Surface Chemistry Test

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Surface Chemistry Test - 56

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Weekly Quiz Competition

Question 1
1 / -0

A colloidal system having a solid substance as a dispersed phase and a liquid as a dispersion medium is classified as:

A
solid sol

B
gel

C
emulsion

D
sol
Solution
Correct Option: D

Explanation
- Colloids consist of two phases:
  1. Dispersed phase: Component present in small quantity.
  2. Dispersion medium: Component present in excess.
- The particles of the dispersed phase are scattered in the dispersion medium
- When solid particles are dispersed in solid, it is known as $$Solid$$ $$sol$$. Examples include Ruby glass, etc.
- When liquid particles are dispersed in a solid, it is known as $$Gel$$. Examples include cheese, butter, etc.
- When liquid particles are dispersed in a liquid, it is known as $$Emulsion$$. Examples include milk, hair cream, etc.
- When solid particles are dispersed in a liquid, it is called $$Sol$$. Examples include Gold sol, ink, paint, etc.
Hence, a colloidal system having solid as dispersed phase and liquid as dispersion medium is called a sol.
Question 2
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The name aquadag is given to the colloidal solution of:

A
copper in water

B
platinum in water

C
gold in water

D
graphite in water

Solution

Aquadag is a the name of a water-based colloidal graphite coating which is a colloidal solution of graphite in water.
Question 3
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Which of the following reactions is not used for the preparation of a colloidal solution?

A
$$2Au{ Cl }_{ 3 }+3Sn{ Cl }_{ 2 }\longrightarrow 3Sn{ Cl }_{ 4 }+2Au$$

B
$$Fe{ Cl }_{ 3 }+3{ H }_{ 2 }O\longrightarrow Fe{ \left( OH \right) }_{ 3 }+3HCl$$

C
$$2Mg+{ CO }_{ 2 }\longrightarrow 2MgO+C$$

D
$$2{ H }_{ 2 }S+2S{ O }_{ 2 }\longrightarrow 2{ H }_{ 2 }O+3S$$

Solution

$$2Mg+CO_2\rightarrow 2MgO+C$$ does not produce any colloidal solution, whereas the other three reactions produce Gold sol, ferric hydroxide sol and sulphur sol.
Question 4
1 / -0

The heats of adsorption (in $$kJ/mol$$) in physisorption or physical adsorption lie in the range of:

A
$$40 - 400$$

B
$$40 - 100$$

C
$$10 - 40$$

D
$$200 - 400$$

Solution

The heats of adsorption in physisorption or physical adsorption lies in the range of $$10−40\ kJ/mol$$. It is less as compared to chemisorption as there is no chemical reaction involved in it.
Question 5
1 / -0

Peptization denotes:

A
digestion of food

B
hydrolysis of proteins

C
breaking of dispersion into colloidal state

D
precipitation of a solid from colloidal state

Solution

The dispersion of a freshly precipitated material into colloidal solution by the action of an electrolyte in solution is termed as peptization which involves breaking of suspension into colloidal state by adsorption of suitable ions and electrically charged particles then split from the precipitate as colloidal particles.
Question 6
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Which one of the following is not a correct statement?

A
Physical adsorption is reversible in nature.

B
Physical adsorption involves Van der Waals forces.

C
Rate of chemical adsorption increases with increase of temperature.

D
High activation energy is involved in chemical adsorption.

Solution

Chemisorption involves high activation energy. So, first, it increases and then decreases with increase in temperature. The initial increase is due to the heat supplied which act as activation energy required for chemisorption. But later it decreases due to the exothermic nature of adsorption at equilibrium.

Thus statement given in option C is incorrect.
Question 7
1 / -0

To stop bleeding from an injury ferric chloride can be applied
Which comment about the statement is justified?

A
It is not true, ferric chloride is a poison

B
It is true, $${Fe}^{3+}$$ ions coagulate blood which is negatively charged sol

C
It is not true, $${Cl}^{-}$$ ions from positively charged sol, profuse bleeding takes place

D
It is true, coagulation takes place because of formation of negatively charged sol with $${Cl}^{-}$$ ions.

