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QUESTION: 1

Calculate how long a hydrogen atom will remains on the surface of a solid at 1000 K if its desorption activation energy is 15 kJ mol and assume that

Solution:

According to desorption activation energy:

QUESTION: 2

The volume of gases NH_{3}, CO_{2} and H_{2} gas adsorbed by 1 gm charcoal at 300 K lie in the order ?

Solution:

More readily soluble and easily liquifiable gases such as NH_{3}/HC1/C1_{2} and SO_{2}, are adsorbed more than H_{2}/N_{2}.

i.e.. adsorption

proportional to intemiolecular interaction,

proportional to molecular mass,

proportional to ease of liquidation,

proportional to 'a’.

proportional to ciitical temperature (T_{e}.

Therefore, order of adsoiption of gases:

SO_{2} > NH_{3} > HC1 > CO_{2}, > CH_{4} > CO > N_{2} > H_{2}

*Answer can only contain numeric values

QUESTION: 3

The adsorption of a gas an a solid surface was found to follow a langmuir isotherm with K = 4 Pa^{-1} at a temp of 25 °C. The pressure of a gas required to achieve a fractional surface coverage of 90 % is _____________________________ (in Pa), (upto two decimal places)

Solution:

QUESTION: 4

Which of the following factor's influencing the adsorption?

Solution:

QUESTION: 5

Following plot represents the varition of temperature T with pressure for a definite extent of adsorption (xin) is called

Solution:

QUESTION: 6

Which among the following statements are NOT collects w.r.t. adsorption of gases on a solid ?

Solution:

QUESTION: 7

Graph between log (x in) and log (P) is straight line at angle of 45° with intercept is 0.602 ?

The extent of adsorption (x in) at a pressure of 1 atm is

Solution:

According to Freundlich adsorption isotherm:

QUESTION: 8

Which of the following animation 's are correct in which B .E .T equation reduced into Langmuir ?

Solution:

B.E.T equation:

QUESTION: 9

Which of the inherent assumption in the Langmuir model of surface adsorption are ?

Solution:

QUESTION: 10

Following is the varition of physical as adsoiption with temperature ?

Solution:

QUESTION: 11

Which of the following plot does not corresponds to the adsorption isotherm ?

Solution:

Because:

(a) Amount of adsorption keeps on rising in each case with increase in pressure

E .g: Adsorptio n of Br_{2}, on silica get at 80°C

(b) Multilayer physical adsorption on non-porous solid.

E.g: Adsorption of N, on silica gel.

(c) Langmuir type isotherm.

E.g: H_{2} and N_{2} adsorbed on charcoal at 180 °C.

QUESTION: 12

The adsorption of a gas is described by the L angmuir adsorption isotherm with K = 0.3 kPa^{-1}. A t a pressure of 0.2 kPa. the if actional coverage is

Solution:

QUESTION: 13

Which of the following expression are CORRECT ?

Solution:

*Answer can only contain numeric values

QUESTION: 14

At 273 K, N_{2} is absorbed on a niica surface. A plot of ( V in m^{3} and P in torr) gives a straight line with a slope equal to 2x 10^{-5} torr m^{-3} and intercept equivalent to V_{m} is equal to 4 x 10^{-8} m^{3}. The ad solution coefficient is _____________________ x 10^{12} (torr^{-1}) ( upto two decimal places)

Solution:

As we know that.

Reverse the reactioin,

*Answer can only contain numeric values

QUESTION: 15

At 273 K, H_{2} is absorbed on a mica surface. A plot of vs P (V in m^{3} and P in Pa) gives a straight line with a slope equal to 2 cm^{-3} and intercept is 3x10^{-3 }cm^{-3} Pa respectively. The adsorption coefficient is ____________________ x 10^{3} Pa. (upto two decimal places)

Solution:

From Langmuir isotherm.

*Answer can only contain numeric values

QUESTION: 16

Calculate the adsorption of a dye on activated carbon at 25°C, where k = 0.025, n = 0.5 and C = 0.04.

Based on the Freundlich isotherm.

Solution:

Given data

n = 0.5

K_{d} = 0.025

C = 0.04

Substitute the values in the corresponding equation

q = K_{d} C_{(1/n)}

q = (0.025) (0.04)_{(1/0.5)}

q = 0.040.

QUESTION: 17

The time for which the oxygen atom remains adsorbed on a tungsten surface is 0.36 at 2550 K and 3.49 at 2360 K. Calculate the activation energy of desorption of oxygen atom.

Solution:

From integrated Arrhenius type equation:

QUESTION: 18

Ail organic fatty acid forms a surface film on water that obeys the two-Dimensional ideal gas law. If the surface tension lowering is 10 mNm^{-1} at 25°C. The surface area per adsorbed molecules is

Solution:

Surface film pressure equation (π) = τ_{2}RT

Surface excess concentration

Therefore, π = surface tension. N = number of molecules.

QUESTION: 19

An 18°C . the surface tension (γ) of an aqueous solution of butyric acid is represented by the equation γ = γ_{0 }-29 .8 log( 19.64 c_{2} + 1 ) where γ_{0} is surface tension of water is 0.0073 Nm^{-1} and c_{2 }is the bulk concentration of the solute. Using the Gibbs adsorption isotherm to estimate the surface excess of butyric acid at c_{2 }is equal to 0.01 mol dm^{-3}

Solution:

*Answer can only contain numeric values

QUESTION: 20

The number of molecules of CETANOL absorbate of cross-section area 2.58 x 10^{-19 }m^{2} can be observed on the surface of a spherical drop of dodecane of radius 17 .8 pm is ________________ x 10^{4}. (Round off to two decimal places)

Solution:

Area = 2.58 x 10^{-19}m^{2} (occupied by single molecules)

1= 17.8 nm= 17.8 x 10^{-9} m

Total surface area of docedane = 4 πr^{2}

= 4 x 3.14 x (17.8 x 10^{-9})^{2}

= 3.979 x 10^{-15} m^{2}

Therefore, total surface area = Area occupied by single molecules x Number of molecules

3.979 x 10^{-15} = 2.58x 10^{-19} x Number of molecules

Number of molecules =

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