Surface Chemistry Test

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Surface Chemistry Test - 37

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Weekly Quiz Competition

Question 1
1 / -0

At Critical Micell Concentration (CMC), the surfactant molecules:

A
dissociate

B
associate

C
become completely soluble

D
decompose

Solution

The critical Micelle Concentration (CMC) is the concentration of surfactants in a solution above which micelles form. Below the CMC, surfactants in solution adsorb to a surface, lowering the surface tension, or disperse eithin the bulk. There may be an occasional micelle formed below the CMC. Likewise, above the CMC, a very limited amount of added surfactants may enter the dispersed phase or adsorb onto an interface. However, above the CMC, the vast majority of added surfactant will form micelles.
Question 2
1 / -0

For Adsorption phenomenon:

A
$$\Delta H=+ve,\Delta S=-ve$$

B
$$\Delta H=-ve,\Delta S=+ve$$

C
$$\Delta H=-ve,\Delta S=-ve$$

D
$$\Delta H=+ve,\Delta S=+ve$$

Solution

Adsorption leads to a decrease in the residual forces on the surface of the adsorbent. This causes a decrease in the surface energy of the adsorbent. Therefore, adsorption is always exothermic and $$ \Delta H$$ is negative.
And for reaction to occur $$ \Delta G$$ should be negative so by equation $$\Delta G = \Delta H- T\Delta S $$, $$ \Delta S$$ should be negative.
Question 3
1 / -0

Which of the following statements is NOT TRUE in respect of hydrophilic sols?

A
They are quite stable and are not easily coagulated

B
There is considerable interaction between dispersed phase and dispersion medium (water)

C
The sol particles are hydrated

D
They are very sensitive to coagulation by a small concentration of electrolytes

Solution

They are quite stable and are not easily coagulated because of considerable interaction between the dispersed phase and the dispersion medium.

So, "They are very sensitive to coagulation by a small concentration of electrolytes" is not true.
Question 4
1 / -0

For the adsorption of a gas on a solid, the plot of log (x/m) versus log P linear with slope equal to:

A
K

B
log k

C
N

D
$$\dfrac { 1 }{ n } $$
Question 5
1 / -0

Which statement is incorrect for a catalyst?

A
It does not affect the equilibrium constant

B
It increases the proportion of products in less time

C
It decreases the activation energy of a reaction

D
It increases the free energy change for the reaction

Solution

The statement (D) is incorrect for a catalyst. The correct statement is, "It does not increase/decrease the free energy change for the reaction."
A catalyst does not affect the energies of reactants and products of the reaction and hence, the energies are same for both catalyzed and non-catalyzed reactions.
Question 6
1 / -0

The graph between log $$\dfrac { X }{ m }$$ v/s log P is straight-line inclined at an angle $$45^o$$ with intercept 0.30. What will be the rate of adsorption at pressure of 0.4 atm?

A
0.4

B
0.6

C
0.8

D
0.9

Solution

Slope in equation is $$\dfrac{1}{n}$$ = tan$$45^o$$ =1
Intercept is logk = 0.30, that implies k=2
Hence by equation $$\dfrac{x}{m} = kp^{1/n}$$
k=2, n=1 and p=0.4

$$\therefore$$ Rate of adsorption, x/m is 0.8.

Option C is correct.
Question 7
1 / -0

Which of the following catalysis is an example of negative catalysis?

A
$$\displaystyle 2SO_2 + O_2 \overset{V_2O_5}{\longrightarrow} 2SO_3$$

B
$$\displaystyle CHCl_3 + O_2 \overset{alcohol}{\longrightarrow} 2COCl_2 + 2HCl$$

C
$$\displaystyle 2KClO_3 \overset{MnO_2}{\underset{\Delta}{\longrightarrow}} 2KCl + 3O_2$$

D
$$\displaystyle CO + 3H_2 \overset{Ni}{\longrightarrow} CH_4 + H_2O$$

Solution

Catalyst alters the rate of reaction by altering activation energy of reaction.
It could be positive catalyst which increases rate and can be negative catalyst which decreases rate of reaction.
According to the given options A, C, D have positive catalysts but in option B alcohol ($$C_2H_5OH$$) is a negative catalyst for oxidation of $$CHCl_3$$ which prevents reaction of chloroform with oxygen to give $$COCl_2$$.
Question 8
1 / -0

Which of the following statements does not show correct difference between adsorption and absorption?

