Surfaces and Interfaces - Physical Chemistry - Chemistry Previous Year Questions

1

2013 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2013

At 273 K and 10 bar, the Langmuir adsorption of a gas on a solid surface gave the fraction of surface coverage as 0.01. The Langmuir adsorption isotherm constant is ______ bar−1. (Give the answer to the third decimal place)

A

B

C

D

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2

2014 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2014

A monoatomic gas, X, adsorbed on a surface, follows Langmuir adsorption isotherm. A plot of the fraction of surface coverage, θ, against the concentration of the gas [X], for VERY LOW concentration of the gas, is described by the equation

A

θ = K[X]

B

1 − θ = \(\frac{1}{K[X]} \)

C

θ = K^1/2[X]^1/2

D

θ = \(\frac{K[X]}{1 - K[X]} \)

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3

2016 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2016

Adsorption of CO on charcoal at 273 K follows Langmuir isotherm. A plot of P (kPa) / V (cm³) versus P (kPa) is linear with a slope of 0.01 and y-intercept of 0.5. The equilibrium constant, K (kPa⁻¹), for the adsorption is ________.

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4

2019 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2019

In Freundlich isotherm, a linear relationship is obtained in the plot of
(θ = surface coverage and p = partial pressure of the gas)

A

θ vs p

B

ln(θ) vs ln(p)

C

ln(θ) vs p

D

θ vs ln(p)

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5

2019 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2019

Micelle formation is accompanied by the

A

decrease in overall entropy due to ordering.

B

increase in overall entropy mostly due to increase in solvent entropy.

C

increase in overall entropy mostly due to increase in solute entropy.

D

increase in overall entropy and decrease in enthalpy.

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6

2024 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2024

The non-dissociative adsorption of a gas on a given surface at a fixed temperature follows Langmuir isotherm. The plot(s) which give(s) a straight line is (are)
[Given: \(V\) = volume of the adsorbed gas, \(P\) = pressure of the gas]

A

\(1/V\) versus \(1/P\)

B

\(P/V\) versus \(P\)

C

\(V\) versus \(P\)

D

\(V\) versus \(1/P\)

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7

2015 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2015

The process given below follows the Langmuir adsorption isotherm. $A_2(g) \underset{k_{-1}}{\stackrel{k_1}{\rightleftharpoons}} 2 A_{ads}$ If \(\theta\) denotes the surface coverage and \(P\) denotes the pressure, the slope of the plot of \(1/\theta\) versus \(1/\sqrt{P}\) is

A

\(1/(K_{eq})^2\)

B

\(1/K_{eq}\)

C

\(-1/K_{eq}\)

D

\(1/(K_{eq})^{1/2}\)

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8

2017 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2017

The dissociative chemisorption of X₂(g) on a metal surface follows Langmuir adsorption isotherm. The ratio of the rate constants of the adsorption and desorption processes is 4.0 atm^-1. The fractional surface coverage of X(adsorbed) at 1.0 atm pressure is ________________________ (up to two decimal places)

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9

2018 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2018

For an ionic micelle-forming surfactant near its critical micelle concentration (CMC), the dependence of molar conductivity and surface tension on surfactant concentration is best represented by

A

B

C

D

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10

2018 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2018

For low partial pressure of ozone (\(O_3\)), the adsorption of ozone on graphite surface is fully dissociative in nature, and follows Langmuir isotherm. Under these conditions, if the dependence of the surface coverage of graphite (\(\theta\)) on partial pressure of ozone (\(P_{O_3}\)) is given by \(\theta \propto (P_{O_3})^x\), the value of \(x\) is __________. (Up to two decimal places)

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11

2020 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2020

Adsorption of N$_2$ on TiO$_2$ was carried out at 75 K. A plot of $\frac{z}{(1-z)}$ versus z (z = p/p$^0$) gives a straight line with an intercept, 4.0 × 10$^{-5}$ mm$^{-3}$ and slope, 1.0 × 10$^{-3}$ mm$^{-3}$. The volume (rounded off to the nearest integer) corresponding to the monolayer coverage is:

A

996 mm$^3$

B

785 mm$^3$

C

690 mm$^3$

D

555 mm$^3$

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12

2022 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2022

Adsorption of a gas with pressure P on a solid obeys the Langmuir adsorption isotherm. For a fixed fractional coverage, the correct relation between K and P at a fixed temperature is
[K = k_a/k_b, k_a and k_b are the rate constants for adsorption and desorption, respectively. Assume non-dissociative adsorption.]

A

K ∝ P^–1/2

B

K ∝ P

C

K ∝ P^–1

D

K ∝ P^1/2

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13

2026 · Chemistry · Physical Chemistry · Surfaces and Interfaces

Chemistry (CY) 2026

The correct statement(s) for a surface catalyzed unimolecular gaseous reaction is(are)

A

It follows Freundlich adsorption isotherm

B

Zero order kinetics is followed at sufficiently high pressure of the reacting molecules

C

First order kinetics is followed at very low pressure of the reacting molecules

D

Rate of the reaction is proportional to the fraction of surface covered by the reacting molecules

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