43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

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Chapter 19

Surface Chemistry - all with Video Answers

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Section 1

Topic 1 : Adsorption

Problem 1

Adsorption of a gas follows Freundlich adsorption isotherm. If $x$ is the mass of the gas adsorbed on mass $\mathrm{m}$ of the adsorbent, the correct
plot of $\underline{x}$ versus $p$ is :
$m$

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 2

Amongst the following statements regarding adsorption, those that are valid are :(1) $\Delta \mathrm{H}$ becomes less negative as adsorption proceeds.
(2) On a given adsorbent, ammonia is adsorbed more than nitrogen gas.
(3) On adsorption, the residual force acting along the surface of the adsorbent increases.
(4) With increase in temperature, the equilibrium concentration of adsorbate increases.
(a) (4) and (1)
(b) (2) and (3)
(c) (1) and (2)
(d) (3) and (4)

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 3

A mixture of gases $\mathrm{O}_{2}, \mathrm{H}_{2}$ and $\mathrm{CO}$ are taken in a closed vessel containing charcoal. The graph that represents the correct behaviour of pressure with time is:

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 4

Adsorption of a gas follows Freundlich adsorption isotherm. $x$ is the
mass of the gas adsorbed on mass $\mathrm{m}$ of the adsorbent. The plot of $\frac{x}{m}$
versus $\log p$ is shown in the given graph. $\frac{x}{m}$ is proportional to :(a) $p^{2 / 3}$
(b) $p^{3 / 2}$
(c) $p^{3}$
(d) $p^{2}$

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 5

Given gas critical temperature/ $\mathrm{K}$ for$\mathrm{H}_{2} \mathrm{CH}_{4} \mathrm{CO}_{2} \quad \mathrm{SO}_{2}$ is
$\begin{array}{llll}33 & 190 & 304 & 630\end{array}$
On the basis of data given above, predict which of the following gases shows least adsorption on a definite amount of charcoal?(a) $\mathrm{SO}_{2}$
(b) $\mathrm{CH}_{4}$
(c) $\mathrm{CO}_{2}$
(d) $\mathrm{H}_{2}$

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 6

If $x$ gram of gas is adsorbed by $m$ gram of adsorbent at pressure $P$, the
plot of $\log \frac{x}{m}$ versus $\log P$ is linear. The slope of the plot is: (n and $k$
are constants and $\mathrm{n}>1$ )(a) $\log \mathrm{k}$
(b) $\frac{1}{n}$
(c) $2 \mathrm{k}$
(d) $\mathrm{n}$

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 7

Adsorption of a gas on a surface follows Freundlich adsorption isotherm. Plot of $\log \frac{x}{m}$ versus $\log p$ gives a straight line with slope equal to $0.5$, then :( $\frac{x}{m}$ is the mass of the gas adsorbed per gram of adsorbent)(a) Adsorption is independent of pressure.
(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.

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 8

For a linear plot of $\log (x / m)$ versus $\log p$ in a Freundlich adsorption isotherm, which of the following statements is correct? ( $k$ and $n$ are constants).(a) Only $1 / n$ appears as the slope.
(b) $\log (1 / n)$ appears as the intercept.
(c) Both $k$ and $1 / n$ appear in the slope term.
(d) $1 / n$ appears as the intercept.

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 9

A particular adsorption process has the following characteristics : (i) It arises due to van der Waals forces and (ii) it is reversile. Identify the correct statement that describes the above adsorption process:(a) Adsorption is monolayer.
(b) Adsorption increases with increase in temperature.
(c) Enthalpy of adsorption is greater than $100 \mathrm{~kJ} \mathrm{~mol}^{-1}$
(d) Energy of activation is low.

