Processes at Solid Surfaces Assignment Help

Processes at Solid Surfaces Assignment Help

Processes at Solid Surfaces

A 1.0-g sample of a hydrogenation catalyst adsorbs 125 mL (V) of |

hydrogen gas at 1.00 atm (P) and 298 K (7). What is the surface area

(A) of the catalyst? Assume the hydrogen molecules form a monolayer

and that each hydrogen molecule covers 1.3 x 107!? m2.

Nitrogen gas will adsorb on a silica gel surface. At 273 K and 1.00 atm, ©

the volume of nitrogen gas required to form a monolayer on the silica

gel is 0.129 L g™’. Assuming each nitrogen molecule occupies 1.62 x

10~’? m? of the surface, what is the surface area per gram of gel (A)? At

273 K and 1.00 atm, the molar volume of nitrogen gas is 22.4 L mol. –

A clean metal surface was exposed to ammonia gas for 1 s at 298 K (7).

The surface area was 1.00 cm?, and there were 5.0 x 10!° adsorption sites

available per square centimeter. The partial pressure of the ammonia was

2.0 x 10 torr (P). What percentage of the sites was occupied after 1 s?

Assume that all molecules striking the surface were adsorbed.

Oxygen gas will rapidly oxidize a freshly exposed calcium surface to

form CaO. A calcium surface with 2.0 x 10! calcium atoms is exposed

to oxygen gas at a partial pressure of 1.2 x 10~ Pa (P) at 298 K (7).

How long will it take the surface to oxidize completely? Assume there

is an average of one oxidation per collision.

The pressure (P) in an ultrahigh vacuum system is 7.0 x 1078 Pa.

Calculate the number (/,)) of argon atoms striking a square centimeter

of the surface each second at 273 K (7).

At 298 K (7), a pressure (P) of 3.0 x 10~ Pa is necessary to halfsaturate a silica gel surface with oxygen gas. Assume the enthalpy of

adsorption (AH,,,) is —10.8 kJ mol”! and the sticking coefficient (s”) is

unity. Determine the value of the desorption rate constant (fy).

88 » McGraw-Hill’s 500 Physical Chemistry Questions

495. The following table shows the relationship between the volume (V)

(adjusted to 0°C and 1 bar) of methane gas adsorbed per gram of activated

charcoal at a series of pressures. Assuming the data fit the Langmuir

isotherm, what are the values of the constants?

P (atm) 0.0474 0.0697 0.100 0.134 0.174 0.225 0.283 0.355

Viem@g) 14154 1842 22:85 26169 30:45 3435 38.03 41.65

496. Ethane will adsorb on an activated charcoal surface. The adsorption

constant (