E
It is not true, ferric chloride is ionic and gets into blood stream

Solution

To stop bleeding from an injury, Ferric chloride can be applied because of the following reason:
(A) $$Fe^{3+}$$ ions coagulate blood which is a negatively charged solution
(B) $$Cl^−$$ ions coagulate blood which is a positively charged solution
Blood being a colloidal solution, its coagulation by Hardy-Shuze's law states " Higher the charge on cation higher will be its efficiency to coagulate the colloidal solution" . Thus Option B is correct.
Question 8
1 / -0

Peptization of $$Sn{ O }_{ 2 }$$ by $$NaOH$$ gives:

A
$$\left[ Sn{ O }_{ 2 } \right] Sn{ O }_{ 3 }^{ 2- }:2{ Na }^{ + }$$

B
$$ \left[ Sn{ O }_{ 2 } \right] { Sn }^{ 4+ }:{ O }_{ }^{ 2- }$$

C
$$\left[ Sn{ O }_{ 2 } \right] Na:{ OH }^{ - }$$

D
$$\left[ Sn{ O }_{ 2 } \right] { Sn }^{ 4+ }:{ OH }^{ - }$$

Solution

The dispersion of a freshly precipitated material into colloidal solution by the action of an electrolyte in solution is termed peptization. The electrolyte used is called a peptizing agent. e.g. Freshly prepared stannic oxide on treatment with a small amount of dilute hydrochloric acid forms a stable colloidal solution of stannic oxide. i.e. $$[SnO_2]SnO_3^{2-}:\ 2Na^+$$
Question 9
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Directions For Questions

Emulsions are also the colloidal solutions in which disperse phase, as well as a dispersion medium, are liquids. It may be oil in water or water in oil type. Bancroft proposed that the phase in which the emulsion. Emulsifiers can be used to stabilize the emulsions. The emulsifier is more soluble becomes the outer phase of the emulsion. Emulsifiers can be used to stabilize the emulsion. Soaps, detergents, proteins, and gum etc., are used as emulsifiers.

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Which of the following is homogeneous?

A
Milk

B
Paint

C
Shampoo

D
None of these

Solution

Heterogeneous mixtures can be colloids or suspensions. A suspension differs from a colloid because one chemical is suspended, or temporarily mixed in another. Examples of heterogeneous mixtures include smoke, milk, mayonnaise, muddy water and marshmallows.
Paint is considered a colloid, which is a heterogeneous mixture where one chemical is dispersed in another.
Thus Option C is correct.
Question 10
1 / -0

Silver iodide is used for producing artificial rains because $$AgI$$:

A
is easy to spray at high altitude

B
is insoluble in water

C
is easy to synthesize

D
has crystals similar to ice

Solution

Solid silver iodide is preferred as a nucleator for artificially stimulated rain because its crystal lattice parameters are close to those of ice, and for that reason are more effective than other salts in causing small ice crystals in clouds to melt.

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Surface Chemistry Test - 56

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Surface Chemistry Test - 56

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Question 1

solid sol

gel

emulsion

sol

Solution

Question 2

copper in water

platinum in water

gold in water

graphite in water

Solution

Question 3

$$2Au{ Cl }_{ 3 }+3Sn{ Cl }_{ 2 }\longrightarrow 3Sn{ Cl }_{ 4 }+2Au$$

$$Fe{ Cl }_{ 3 }+3{ H }_{ 2 }O\longrightarrow Fe{ \left( OH \right) }_{ 3 }+3HCl$$

$$2Mg+{ CO }_{ 2 }\longrightarrow 2MgO+C$$

$$2{ H }_{ 2 }S+2S{ O }_{ 2 }\longrightarrow 2{ H }_{ 2 }O+3S$$

Solution

Question 4

$$40 - 400$$

$$40 - 100$$

$$10 - 40$$

$$200 - 400$$

Solution

Question 5

digestion of food

hydrolysis of proteins

breaking of dispersion into colloidal state

precipitation of a solid from colloidal state

Solution

Question 6

Physical adsorption is reversible in nature.

Physical adsorption involves Van der Waals forces.

Rate of chemical adsorption increases with increase of temperature.

High activation energy is involved in chemical adsorption.

Solution

Question 7

It is not true, ferric chloride is a poison

It is true, $${Fe}^{3+}$$ ions coagulate blood which is negatively charged sol

It is not true, $${Cl}^{-}$$ ions from positively charged sol, profuse bleeding takes place

It is true, coagulation takes place because of formation of negatively charged sol with $${Cl}^{-}$$ ions.

It is not true, ferric chloride is ionic and gets into blood stream

Solution

Question 8

$$\left[ Sn{ O }_{ 2 } \right] Sn{ O }_{ 3 }^{ 2- }:2{ Na }^{ + }$$

$$ \left[ Sn{ O }_{ 2 } \right] { Sn }^{ 4+ }:{ O }_{ }^{ 2- }$$

$$\left[ Sn{ O }_{ 2 } \right] Na:{ OH }^{ - }$$

$$\left[ Sn{ O }_{ 2 } \right] { Sn }^{ 4+ }:{ OH }^{ - }$$

Solution

Question 9

Milk

Paint

Shampoo

None of these

Solution

Question 10

is easy to spray at high altitude

is insoluble in water

is easy to synthesize

has crystals similar to ice

Solution

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