drinking water using alum

Tanning of leather using tannin

Solution

Question 6

A-4; B-3; C-2; D-1

A-2; B-1; C-3; D-4

A-3; B-4; C-2; D-1

A-4; B-3; C-1; D-1

Solution

Question 7

If the critical micelle concentration (CMC) of a soap is $$10^{-3}$$mol/L the $$10^{-4}$$M solution of soap is a colloidal solution.

Charge of dispersed phase and dispersion medium in a colloidal solution can be identified by electrodialysis process.

Peptization is defined as the process of converting colloidal sol into precipitate by shaking it with dispersion medium in the small amount of electrolyte

The emulsion is water in oil (W/O) when some oil soluble dye is added to it and background becomes coloured.

Solution

Question 8

the charged colloidal particles present in it

the large surface area and easy assimilation

precipitation of medicine in the blood

the stabilisation of medicine in colloidal form

Solution

Question 9

Solution

Question 10

a negative catalyst

autocatalyst

heterogeneous

homogeneous catalyst

Solution

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