Surface Chemistry Test

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Surface Chemistry Test - 21

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Weekly Quiz Competition

Question 1
1 / -0

The oxidation of oxalic acid by acidified $$KMnO_4$$ is an example of autocatalysis. It is due to which of the following?

A
$$SO_4^{2-}$$

B
$$MnO_4^{2-}$$

C
$$Mn^{2+}$$

D
$$K^{\oplus}$$

Solution

In the permanganate titration of oxalic acid in the presence of bench $$H_2SO_4$$ (acid medium), it is found that there is slow discharge of the colour of permanganate solution in the beginning but after sometime, the discharge of the colour becomes faster. This is due to the formation of $$MnSO_4$$ during the reaction which acts as a catalyst for the same reaction. Thus, $$Mn^{+2}$$ is an "auto catalyst" for this reaction. This is an example of auto catalyst.
Question 2
1 / -0

The substance on whose surface adsorption takes place is called an _______ .

A
absorbent

B
absorbate

C
solute

D
solvent

Solution

The substance on whose surface adsorption takes place is called an absorbent.
In other words, a substance which adsorbs another substance (adsorbate) on its surface is called an adsorbent.
For example, when hydrogen gas is adsorbed on the surface of Pt metal, hydrogen is called adsorbate and Pt is called adsorbent.
Question 3
1 / -0

Milk is an example of water in oil emulsions.

A
True

B
False

C
Ambiguous

D
Data insufficient

Solution

Oil in water (o/w) type: In these emulsions, oil forms the dispersed phase and water, the dispersion medium. For example, milk, vanishing cream, etc. These are also called aqueous emulsions.
Water in oil (w/o) type: In these emulsions, water is in the dispersed phase and oil in the dispersion medium. For example, butter, cold cream etc. are also called oil emulsions.
Question 4
1 / -0

An emulsifier is a substance :

A
which stabilises an emulsion

B
which breaks the emulsion into its constituent liquids

C
which can convert liquid into an emulsion

D
which bring about coagulation of an emulsion
Solution
Explanation:
- An emulsifier is a substance that acts as a stabilizer in an emulsion and prevents the mixing of two solutions.
- An emulsifier has a water-loving hydrophilic head and an oil-loving hydrophobic tail.
- The hydrophilic head is for the aqueous phase and the hydrophobic tail is for the oil phase.
e.g. lecithin.

Hence, the correct answer is option $$A$$.

Question 5

1 / -0

Small liquid droplets dispersed in another liquid is called:

suspension

emulsion

gel

true solution

Solution

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)

Question 6
1 / -0

The heat of physisorption lie in the range of :

A
$$1$$ to $$10$$ $$kJ\:mol^{-1}$$

B
$$20$$ to $$40$$ $$kJ\:mol^{-1}$$

C
$$40$$ to $$200$$ $$kJ\:mol^{-1}$$

D
$$200$$ to $$400$$ $$kJ\:mol^{-1}$$

Solution

The heat of physisorption lie in the range of 20 to 40 $$\displaystyle kJ/mol$$. The value is small as weak van der waals forces are involved. It has negative sign as the adsorption is an exothermic reaction.
Question 7
1 / -0

Smoke precipitator works on the principle of :

A
distribution law

B
neutralization of charge on colloids

C
Le-Chaterlier's principle

D
addition of electrolytes

Solution

Smoke precipitator works on the principle of neutralization of charge on colloids.

Smoke coming out of the chimneys contain a lot of unburnt carbon particle.

Smoke is the colloidal solution of the solid particles such as carbon, arsenic, dust particles etc. These particles are injurious to health and have to be precipitated.

Carbon particle is charged particles and can not be precipitated. Thus, a metal plate of an oppositely charged particle is used for their precipitation.

This is done by the Cottrell smoke precipitator which neutralizes the charge on the carbon particles and neutralizes them.

In this way, smoke coming out of the chimneys gets free from the charged particles.
Question 8
1 / -0

The colloidal dispersion of a liquid in a liquid is called:

A
mixture

B
emulsion

C
precipite

D
none of these

Solution

The colloidal dispersion of a liquid in a liquid is called emulsion.
In these systems, one liquid is dispersed in another liquid immiscible with it.
For example, milk is an emulsion of oil in water. The particles of liquid fat are dispersed in water.
Codliver oil is an emulsion of water in oil. consists of particles of water dispersed in oil.
Question 9
1 / -0

The ______ colloidal dispersions are called emulsions.

A
liquid-liquid

B
solid-solid

C
gas-gas

D
A and C

Solution

The liquid-liquid colloidal dispersions are called emulsions.
In these systems, one liquid is dispersed in another liquid immiscible with it. For example, milk is an emulsion of oil in water. The particles of liquid fat are dispersed in water. Cod liver oil is an emulsion of water in oil. It consists of particles of water dispersed in oil.
Question 10
1 / -0

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

A
mixture

B
adsorption

C
reduction

D
none of these

Solution

The adhering of the molecules of gas on the surface of a solid is called adsorption. It is a surface phenomenon. It is defined as the phenomenon of accumulation of higher concentration of one substance on the surface of another than in the bulk.

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Surface Chemistry Test - 21

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Surface Chemistry Test - 21

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Question 1

$$SO_4^{2-}$$

$$MnO_4^{2-}$$

$$Mn^{2+}$$

$$K^{\oplus}$$

Solution

Question 2

absorbent

absorbate

solute

solvent

Solution

Question 3

True

False

Ambiguous

Data insufficient

Solution

Question 4

which stabilises an emulsion

which breaks the emulsion into its constituent liquids

which can convert liquid into an emulsion

which bring about coagulation of an emulsion

Solution

Question 5

suspension

emulsion

gel

true solution

Solution

Question 6

$$1$$ to $$10$$ $$kJ\:mol^{-1}$$

$$20$$ to $$40$$ $$kJ\:mol^{-1}$$

$$40$$ to $$200$$ $$kJ\:mol^{-1}$$

$$200$$ to $$400$$ $$kJ\:mol^{-1}$$

Solution

Question 7

distribution law

neutralization of charge on colloids

Le-Chaterlier's principle

addition of electrolytes

Solution

Question 8

mixture

emulsion

precipite

none of these

Solution

Question 9

liquid-liquid

solid-solid

gas-gas

A and C

Solution

Question 10

mixture

adsorption

reduction

none of these

Solution

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