Surface chemistry

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DYNAMIC CHEMISTRY POINT
Assignment No –1
Topic Name - Surface Chemistry
Surface chemistry
1. The process given follows the Langmuir adsorption isotherm
K1


 2 Aads
A2 ( g ) 

K 1
If Q denotes the surface coverage and P denotes the pressure, the slope of the plot
of 1/Q versus 1 P is:(a) 1
(b) 1
( K eq )2
(c) 1
K eq
(d) 1
K eq
( K eq )
1
2
2. A monatomic gas X, adsorbed on a surface, follows Longmuir adsorptions 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 equation:1
1
1
k[ x]
(a) Θ = K [x]
(b) 1   
(c)   K 2 [ x] 2
(d)   1 
k[ x]
1  k[ x]
3. For a reaction an a surface:-
At low pressure of H2, the rate is proportional to:1
(a) [H2]
(b) 1
(c) [ H 2 ] 2
[H2 ]
(d) 1
1
H2 
2
4. Hydrogen is adsorbed on many metal surfaces by dissociation ( s represent
A surface site)
If the pressure of H2 (P) is small, the fraction of surface covered by hydrogen is
proportional to:(a) P
(b) P2
5. Among the following :-
(c) P
1
2
(d) P
3
3
The variations of mass adsorbed with pressure for a monolayer and monolayer and
multilayer are represented by:H.O: - 28A/11, Ist Floor, Jia Sarai, Hauz Khas, Near IIT Delhi-16
Phone No.-011-69000403, 9810236711 -09599967768
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DYNAMIC CHEMISTRY POINT
Assignment No –1
Topic Name - Surface Chemistry
(a) A and C respectively
(c) C and A respectively
(b) A and B respectively
(d) B and A respectively
6. For the non dissociative Langmuir type adsorption of gas on a solid surface at a
particular temperature, the fraction of surface coverage is 0.6 at 30 bar. The
Langmuir isotherm constant ( in bar-1 units) at this temperature is:(a) 0.05
(b) 0.20
(c) 2.0
(d) 5.0
7. At 273k 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)
8. The volume a gas adsorbed on a solid surface is 10.0ml, 11.0 ml, 11.2ml, 14.5 ml
and 22.5 ml at 1.0, 2.0, 3.0, 4.0, and 5.0atm pressure, respectively. These data are
best respectively by:(a) Gibbs isotherm
(b) Langmuir isotherm
(c) Freundlich isotherm
(d) BET isotherm
9. The decomposition of NH3 on Mo surface follows Langmuir – Hinshelwood
mechanism. The decomposition was carried out at low pressure. The reduced to
10-4 torr i8n 10 minutes. The rate constant of decomposition of NH3 is:(a) 9.9 × 10-4 torr min-1
(b) 0.4606 min-1
(c) 9.9 × 10-3 torr min-1
(d) 0.693 min-1
10. With increase in temperature, the Gibbs free energy for the a adsorption of gas on
to a solid surface:(a) Becomes more positive from a positive value.
(b) Becomes more negative from a positive value.
(c) Becomes more positive from a negative value.
(d) Becomes more negative from a negative value
11. The adsorption of a gas on a solid surface exhibits the following isotherm. Which
one of the following statement is true?
(a) Heat of adsorption is independent of coverage.
(b) Adsorption is multilayer.
(c) Heat of adsorption varies monotonically with coverage.
(d) Heat of adsorption varies exponentially with coverage.
12. Which of the following is not correct regarding the adsorption of a gas on the
surface of a solid:(a) On increasing temperature, adsorption increases continuously.
H.O: - 28A/11, Ist Floor, Jia Sarai, Hauz Khas, Near IIT Delhi-16
Phone No.-011-69000403, 9810236711 -09599967768
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DYNAMIC CHEMISTRY POINT
Assignment No –1
Topic Name - Surface Chemistry
(b) Enthalpy and entropy change are negative.
(c) Adsorption is more for specific substance.
(d) It is a reversible reaction.
13. In physical adsorption, the forces associated are:(a) Ionic
(b) covalent
(c) Vander Waals
14. Reversible adsorption is:(a) Chemical adsorption
(b) physical adsorption
15. Rate of physiosorption in increases with:(a) decrease in temperature
(b) increase in temperature
(d) H - bonding
(c) both
(d) none
(c) decrease in pressure
(d) decrease in surface area
16. Which one of the following is an incorrect statement for physiosorption? 2
(a) It is a reversible process.
(b) It requires less head of adsorption.
(c) It requires activation energy.
(d) It takes place at low temperature.
17. Which among the following statement is false:(a) Increase of pressure increases the amount of adsorption.
(b) Increases of temperature may decrease the amount of adsorption.
(c) The adsorption may be monolayer or multilayered.
(d) Particle size of the adsorption will not affect the amount of adsorption.
18. The adsorption of a gas in described by the Langmuir isotherm with the
equilibrium constant K = 0.9 K Pa-1 at 250C. The pressure (in Kpa) at which the
fractional surface coverage is 0.95 is:- 2
(a) 1/11.1
(b) 21.1
(c) 11.10
(d) 42.2
19. Isothermal which has frictional coverage linearly, dependent on pressure at low
pressure but almost independent at high pressure in called.
(a) BET isotherm
(b) Langmuir isotherm
(c) Freundlich isotherm
(d) Timken isotherm
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Phone No.-011-69000403, 9810236711 -09599967768
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