Surface Chemistry Questions — NEET Chemistry

Q1

Which of the following is a positively charged sol?

A Methylene blue sol

B Congo red sol

C Silver sol

D Sb

_2

S

_3

sol

Correct Answer

Option A

Solution

Methylene blue solution

Q2

Which one is an example of heterogenous catalysis?

A Hydrolysis of sugar catalysed by

\mathrm{H}^{+}

ions.

B Decomposition of ozone is presence of nitrogen monoxide.

C Combination between dinitrogen and dihydrogen to form ammonia in the presence of finely divided iron.

D Oxidation of sulphur dioxide into sulphur trioxide in the presence of oxides of nitrogen.

Correct Answer

Option C

Solution

(1)

\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11 \text{ (aq) }}+\mathrm{H}_{2} \mathrm{O} \stackrel{\mathrm{H}^{+}}{\longrightarrow} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6(\text{ aq) }}+\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6(\text{ aq )}}

(Homogeneous reaction) (2)

2 \mathrm{O}_{3(\mathrm{g})} \stackrel{\mathrm{NO}(\mathrm{g})}{\longrightarrow} 3 \mathrm{O}_{2(\mathrm{g})}

(Homogeneous reaction) (3)

\mathrm{N}_{2(g)}+3 \mathrm{H}_{2(\mathrm{g})} \stackrel{\mathrm{Fe}(\mathrm{s})}{\longrightarrow} 2 \mathrm{NH}_{3(\mathrm{g)}}

(Reactants and catalyst are in different phase) It is heterogeneous reaction (4)

\mathrm{SO}_{2(\operatorname{g)}}+\frac{1}{2} \mathrm{O}_{2(\mathrm{g})} \stackrel{\mathrm{NO}_{(g)}}{\longrightarrow} \mathrm{SO}_{3(\mathrm{g})}

Q3

Pumice stone is an example of -

A gel

B solid sol

C foam

D sol

Correct Answer

Option B

Solution

Pumice stone is an example of solid state

Q4

Shown below are adsorption isotherms for a gas 'X' at temperatures T 1 , T 2 and T 3 : p and

{x \over m}

represent pressure and extent of adsorption, respectively. The correct order of temperatures for the given adsorption is :

A

{T_1} = {T_2} > {T_3}

B

{T_1} > {T_2} > {T_3}

C

{T_3} > {T_2} > {T_1}

D

{T_1} = {T_2} = {T_3}

Correct Answer

Option C

Solution

With increase in temperature, extent of adsorption

\left( {i.e.\,{x \over m}} \right)

decreases so correct order of temperatures will be

{T_3} > {T_2} > {T_1}

Q5

The right option for the statement Tyndall effect is exhibited by, is :

A Urea solution

B NaCl solution

C Glucose solution

D Starch solution

Correct Answer

Option D

Solution

$\bullet$ Tyndall effect is exhibited by colloidal solution only.

$\bullet$ Among the given options, Urea, NaCl and Glucose solutions are true solutions, so cannot show Tyndall effect.

$\bullet$ Starch solution is a colloidal solution therefore can show Tyndall effect.

Q6

Measuring Zeta potential is useful in determining which property of colloidal solution?

A Solubility

B Stability of the colloidal particles

C Size of the colloidal particles

D Viscosity

Correct Answer

Option B

Solution

In colloidal solution, the potential difference between the fixed layer and the diffused layer of opposite charge is known as Zeta potential.

The presence of equal and similar charges on colloidal particles are largely responsible in providing stability to the colloidal solution.

Zeta potential $\propto$ Stability of colloidal particle

Q7

On which of the following properties does the coagulating power of an ion depend?

A The magnitude of the charge on the ion alone

B Size of the ion alone

C Both magnitude and sign of the charge on the ion

D The sign of charge on the ion alone

Correct Answer

Option C

Solution

According to Hardy Schulze rule : 1.

Coagulation of colloidal solution by using an electrolyte depends on the charge present (positive or negative) on colloidal particles as well as on its size.

2.

Coagulating power of an electrolyte depends on the magnitude of charge present on effective ion of electrolyte.

Q8

Which one of the following statements is not correct?

A The value of equilibrium constant is changed in the presence of a catalyst in the reaction at equilibrium.

B Enzymes catalyse mainly bio-chemical reactions.

C Coenzymes increase the catalytic activity of enzyme.

D Catalyst does not initiate any reaction.

Correct Answer

Option A

Solution

A catalyst accelerates the forward and backward reaction to the same extent thus, the equilibrium constant does not change.

Catalyst only speed up the reactions to attain equilibrium faster and does not alter equilibrium constant.

Equilibrium constant varies only when temperature condition of reaction gets changed.

Q9

Fog is a colloidal solution of

A solid in gas

B gas in gas

C liquid in gas

D gas in liquid.

Correct Answer

Option C

Solution

Fog is a colloidal system having dispersed phase as liquid and dispersion medium as gas.

Q10

Which one of the following characteristics is associated with adsorption?

A

\Delta

G and

\Delta

H are negative but

\Delta

S is positive.

B

\Delta

G and

\Delta

S are negative but

\Delta

H is positive.

C

\Delta

G is negative but

\Delta

H and

\Delta

S are positive.

D

\Delta

G,

\Delta

H and

\Delta

S all are negative.

Correct Answer

Option D

Solution

Adsorption is spontaneous process, therefore change in the free energy (

\Delta

G) for the process is negative. As we know that

\Delta

G =

\Delta

H – T

\Delta

S S is negative because adhering of gas molecules to the surface lowers the randomness. $\therefore$

\Delta

G can be –ve only when

\Delta

H is –ve.