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 10

The following statements relate to the adsorption of gases on a solid surface. Identify the incorrect statement among them :(a) Enthalpy of adsorption is negative
(b) Energy appears as heat
(c) On adsorption, the residual forces on the surface are increased
(d) Entropy of adsorption is negative

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 11

Methylene blue, from its aqueous solution, is adsorbed on activated charcoal at $25^{\circ} \mathrm{C}$. For this process, the correct statement is(a) The adsorption requires activation at $25^{\circ} \mathrm{C}$
(b) The adsorption is accompanied by a decrease in enthalpy
(c) The adsorption increases with increase of temperature
(d) The adsorption is irreversible

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 12

Adsorption of gases on solid surface is generally exothermic because(a) enthalpy is positive
(b) entropy decreases
(c) entropy increases
(d) free energy increases

Narayan Hari

Numerade Educator

Problem 13

Rate of physisorption increases with(a) decrease in temperature
(b) increase in temperature
(c) decrease in pressure
(d) decrease in surface area

Vishal Sharma

Numerade Educator

Problem 14

The mass of gas adsorbed, $x$, per unit mass of adsorbate, $m$, was measured at various pressures, $p .$ A graph between $\log \frac{x}{m}$ and $\log p$ gives a straight line with slope equal to 2 and the intercept equal to
$0.4771 .$ The value of $\frac{x}{m}$ at a pressure of $4 \mathrm{~atm}$ is : (Given $\log 3=$ $0.4771)$

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 15

$20 \%$ of surface sites are occupied by $\mathrm{N}_{2}$ molecules. The density of surface site is $6.023 \times 10^{14} \mathrm{~cm}^{-2}$ and total surface area is $1000 \mathrm{~cm}^{2}$. The catalyst is heated to $300 \mathrm{~K}$ while $\mathrm{N}_{2}$ is completely desorbed into a pressure of $0.001$ atm and volume of $2.46 \mathrm{~cm}^{3}$. Find the number of active sites occupied by each $\mathrm{N}_{2}$ molecule.

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 16

For Freundlich adsorption isotherm, a plot of $\log (x / \mathrm{m})(y$-axis) and $\log p$ ( $x$-axis) gives a straight line. The intercept and slope for the line is $0.4771$ and 2, respectively. The mass of gas, adsorbed per gram of adsorbent if the initial pressure is $0.04 \mathrm{~atm}$, is $\times 10^{-4} \mathrm{~g}$.

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 17

When $\mathrm{O}_{2}$ is adsorbed on a metallic surface, electron transfer occurs from the metal to $\mathrm{O}_{2}$. The true statement(s) regarding this adsorption is(are)(a) $\mathrm{O}_{2}$ is physisorbed
(b) Heat is released
(c) Occupancy of $\pi^{*} 2 \rho$ of $\mathrm{O}_{2}$ is increased
(d) Bond length of $\mathrm{O}_{2}$ is increased

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 18

The given graphs/data I, II, III and IV represent general trends observed for different physisorption and chemisorption processesunder mild conditions of temperature and presure. Which of the following choice(s) about I, II, III and IV is (are) correct?

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 19

The correct statement(s) pertaining to the adsorption of a gas on a solid surface is (are)(a) Adsorption is always exothermic
(b) Physisorption may transform into chemisorption at high temperature
(c) Physisorption increases with increasing temperature but chemisorption decreases with increasing temperature
(d) Chemisorption is more exothermic than physiosorption, however it is very slow due to higher energy of activation

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator

Problem 20

$\begin{array}{ll}1 \mathrm{~g} \text { of charcoal adsorbs } 100 \mathrm{~mL} & 0.5 \mathrm{M} \\ \mathrm{CH}_{3} \mathrm{COOH}\end{array}$ to form a
monolayer, and thereby the molarity of $\mathrm{CH}_{3} \mathrm{COOH}$ reduces to $0.49$. Calculate the surface area of the charcoal adsorbed by each molecule of acetic acid. Surface area of charcoal $=3.01 \times 10^{2} \mathrm{~m}^{2} / \mathrm{g}$.

Nikhil Choudhary

Nikhil Choudhary

Numerade Educator