1

### JEE Main 2017 (Online) 8th April Morning Slot

Among the following, correct statement is :
A
Brownian movement is more pronounced for smaller particles than for bigger–particles
B
Sols of metal sulphides are lyophilic.
C
Hardy Schulze law states that bigger the size of the ions, the greater is its coagulating power.
D
One would expect charcoal to adsorb chlorine more than hydrogen sulphide.

## Explanation

(a)   Brownian motion caused by the bombardment of the particles by molecules of the median. In smaller particle the bombardment is not effective enough so that it can change it's direction and perform zig zag motion. But for bigger particle zig zag motion happens as bombardment is effective.

(b)    Inorganic sols are lyophobic. Metal sulphates are inorganic sols so it is lyophotic.

(c)    Hardly Schulze does not depends on the size of the ion it depends on the size of the ion it depends on the charge on the ion.

(d)   Molar mass of Cl2 is 71 and molar mass of H2S is 34 and in both the molecule Nanderwaal force of attraction present. As Cl2 has more mass than H2S So it's vanderwall force of attraction will be more and tendency to melt will also be more. So, Cl2 will get easily absorbed.
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### JEE Main 2017 (Online) 9th April Morning Slot

Adsorption of a gas on a surface follows Freundlich adsorption isotherm. Plot of log ${x \over m}$ versus log p gives a straight line with slope equal to 0.5, then:

( ${x \over m}$ is the mass of the gas adsorbed per gram of adsorbent)
A
B
Adsorption is proportional to the pressure.
C
Adsorption is proportional to the square root of pressure.
D
Adsorption is proportional to the square of pressure.

## Explanation

According to Freundlich adsorption isotherm, in the median range of pressure

${x \over m} \propto {P^{{1 \over n}}}$

$\Rightarrow$  ${x \over m}$ = kP$^{{1 \over n}}$

taking log both sides, we get,

log${x \over m}$ = logk + ${1 \over n}$ logP

Here in graph between log${x \over m}$ and logP, slope is ${1 \over n}$ and intercepts = log k.

Given that,

slope = 0.5

$\therefore\,\,\,$ ${1 \over n}$ = 0.5

$\Rightarrow$   n = 2

$\therefore\,\,\,$ ${x \over m}$ = kP$^{{1 \over 2}}$ = k$\sqrt P$

$\therefore$  Adsorption is proportional to the square root of pressure.
3

### JEE Main 2018 (Offline)

Which type of ‘defect’ has the presence of cations in the interstitial sites?
A
Metal deficiency defect
B
Schottky defect
C
Vacancy defect
D
Frenkel defect

## Explanation

In Frenkel defect in a molecule an atom or ion (normally the cation) leave their original site and places itself in the interstitial site (area between all other cations and anions). Which is shown below 4

### JEE Main 2018 (Online) 15th April Morning Slot

Which of the following statements about colloids is False ?
A
Freezing point of colloidal solution is lower than true solution at same concentration of a solute.
B
Colloidal particles can pass through ordinary filter paper.
C
When silver nitrate solution is added to potassium iodide solution, a negatively charged colloidal solution is formed.
D
When excess of electolyte is added to colloidal solution, colloidal particle will be precipitated.

## Explanation

Freezing point of colloidal solution is same as true solution at same concentration of a solute.