Surface Chemistry Test

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Surface Chemistry Test - 38

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Weekly Quiz Competition

Question 1
1 / -0

A colloidal system in which liquid is a dispersed phase and solid is dispersion medium is classified as:

A
gel

B
sol

C
emulsion

D
aerosol
Solution
- A colloidal system in which liquid is a dispersed phase and solid is dispersion medium is known as Gel. Example-Cheese, jellies.
Question 2
1 / -0

Traces of molybdenum are used with finely divided iron which acts as a catalyst during Haber's process for the synthesis of ammonia. Here molybdenum:

A
acts as a promoter to increase the activity of the catalyst

B
acts as a poison to decrease the activity of the catalyst

C
provides a new pathway to the reaction

D
forms another intermediate compound with lesser activation energy
Solution
- Substances, which accelerate the rate of a chemical reaction and themselves remain chemically and quantitatively unchanged after the reaction, are known as catalysts.
- Promoters are substances that enhance the activity of a catalyst while poisons decrease the activity of a catalyst.
- In Haber’s process for manufacture of ammonia, molybdenum acts as a promoter for iron which is used as a catalyst.
$$N_2(g)+3H_2(g)\rightarrow 2NH_3(g)$$
Question 3
1 / -0

Which is correct in case of Van der Waals adsorption?

A
High temperature, low pressure

B
High temperature, high pressure

C
Low temperature, low pressure

D
Low temperature, high pressure
Solution
- If the accumulation of gas on the surface of a solid occurs on account of weak van der Waals’ forces, the adsorption is termed as physical adsorption or physisorption.
Hence, Physisorption can also be called as Van der Waals adsorption.
- Physical adsorption of a gas by a solid is generally reversible. We can say by Le-Chatelier's principle that more of gas is adsorbed when pressure is increased as the volume of the gas decreases and since the adsorption process is exothermic, the physical adsorption occurs readily at low temperature and decreases with increasing temperature.
- So the correct case is when it is Low temperature and high pressure the Physisorption tends to happen.
Question 4
1 / -0

Which of the following statements is not correct about physisorption?

A
It is a reversible process.

B
It requires less heat of adsorption.

C
It requires activation energy.

D
It takes place at low temperature.
Solution
If the accumulation of gas on the surface of a solid occurs on account of weak van der Waals’ forces, the adsorption is termed as physical adsorption or physisorption.
Characteristics of Physisorption are-
It is a Reversible process.
It is not specific in nature.
It depends on the nature of gas. More easily liquefiable gases are adsorbed readily.
Enthalpy of adsorption is low.
Low temperature is favourable for adsorption.
There is no necessity of activation energy.
It depends on the surface area.
So, here option C is the wrong statement about Physisorption.
Question 5
1 / -0

The incorrect statement about physical adsorption is that :

A
it lacks specificity

B
it is generally reversible

C
porous surfaces are good adsorbent

D
heat of adsorption is quite high
Solution
If the accumulation of gas on the surface of a solid occurs on account of weak van der Waals’ forces, the adsorption is termed as physical adsorption or physisorption.
Characteristics of Physisorption are-
It is not Specific in nature.
It is a Reversible process.
It is not specific in nature.
It depends on the nature of gas. More easily liquefiable gases are adsorbed readily.
Enthalpy of adsorption is low.
Low temperature is favourable for adsorption.
There is no necessity of activation energy.
It depends on the surface area. Hence, porous surfaces are good adsorbents.
So, here option D is the wrong statement about Physisorption.
Question 6
1 / -0

What is the role of activated charcoal in gas masks used in mines?

A
It acts as an adsorbent for poisonous gases present in coal mines.

B
It acts as an adsorbent for coal particles present in coal mines.

C
It acts as a mask through which exhaled gases are diffused out.

D
It acts as a base for scattering the light.
Solution
- Gas mask generally consists of activated charcoal or mixture of adsorbents is usually used for breathing in coal mines.
- Activated charcoal acts as adsorbent which adsorbs other gases on its surface. In Gas masks, they adsorb poisonous gases and hence prevent various occupational hazards.
Question 7
1 / -0

The term activation of adsorbent is used when:

A
adsorbing power is increased by increasing surface area by making the surface rough

B
adsorbing power is increased by dipping the surface in acid to make it smooth

C
adsorbing power is increased by dissolving it in water

D
adsorbing power is decreased to reduce the extent of adsorption.

Solution

Activation of an adsorbent means, increasing the adsorbing power of the adsorbent. This can be achieved by, making their surface rough by mechanical rubbing or by chemical action. By doing so, it will increase the specific area of the adsorbent.
Question 8
1 / -0

Which of the following is an example of heterogeneous catalysis?

