Discuss with the aid of a potential-energy diagram

Assignment Help Other Engineering

Reference no: EM131266571

The Fundamentals of Adsorption

1. The first eight problems are linked to the content of this chapter. To tackle the remainder, the reader is recommended to consult either some later chapters or the relevant reference cited.

Discuss with the aid of a potential-energy diagram, the process of dissociative chemisorptions of a diatomic gas at a metal surface. What relationship exists between the enthalpy of chemisorptions and the activation energy of desorption?

Thermal desorption spectra of atomic oxygen bound to the surface of a ruthenium catalyst show symmetrical peaks with a characteristic shift to lower temperatures at higher initial coverage, suggesting second-order kinetics. Using the data given in the table, confirm the reaction order and estimate the activation energy of desorption.

Relative desorption rate (peak height)	Coverage	Temperature(^oC)
0.83	1	448
1.6	0.92	468
2.07	0.8	476
2.93	0.66	494
2.4	0.32	522
0.89	0.14	540
0.13	0.04	548

2. At a temperature of 190 k and a pressure of CO of 48 Torr, 1/10th of a monolayer of adsorbate is present ate a nobale metal surface. At 250 k a partial pressure of 320 Torr is required at a noble metal surface. At 250 k a partial pressure of 320 Torr is required to achieve the same surface coverage. Estimate the molar enthalpy of adsorption, and comment upon whether the gas is likely to be physically adsorbed or chemisorbed. What other measurements would you perform to identify the nature of the adsorption?

3. It is alleged that the desorption of xenon from a graphite surface obeys zero-order kinetics (as does the desorption of certain metals from the surface of silicon). How would you (i) establish experimentally that this is indeed so and (ii) interpret such a result?

4. Estimate how long it would take to cover an atomically clean surface of a nickel catalyst with a monolayer of oxide if it were exposed to O₂ at a pressure of(a) 7.60 x10^-4 Torr or 1.33 x 10^-8 Pa, or (c) to a good laboratory vacuum.

5. What information can you glean from the following sets of data?
a) Acidic mordenite takes up the following amounts x of n-hexane as a function of pressure p at a temperature of 100^oC.

x(mmol g^-1)	p(Torr)
0.531	4.4
0.555	10.8
0.587	21.2
0.6	41.5
0.607	54.6
0.612	57.4

b) A pillared clay catalyst takes up the following amounts of N₂at 78K:

102 g g^-1	p(Torr)
7.63	21.1
8.75	130.9
9.05	195
9.46	287.2
10	422.4
11	490.3
9.6	276.6
9.1	159
7.95	31.8
7.19	9.4

6. It is known that the enthalpies of adsorption of an atom bound to sites at (a) a flat surface, (b) a ledge site and (c) a kink site are, respectively, 10, 20 and 30 kcal mo1^-1 (42, 84 and 126 kJ mo1^-1). Estimate the residence time of the atom on each of these sites at 300 K.

7 From the information in the table below pertaining to the adsorption of CO on Ca²⁺ -exchanged zeolite-Y, determine the isosteric heats of adsorption at each of the coverages.

T(k)	Pressure(N m^-2)
	Amount Adsorbed (106 m³ g^-1)
	0.05	0.1	0.2	0.4	0.6
273		15.2	34.2	116.2	310.5
290.3		40	100	356.2	834.3
304.4	28.6	80	247.6
322.6	914.4	247.6	685.7

This table has been compiled from Figure 4 of Egerton and Stone (1970).

These workers establish that CO is a sensitive probe molecule for investigating the location of unshielded multivalent cations in zeolitic catalysts.

Reference no: EM131266571

Questions Cloud

What should we do to the forecast model : What does this mean? What should we do to the forecast model to improve the situation?

Analyze why the company maintains the level of success : Analyze why this company maintains the level of success it does from an economic and financial perspective. Develop at least two visual aids (e.g., charts, graphs, or tables) to support your argument.

Role of relationship marketing and strategic alliances : Discuss the role of relationship marketing and strategic alliances in business marketing. - Why is relationship or personal selling the best way to promote in business marketing?

Regarding governmental and nonprofit accounting : When do GASB standards require interfund receivables and payables to be reported as Internal Balances? What are regulatory accounting principles and how do they relate to enterprise fund accounting?

Discuss with the aid of a potential-energy diagram : Discuss with the aid of a potential-energy diagram, the process of dissociative chemisorptions of a diatomic gas at a metal surface. What relationship exists between the enthalpy of chemisorptions and the activation energy of desorption?

Understand manner in which cabinet appointees are selected : Understanding the manner in which cabinet appointees are selected and the role that they serve, do you believe that they should primarily support and advocate for the policy positions of the President

Define a target market and develop a marketing plan : How could you use the Web site BtoBonline.com to help define a target market and develop a marketing plan?- How could you use the Internet in your business marketing of Huggies diapers?

Transformational and transactional leadership : Carefully review the concepts and definitions of charismatic, transformational, and transactional leadership. Then write a three-page paper addressing the following issues, using specific examples from your personal experiences. Make sure to cite ..

Inventory by the conventional retail inventory method : Presented below is information related to Oriole Company. Compute the inventory by the conventional retail inventory method.

User Account

All Pages