A
In adsorption, the substance is concentrated only at the surface while in absorption it is uniformly distributed in the bulk.

B
Adsorption is instantaneous while absorption is a slow process.

C
A substance can be adsorbed as well as absorbed simultaneously and the process is called sorption.

D
Only gases are adsorbed while solids and liquids are absorbed.
Solution
- The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed adsorption.
- In adsorption, the substance is concentrated only at the surface and does not penetrate through the surface to the bulk of the adsorbent, while in absorption, the substance is uniformly distributed throughout the bulk of the solid or absorbent.
- A distinction can be made between absorption and adsorption by taking an example of water vapour. Water vapours are absorbed by anhydrous calcium chloride but adsorbed by silica gel.
Question 9
1 / -0

Which of the following statements does not show correct difference between adsorption and absorption?

A
In adsorption, the substance is concentrated only at the surface while in absorption it is uniformly distributed in the bulk

B
Adsorption is instantaneous while absorption is a slow process

C
A substance can be adsorbed as well as absorbed simultaneously and the process is called sorption

D
Only gases are adsorbed while solids and liquids are absorbed

Solution

adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface.
The phenomenon of adsorption strictly refers to the existence of a higher concentration of any particular component at the surface of a liquid or a solid phase that is present in the bulk or interior.
For example, five types of interfaces can exist (i) gas-solid (ii) liquid-solid (iii) liquid-liquid, (iv) solid – solid and gas-solid.
So option d is not correct
Question 10
1 / -0

The substance used as an adsorbent in the column chromatography is:

A
$${Na}_{2}O$$

B
$${Na}_{2}{SO}_{4}$$

C
$${Al}_{2}{O}_{3}$$

D
alum

Solution

Answer:- (C) $${Al}_{2}{O}_{3}$$
The stationary phase or adsorbent in column chromatography is a solid. The most common stationary phase for column chromatography is silica gel, the next most common being alumina.

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Surface Chemistry Test - 37

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Surface Chemistry Test - 37

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SHARING IS CARING

Question 1

dissociate

associate

become completely soluble

decompose

Solution

Question 2

$$\Delta H=+ve,\Delta S=-ve$$

$$\Delta H=-ve,\Delta S=+ve$$

$$\Delta H=-ve,\Delta S=-ve$$

$$\Delta H=+ve,\Delta S=+ve$$

Solution

Question 3

They are quite stable and are not easily coagulated

There is considerable interaction between dispersed phase and dispersion medium (water)

The sol particles are hydrated

They are very sensitive to coagulation by a small concentration of electrolytes

Solution

Question 4

K

log k

N

$$\dfrac { 1 }{ n } $$

Question 5

It does not affect the equilibrium constant

It increases the proportion of products in less time

It decreases the activation energy of a reaction

It increases the free energy change for the reaction

Solution

Question 6

0.4

0.6

0.8

0.9

Solution

Question 7

$$\displaystyle 2SO_2 + O_2 \overset{V_2O_5}{\longrightarrow} 2SO_3$$

$$\displaystyle CHCl_3 + O_2 \overset{alcohol}{\longrightarrow} 2COCl_2 + 2HCl$$

$$\displaystyle 2KClO_3 \overset{MnO_2}{\underset{\Delta}{\longrightarrow}} 2KCl + 3O_2$$

$$\displaystyle CO + 3H_2 \overset{Ni}{\longrightarrow} CH_4 + H_2O$$

Solution

Question 8

In adsorption, the substance is concentrated only at the surface while in absorption it is uniformly distributed in the bulk.

Adsorption is instantaneous while absorption is a slow process.

A substance can be adsorbed as well as absorbed simultaneously and the process is called sorption.

Only gases are adsorbed while solids and liquids are absorbed.

Solution

Question 9

In adsorption, the substance is concentrated only at the surface while in absorption it is uniformly distributed in the bulk

Adsorption is instantaneous while absorption is a slow process

A substance can be adsorbed as well as absorbed simultaneously and the process is called sorption

Only gases are adsorbed while solids and liquids are absorbed

Solution

Question 10

$${Na}_{2}O$$

$${Na}_{2}{SO}_{4}$$

$${Al}_{2}{O}_{3}$$

alum

Solution

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