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

12th Grade > Chemistry

SURFACE CHEMISTRY MCQs

Total Questions : 30 | Page 3 of 3 pages

Question 21. Which of the following properties of colloids involve scattering of lights?

Colligative properties
Tyndall effect
Brownian movement
None of the above

Discuss Question

Answer: Option B. -> Tyndall effect
:
B
The Tyndall effect is due to the fact that colloidal particles scatter light in all directions in space.

Question 22. Which of the following statement about zeolite is false?

They are used as cation exchangers
They have open structure which enables them to take up small molecules
Zeolites are aluminosilicates having three dimensional network
Some of the SiO4−4 units are repalced by AlO5−4 and AlO9−6- ions in zeolite

Discuss Question

Answer: Option D. -> Some of the SiO4−4 units are repalced by AlO5−4 and AlO9−6- ions in zeolite
:
D

A l O_{4}^{5 -}

ion has nearly the same size as the

S i O_{4}^{4 -}

ion and can replace the latter from silicates provided electrical neutrality is maintained.

Question 23. 50 ml of 1 M oxalic acid is shaken with 0.5 gm of wood charcoal. The final concentration of the solution after adsorption is 0.2 M. Amount of oxalic acid absorbed per gm of charcoal is (Use molar mass of hydrated oxalic acid = 126)

2.52 gm
6.30 gm
10.08 gm
None

Discuss Question

Answer: Option C. -> 10.08 gm
:
C
Initially weight of oxalic acid present =

W = \frac{126 \times 1 \times 50}{1000} = 6.3 g m

Finally weight of oxalic acid remaining =

W = \frac{126 \times 0.2 \times 50}{1000} = \frac{6.3}{5} g m

0.5 gm of charcoal adsorbed

6.3 \times (1 - \frac{1}{5}) = 6.3 \times (\frac{45}{)}

gm of oxalic acid
So, amount of oxalic acid adsorbed per gram of charcoal

= 2 \times (6.3 \times (\frac{4}{5})) = 10.08

Question 24. A negatively charged suspension of clay in water is needed for precipitation of minimum amount of -

Aluminium chloride
Potassium sulphate
Sodium hydroxide
Hydrochloric acid

Discuss Question

Answer: Option A. -> Aluminium chloride
:
A
A negatively charged clay suspension in water can be precipitated by minimum amount of

A l^{3 +} (A l C l_{3})

because

A l^{3 +}

ions have maximum opposite charge, i.e., +3 units

Question 25. For the most efficient functioning of enzymes which of the following statements is not correct

An optimum temperature is needed
An optimum pH is needed
They are substrate specific
They always increase activation energy

Discuss Question

Answer: Option D. -> They always increase activation energy
:
D
Enzymes do not increase activation energy.

Question 26. Reactions in Zeolite catalysts depend on -

Pores
Apertures
Size of cavities
All of these

Discuss Question

Answer: Option D. -> All of these
:
D
Zeolite is a shape-selective catalyst

Question 27. On the basis of data given below predict which of the following gases shows least adsorption on a definite amount of charcoal?
Gas Critical temp./K

C O_{2}

304

S O_{2}

630

C H_{4}

190

H_{2}

Discuss Question

Answer: Option D. -> H2
:
D
It has the least critical temperature

Question 28. The coagulation of 100ml of colloidal solution of gold is completely prevented by addition of 0.25g of a substance of X to it before adding 1ml of 10% NaCl solution. the gold number of "X" is-

0.25
25
250
2.5

Discuss Question

Answer: Option B. -> 25
:
B
250 mg of X prevents coagulation of 100 ml of colloidal sol of gold. By definition gold number of X is taht amount of it in mg which prevents coagulation of 10 ml of colloidal gold sol. Hence, to prevent coagulation of 10ml of gold sol, the amount of X required =25 mg, which is the gold number of X.

Question 29. The role of a catalyst in a reversible reaction is to

Increase the rate of forward reaction
Decrease the rate of backward reaction
Alter the equilibrium constant of the reaction
Allow the equilibrium to be achieved quickly

Discuss Question

Answer: Option D. -> Allow the equilibrium to be achieved quickly
:
D
An increase in rate of reaction in forward direction by a catalyst for a reaction in equilibrium brings in an increase in concentration of products and thus rate of backward reaction also increase to same magnitude and so allow the equilibrium to be achieved quickly.

Question 30. Which of the following forms cationic micelles above certain concentration?