1

### AIPMT 2011 Prelims

If x is amount of adsorbate and m is amount of adsorbent, which of the following relations is not related to adsorption process?
A
x/m = $f$(p) at constant T
B
x/m = f(T) at constant p
C
p = f(T) at constant (x/m)
D
${x \over m} = p \times T$

## Explanation

${x \over m} = p \times T$ is incorrect.

2

### AIPMT 2007

The Langmuir adsorption isotherm is deduced using the assumption
A
the adsorption sites are equivalent in their ability to adsorb the particles
B
the heat of adsorption varies with coverage
C
the adsorbed molecules interact with each other
D
the adsorption takes place in multilayers.

## Explanation

Langmuir adsorption isotherm is based on the assumption that every adsorption site is equivalent and that the ability of a particle to bind there is independent of whether nearby sites are occupied or not occupied.
3

### AIPMT 2006

A plot of log(x/m) versus log p for the adsorption of a gas on a solid gives a straight line with slope equal to
A
log K
B
$-$ log K
C
n
D
1/n

## 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.
4

### AIPMT 2005

Which one of the following forms micelles in aqueous solution above certain concentration?
A
Dodecyl trimethyl ammonium chloride
B
Glucose
C
Urea
D
Pyridinium chloride

## Explanation

Dodecyl trimethyl ammonium chloride is a cationic surfactant and forms micelles in aqueous solution above critical micelle concentration (CMC). 