Surface Chemistry

NEET Chemistry · 98 questions · Page 3 of 10 · Click an option or "Show Solution" to reveal answer

Q21

According to the adsorption theory of catalysis, the speed of the reaction increases because

A the concentration of reactant molecules at the active centres of the catalyst becomes high due to adsorption

B in the process of adsorption , the activation energy of the molecules becomes large

C adsorption produces heat which increases the speed of the reaction

D adsorption lowers the activation energy of the reaction.

Correct Answer

Option D

Solution

The speed of the reaction increases because adsorption lowers the activation energy of the reaction.

Q22

Position of non polar and polar part in micelle

A polar at outer surface but non polar at inner surface

B polar at inner surface non polar at outer surface

C distributed over all the surface

D are present in the surface only.

Correct Answer

Option A

Solution

Micelles are formed by the association of colloids.

They are formed by lyophilic and lyophobic groups.

As the concentration increases the lyophobic parts receding away from the solvent approach each other are forms a cluster, the lyophobic ends are in the interior, lyophilic groups projecting outwards in contact with the solvent.

Q23

Which is not correct regarding the adsorption of a gas on surface of a solid?

A On increasing temperature adsorption increases continuously.

B Enthalpy and entropy change is negative.

C Adsorption is more for some specific substance.

D It is a reversible reaction.

Correct Answer

Option A

Solution

Adsorption is the property of a substance to hold or to concentrate liquid or dissolved substances upon its surface.

Solids adsorb greater amount of substance at lower temperature and in general adsorption decreases with increasing temperature.

Q24

Which one of the following method is commonly used method for destruction of colloid?

A Dialysis

B Condensation

C Filteration by animal membrane

D By adding electrolyte

Correct Answer

Option D

Solution

By adding electrolytes the colloidal particles are precipitated.

The electrolytes neutralise the charge of colloids leading to their coagulation and thus destroy the colloid.

Q25

Which mixture of the solution will lead to the formation of negatively charged colloidal [AgI] I – sol. ?

A 50 mL of 2 M AgNO 3 + 50 mL of 1.5 M KI

B 50 mL of 0.1 M AgNO 3 + 50 mL of 0.1 M KI

C 50 mL of 1 M AgNO 3 + 50 mL of 1.5 M KI

D 50 mL of 1 M AgNO 3 + 50 mL of 2 M KI

Correct Answer

Option C

Solution

AgNO 3 + KI $\to$ AgI + KNO 3 If KI is in excess then negatively charged colloid, [AgI]I – is formed.

Whereas, if AgNO 3 is in excess positively charged colloid AgI/Ag + will form.

Q26

The formation of gas at the surface of tungsten due to adsorption is the reaction of order :

A 0

B 1

C 2

D insufficient data

Correct Answer

Option A

Solution

It is zero order reaction [NOTE : Adsorption of gas on metal surface is of zero order]

Q27

An example of solid sol is :

A Butter

B Hair cream

C Gem stones

D Paint

Correct Answer

Option C

Solution

An example of solid sol is gem stones.

Q28

A colloidal system consisting of a gas dispersed in a solid is called a/an :

A foam

B aerosol

C solid sol

D gel

Correct Answer

Option C

Solution

A colloidal system consisting of a gas dispersed in a solid is called a ‘solid sol’.

Q29

Which of the following is a correct statement?

A Brownian motion destabilises sols.

B Any amount of dispersed phase can added to emulsion without destablising it.

C Mixing two oppositely charged sols in equal amount neutralises charges and stabilises colloids.

D Presence of equal and similar charges on colloidal particles provides stability to the colloidal solution.

Correct Answer

Option D

Solution

As equal & similar charge particle will repel each other, hence will never precipitate.

Q30

Which of the following salt solutions would coagulate the colloid solution formed when

\mathrm{FeCl_3}

is added to

\mathrm{NaOH}

solution, at the fastest rate?

A 10 mL of 0.15 mol dm

^{-3}

CaCl

_2

B 10 mL of 0.2 mol dm

^{-3}

AlCl

_3

C 10 mL of 0.1 mol dm

^{-3}

_2

_4

D 10 mL of 0.1 mol dm

^{-3}

_3

(PO

_4

)

_2

Correct Answer

Option B

Solution

In the coagulation of a negative sol, the flocculating power is in the order. $\therefore \mathrm{Al}^{3+}>\mathrm{Ba}^{2+}>\mathrm{Na}^{+}$ and $\mathrm{FeCl}_{3}$ with $\mathrm{NaOH}$ forms a negative sol. $\therefore \mathrm{AlCl}_{3}$ coagulate it most.

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