Surface Chemistry(12th Grade > Chemistry ) Questions and answers for exam Preparation

12th Grade > Chemistry

SURFACE CHEMISTRY MCQs

Total Questions : 30 | Page 2 of 3 pages

Question 11. Arrange the following in the decreasing order of their coagulation power:

A l^{3 +}, N a^{+}, C a^{2 +}

Al3+=Ca2+=Na+
Na+>Ca2+>Al3+
Na+>Al3+>Ca2+
Al3+>Ca2+>Na+

Discuss Question

Answer: Option D. -> Al3+>Ca2+>Na+
:
D
Greater the valency of the flocculating ion added, greater is its power to cause precipitation (Hardy Schulze rule).

Question 12. Silver iodide is used in bringing about artificial rain because silver iodide

is easily decomposed in presence of sunlight
contains iodide ions which are large in size
has crystal structure similar to ice and leads to coagulation
being heavy, its spray brings the water droplets down

Discuss Question

Answer: Option C. -> has crystal structure similar to ice and leads to coagulation
:
C

A g^{+} I^{-}

ions brings about coagulation of water droplets easily.

Question 13. Milk can be preserved by adding a few drops of

Formic acid solution
Formaldehyde solution
Acetic acid solution
Acetaldehyde solution

Discuss Question

Answer: Option B. -> Formaldehyde solution
:
B
Formaldehyde is an emulsifier

Question 14. Which of the following factors are responsible for the stability of lyophilic sols?

Charge on the colloidal particles
Solvation of colloidal particles
Both a and b
None of the above

Discuss Question

Answer: Option C. -> Both a and b
:
C
The two factors responsible for the stability of the lyophilic sols are the charge and solvation of the colloidal particles.

Question 15.

10^{- 4}

g of gelatin is required to be added to 100

c m^{3}

of a stanadard gold solution to just prevent its precipitation by addition of 1

c m^{3}

of 10% NaCl solution to it. Hence, gold number of gelatin is?

10
1
0.1
0.01

Discuss Question

Answer: Option D. -> 0.01
:
D

10^{- 4} g = 0.1 m g

100 c m^{3}

of gold sol require 0.1 mg

∴ 10 c m^{3}

of gold sol will required 0.01 mg
Hence, gold number = 0.01.

Question 16. Glutamic acid

H_{2} N - C H (C H_{2} C H_{2} C O O H) - C O O H N

has

p K_{a 1} (α - C O O H) = 2.2, p K a 2 (R g r o u p C O O H) = 4.3

. The isoelectric point of glutamic acid is

5.9
7.0
10.2
3.2

Discuss Question

Answer: Option D. -> 3.2
:
D

H_{3} + N - C H | C H_{2} C H_{2} C O O H C a t i o n i c f o r m - C O O H O n n e u t r a l i s a t i o n ⟶ 1 s t i o n i z a t i o n H_{3} + N - C H | C H_{2} C H_{2} C O O H - C O O^{-} ⟶ 2 n d i o n i z a t i o n H_{3} + N - C H | C H_{2} C H_{2} C O O^{-} - C O O^{-}

I s o e l e c t r i c p o i n (p I) = \frac{p K_{a_{1}} + p K_{a_{3}}}{2}

\frac{2.2 + 4.3}{2} = 3.25

Question 17. The volume of colloidal particle

V_{c}

as comapred to the volume of solute particle in a true solution

V_{s}

could be

VcVs=1
VcVs=1023
VcVs=10−3
VcVs=103

Discuss Question

Answer: Option D. -> VcVs=103
:
D
Diameter of colloidal particle is about 10 times larger than solute particles in a true solution. Hence, volume is about 1000 times greater i.e.

\frac{V_{c}}{V_{s}} = 10^{3}

Question 18. Which of the following is an example of oil dispersed in water emulsion:

Butter
Milk
Cream
None of the above

Discuss Question

Answer: Option B. -> Milk
:
B
In milk, liquid fat is dispersed in water.

Question 19. Zeta potential ( or electrokinetic potential ) is the

potential required to bring about coagulation of a colloidal sol
potential required to give the particles a speed of 1 cm/ sec in the sol
potential difference between fixed charged layer and diffused layer having opposite charge
potential energy of colloidal particles

Discuss Question

Answer: Option C. -> potential difference between fixed charged layer and diffused layer having opposite charge
:
C
Zeta potential is the potential difference between fixed charge layer and diffused layer having opposite charge

Question 20. Ferric chloride is added to stop bleeding because