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

12th Grade > Chemistry

SURFACE CHEMISTRY MCQs

Total Questions : 30 | Page 1 of 3 pages

Question 1. When an excess of a very dilute aqueous solution of KI is added to a very dilute aqueous solution of silver nitrate, the colloidal particles of silver iodide are associated with which of the following Helmholtz double layer?

AgI ¦ Ag+ ¦ I-
AgI ¦ K+ ¦ NO−3
AgI ¦ NO−3 ¦ K+
AgI ¦ I− ¦ K+

Discuss Question

Answer: Option D. -> AgI ¦ I− ¦ K+
:
D
As excess of KI has been added,

I^{-}

ions are adsorbed on AgI forming a layer ( and giving it a negative charge). It then attracts the counter ion

K^{+}

from the medium forming the second layer (diffused layer).

Question 2. Method of formation of solution is given in Column I. Match it with the type of solution given in Column II.
Column I Column II
(i) Sulphur vapours passed through cold water (p) Normal electrolyte solution
(ii) Soap mixed with water above critical micelle concentration (q) Multi molecular colloids
critical micelle concentration
(iii) White of egg whipped with water (r) Associated colloid
(iv) Soap mixed with water below (s) Macro molecular colloids
critical micelle concentration

i-q, ii-r, iii-s, iv-p
i-p, ii-q, iii-r, iv-s
i-q, ii-p, iii-s, iv-r
i-r, ii-s, iii-q, iv-p

Discuss Question

Answer: Option A. -> i-q, ii-r, iii-s, iv-p
:
A
Sulphur sol consists of particles containing a thousand or more of

S_{8}

molecules => Multi molecular colloids
Below CMC, soap with water behaves as a normal electrolyte and above CMC as associated colloid

Question 3. Which of the following does not affect the Brownian movement:

Nature of colloid
Size of the particles
Viscosity of the solution
None of the above

Discuss Question

Answer: Option A. -> Nature of colloid
:
A
This motion is independent of the nature of the colloid but depends on the size of the particles and viscosity of the solution.

Question 4. Which of the following statements are true about peptization? A. A colloidal sol is converted into precipitate B. It is done in the presence of a small electrolyte C. Charges develop on the precipitate during this process D. The charges developed during this process further breaks up into smaller particles of the size of colloids.

A,B,D
A,B,C
B,C,D
A,B,C,D

Discuss Question

Answer: Option C. -> B,C,D
:
C
During peptization, precipitate is converted into a colloidal sol by shaking it with dispersion medium in the presence of a small amount of electrolyte.

Question 5. Which of the following statements are false?
A. Freundlich adsorption isotherm holds good for all pressure ranges.
B. The force of attraction existing between the adsorbate and adsorbent are Vander Waal’s forces in case of chemisorption.
C. Adsorption is an endothermic process.
D. The extent of adsorption decreases with increase in temperature for a physiosorption process.

B,C,D
A,B,C
B,C
All are false

Discuss Question

Answer: Option B. -> A,B,C
:
B
A. Freundlich isotherm doesn't hold good at high pressures as it seems to attain saturation at high pressure.

Which Of The Following Statements Are False?A. Freundlich Ad...

B. Vander Waal's forces exit in case of physiosorption; in chemisorption chemical bonds are formed.
C. Adsorption is an exothermic process, as adsorption process is followed by release of heat.
D. This statement is true. Since adsorption is an exothermic process, so Le chatelier's principle explains this property.

Question 6. The flocculation value of an electrolyte is

The amount of electrolyte in grams required to bring about coagulation of one litre of colloidal sol
The amount of electrolyte in milligrams to bring about coagulation of 10ml of collodial sol
The amount of the electrolyte in millimoles required to bring about the coagulation of 1 litre of colloidal sol
The reciprocal of coagulating power

Discuss Question

Answer: Option C. -> The amount of the electrolyte in millimoles required to bring about the coagulation of 1 litre of colloidal sol
:
C
By definition

Question 7. Which among the following statement is false?
A. Chemisorption is reversible in nature
B. Particle size of adsorbent will not affect the amount of adsorption
C. Increase of pressure increases amount of adsorption
D. Increase of temperature always decreases the amount of adsorption

A,D
A,B,D
A
All are false

Discuss Question

Answer: Option B. -> A,B,D
:
B
A.It is irreversible in nature because of the formation of new bonds.
B.Surface area of a powdered solid adsorbent depends on its particle size. Smaller the particle size, greater is its surface area and hence more is the extent of adsorption.
C.Correct statement
D.In case of chemisorption isobar, it first increases and then decreases with increase in temperature.

Question 8. The equation for Freundlich adsorption isotherm is
a)

\frac{x}{m} = k p^{\frac{1}{n}}

(l n x) = l n (m k) + \frac{1}{n} l n p

\frac{x}{m} = k p^{- n}

d) Only a and b

Discuss Question

Answer: Option D. -> d
:
D
The equation is:

\frac{x}{m} = k p^{\frac{1}{n}} \Rightarrow l n (\frac{x}{m}) = l n k + (\frac{1}{n}) l n p \Rightarrow l n x - l n m k + (\frac{1}{n}) l n p

l n x = l n m + l n k + (\frac{1}{n}) l n p \Rightarrow l n x = l n m k + (\frac{1}{n}) l n p

Question 9. Which of the following options are correct?

Micelle formation by soap in aqueous solution is possible at all temperatures.
Micelle formation by soap in aqueous solution occurs above a particular concentration.
On dilution of soap solution micelles cannot revert to individual ions.
Soap solution behaves as a normal strong electrolyte at all concentrations.

Discuss Question

Answer: Option B. -> Micelle formation by soap in aqueous solution occurs above a particular concentration.
:
B
The formation of micelles takes place only above a particular temperature called ‘Krafft Temperature’ and only above a particular concentration called ‘Critical micelle concentration’.
On dilution of soap solution micelles revert to individual ions.

Question 10. In Ostwald’s process, oxidation of gaseous ammonia into nitric acid takes place in the presence of solid platinum gauze, which acts as the catalyst for this reaction. This is an example of:

Homogeneous catalysis
Heterogeneous catalysis
Both a and b
Cannot be determined

Discuss Question

Answer: Option B. -> Heterogeneous catalysis
:
B
Here the reactant is in gaseous phase while the catalyst is in solid phase. Since the two are in different phases, so this is an example of heterogeneous catalysis.