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Surface Chemistry

NEET Chemistry · 98 questions · Page 5 of 10 · Click an option or "Show Solution" to reveal answer

Q41
Lyophilic sols are more stable than lyophobic sols because :
A there is a strong electrostatic repulsion between the negatively charged colloidal particles.
B the colloidal particles have positive charge.
C the colloidal particles have no charge.
D the colloidal particles are solvated.
Correct Answer
Option D
Solution

In the lyophilic colloids, the colloidal particles are extensively solvated.

Q42
A 42.12% (w/v) solution of NaCl causes precipitation of a certain sol in 10 hours. The coagulating value of NaCl for the sol in 2 hours is : [Given : Molar mass : Na = 23.0 g mol−-1 ; Cl = 35.5 g mol−-1]
A 36 m mol L−-1
B 36 mol L−-1
C 1440 mol L−-1
D 1440 m mol L−-1
Correct Answer
Option D
Solution

Data is insufficient.

Q43
For micelle formation, which of the following statements are correct? A. Micelle formation is an exothermic process. B. Micelle formation is an endothermic process. C. The entropy change is positive. D. The entropy change is negative.
A A and D only
B A and C only
C B and C only
D B and D only
Correct Answer
Option C
Solution

Micelle formation is an endothermic process with positive entropy change.

Q44
Statement I : For colloidal particles, the values of colligative properties are of small order as compared to values shown by true solutions at same concentration. Statement II : For colloidal particles, the potential difference between the fixed layer and the diffused layer of same charges is called the electrokinetic potential or zeta potential. In the light of the above statements, choose the correct answer from the options given below
A Both Statement I and Statement II are false
B Statement I is true and Statement II is false
C Both Statement I and Statement II are true
D Statement I is false but Statement II is true
Correct Answer
Option B
Solution

Statement I: For colloidal particles, the values of colligative properties are of small order as compared to values shown by true solutions at the same concentration.

This statement is true.

Colloidal particles are intermediate in size between true solutions and suspensions, and their properties differ from those of true solutions.

The colligative properties of colloids, such as osmotic pressure and vapor pressure, are of a smaller order of magnitude than those of true solutions with the same concentration.

Statement II: For colloidal particles, the potential difference between the fixed layer and the diffused layer of same charges is called the electrokinetic potential or zeta potential.

This statement is false.

For colloidal particles, the potential difference between the fixed layer and the diffused layer of opposite charges is called the electrokinetic potential or zeta potential.

Q45
Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : The diameter of colloidal particles in solution should not be much smaller than wavelength of light to show Tyndall effect. Reason R : The light scatters in all directions when the size of particles is large enough. In the light of the above statements, choose the correct answer from the options given below:
A Both A and R are correct and R is the correct explanation of A
B A is true but R is false
C Both A and R are correct but R is NOT the correct explanation of A
D A is false but R is true
Correct Answer
Option A
Solution

Tyndall effect is observed only when the following two conditions are satisfied (a) The diameter of the dispersed particle is not much smaller than the wave length of light used. (b) Refractive indices of dispersed phase and dispersion medium differ greatly in magnitude.

Q46
What happens when a lyophilic sol is added to a lyophobic sol?
A Film of lyophobic sol is formed over lyophilic sol.
B Lyophilic sol is dispersed in lyophobic sol.
C Film of lyophilic sol is formed over lyophobic sol.
D Lyophobic sol is coagulated
Correct Answer
Option C
Solution

When a lyophilic sol is added to a lyophobic sol, the lyophilic sol forms a protective film around the lyophobic sol particles, preventing their aggregation or coagulation.

This process is known as "protection" and is used to stabilize lyophobic sols.

Q47
Ferric chloride is applied to stop bleeding because -
A FeCl3\mathrm{FeCl}_{3} reacts with the constituents of blood which is a positively charged sol.
B Blood absorbs FeCl3\mathrm{FeCl}_{3} and forms a complex.
C Cl−\mathrm{Cl}^{-} ions cause coagulation of blood.
D Fe3+\mathrm{Fe}^{3+} ions coagulate blood which is a negatively charged sol.
Correct Answer
Option D
Solution

The correct answer is Option D: Fe3+ ions coagulate blood which is a negatively charged sol.

Blood is a colloidal solution, which means that it is made up of small particles suspended in a liquid.

The particles in blood are negatively charged, and the negative charge prevents the particles from clumping together.

When ferric chloride is applied to a bleeding wound, the Fe3+ ions in the ferric chloride react with the negatively charged particles in the blood.

This reaction causes the particles to clump together, forming a clot that stops the bleeding.

The other options are incorrect: Option A is incorrect.

Blood is not a positively charged sol.

Option B is incorrect.

Blood does not absorb ferric chloride.

Option C is incorrect.

Cl- ions do not cause coagulation of blood.

Q48

Match the catalysts (Column I) with products (Column II). .tg .tg Column I Column II

List - IList - II
(A) V2O5 (i) Polyethylene
(B) TiCl4/Al(Me)3 (ii) ethanal
(C) PdCl2 (iii) H2SO4
(D) Iron Oxide (iv) NH3
A (A)-(iii); (B)-(i); (C)-(ii); (D)-(iv)
B (A)-(ii); (B)-(iii); (C)-(i); (D)-(iv)
C (A)-(iii); (B)-(iv); (C)-(i); (D)-(ii)
D (A)-(iv); (B)-(iii); (C)-(ii); (D)-(i)
Correct Answer
Option A
Solution

(A) V2O5 is used for preparation of H2SO4 in contacts process.

(B) TiCl4 + Al(Me)3 this mixture is called Ziegler-Natta catalyst which is used in the synthesis of high density polyethene from ethene.

(C) PdCl2 is used in ethanol formation (D) Iron oxide is used in Haber process for NH3.

Q49
Given .tg .tg Gas H2 CH4 CO2 SO2 Critical Temperature / K 33 190 304 630 On the basis of data given above, predict which of the following gases shows least adsorption on a definite amount of charcoal ?
A SO2
B CH4
C H2
D CO2
Correct Answer
Option C
Solution

Adsorption ∝\propto Tc Therefore, H2 gas shows least adsorption on a definite amount of charcoal.

Q50
Given below are the critical temperatures of some of the gases: .tg .tg Gas Critical temperature (K) He 5.2 CH4_4 190.0 CO2_2 304.2 NH3_3 405.5 The gas showing least adsorption on a definite amount of charcoal is
A He
B CH4_4
C CO2_2
D NH3_3
Correct Answer
Option A
Solution

The greater the value of critical temperature greater is adsorption as He has the least critical temperature so it adsorb least.

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