A
$$4NH_{3(g)}$$ + 5$$O_{2(g)}$$ $$\xrightarrow[]{Pt_{(s)}}$$

B
$$2SO_{2}$$ + $$O_{2}$$ $$\xrightarrow[]{NO_{(g)}}2SO_{3}$$

C
$$CH_{3}COOCH_{3(l)}$$ + $$H_{2}O$$ $$\xrightarrow[]{HCl_{(aq)}}$$ $$CH_{3}COOH$$ + $$CH_{3}OH$$

D
$$C_{12}H_{22}O_{11}$$ + $$H_{2}O$$ $$\xrightarrow[]{H_{2}SO_{4}}$$ $$C_{6}H_{12}O_{6}$$ +$$C_{6}H_{12}O_{6}$$

Solution

$$\bf{Hint-}$$ The catalytic process in which the reactants and the catalyst are in different phases is known as heterogeneous catalysis.

$$\bf{Explanation-}$$

As here all the reactants and products are in the gaseous state while the catalyst is $$Pt$$ which is in solid-state.
$$4N_{3(g)}$$ + 5$$O_{2(g)}$$ $$\xrightarrow[]{Pt_{(s)}}$$ 4$$NO_{(g)}$$ + 6$$H_{2}O_{(g)}$$
This is an example of heterogeneous catalysis as the catalyst is present in different phases than that of the reactants.

Following the reaction is the example of a homogeneous catalyst as the catalyst and the reactants are in the same phase.
$$2SO_{2(g)}$$ + $$O_{2(g)}$$ $$\xrightarrow[]{NO_{(g)}}2SO_{3(g)}$$

$$CH_{3}COOCH_{3(l)}$$ + $$H_{2}O_{(l)}$$ $$\xrightarrow[]{HCl_{(aq)}}$$ $$CH_{3}COOH_{(aq)}$$ + $$CH_{3}OH_{(aq)}$$

$$C_{12}H_{22}O_{11(aq)}$$ + $$H_{2}O_{(l)}$$ $$\xrightarrow[]{H_{2}SO_{4}}$$ $$C_{6}H_{12}O_{6(aq)}$$ +$$C_{6}H_{12}O_{6(aq)}$$

$$\bf{Conclusion-}$$ Hence, option A is correct.
Question 9
1 / -0

Which kind of catalysis can be explained on the basis of adsorption theory?

A
Homogeneous catalysis

B
Heterogeneous catalysis

C
Negative catalysis

D
Auto catalysis
Solution
- The reactants in gaseous state or in solutions, are adsorbed on the surface of the solid catalyst. The increase in concentration of the reactants on the surface increases the rate of reaction. Adsorption being an exothermic process, the heat of adsorption is utilised in enhancing the rate of the reaction.
Heterogeneous catalysis involves five steps-
Diffusion of reactants to the surface of the catalyst.
Adsorption of reactant molecules on the surface of the catalyst. (Occurrence of chemical reaction on the catalyst’s surface through formation of an intermediate.
Desorption of reaction products from the catalyst surface, and thereby, making the surface available again for more reaction to occur.
Diffusion of reaction products away from the catalyst’s surface.
Question 10
1 / -0

Which of the following will not form a colloidal system?

A
Solid-gas

B
Liquid-gas

C
Gas-gas

D
Gas-liquid
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.
- The essential difference between a solution and a colloid is that of particle size. While in a solution, the constituent particles are ions or small molecules. In a colloid, the dispersed phase may consist of particles of a single macromolecule (such as protein or a synthetic polymer) or an aggregate of many atoms, ions or molecules.
- Gas-gas colloidal system is not possible as we can't distinguish between the dispersed phase and dispersed medium.

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Surface Chemistry Test - 38

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Surface Chemistry Test - 38

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SHARING IS CARING

Question 1

gel

sol

emulsion

aerosol

Solution

Question 2

acts as a promoter to increase the activity of the catalyst

acts as a poison to decrease the activity of the catalyst

provides a new pathway to the reaction

forms another intermediate compound with lesser activation energy

Solution

Question 3

High temperature, low pressure

High temperature, high pressure

Low temperature, low pressure

Low temperature, high pressure

Solution

Question 4

It is a reversible process.

It requires less heat of adsorption.

It requires activation energy.

It takes place at low temperature.

Solution

Question 5

it lacks specificity

it is generally reversible

porous surfaces are good adsorbent

heat of adsorption is quite high

Solution

Question 6

It acts as an adsorbent for poisonous gases present in coal mines.

It acts as an adsorbent for coal particles present in coal mines.

It acts as a mask through which exhaled gases are diffused out.

It acts as a base for scattering the light.

Solution

Question 7

adsorbing power is increased by increasing surface area by making the surface rough

adsorbing power is increased by dipping the surface in acid to make it smooth

adsorbing power is increased by dissolving it in water

adsorbing power is decreased to reduce the extent of adsorption.

Solution

Question 8

$$4NH_{3(g)}$$ + 5$$O_{2(g)}$$ $$\xrightarrow[]{Pt_{(s)}}$$

$$2SO_{2}$$ + $$O_{2}$$ $$\xrightarrow[]{NO_{(g)}}2SO_{3}$$

$$CH_{3}COOCH_{3(l)}$$ + $$H_{2}O$$ $$\xrightarrow[]{HCl_{(aq)}}$$ $$CH_{3}COOH$$ + $$CH_{3}OH$$

$$C_{12}H_{22}O_{11}$$ + $$H_{2}O$$ $$\xrightarrow[]{H_{2}SO_{4}}$$ $$C_{6}H_{12}O_{6}$$ +$$C_{6}H_{12}O_{6}$$

Solution

Question 9

Homogeneous catalysis

Heterogeneous catalysis

Negative catalysis

Auto catalysis

Solution

Question 10

Solid-gas

Liquid-gas

Gas-gas

Gas-liquid

Solution

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