CHEM 341 Spring 2023 Homework 3
Chapter 3
Name: ID:
Answer the following questions showing your detailed answers; formulas, calculations and units.
1. The adsorption of a gas is described by the Langmuir isotherm with K = 0.75 kPa−1 at 25 °C. Calculate the
pressure at which the fractional surface coverage is (i) 0.15, (ii) 0.95.
2. The volume of gas at 20 °C and 1.00 bar adsorbed on the surface of 1.50 g of a sample of silica at 0 °C was
1.52 cm3 at 56.4 kPa and 2.77 cm 3 at 108 kPa. Assume that the Langmuir isotherm applies and estimate the
value of Vm.
1
CHEM 341 Homework 3
, 3. The data below are for the chemisorption of H2 (g) on Cu powder at 25 °C.
P (Pa) Vads (cm3)
25 0.042
129 0.163
253 0.221
540 0.321
(a) Confirm that the data fit the Langmuir isotherm at low coverages.
(b) Calculate K for the adsorption equilibrium and the adsorption volume corresponding to complete
coverage.
a)
1/KVm KVm K
intercept
548.07 0.001825 0.003894
b) 1/Vm Vm
slope
2.134 0.468604
2
CHEM 341 Homework 3
Chapter 3
Name: ID:
Answer the following questions showing your detailed answers; formulas, calculations and units.
1. The adsorption of a gas is described by the Langmuir isotherm with K = 0.75 kPa−1 at 25 °C. Calculate the
pressure at which the fractional surface coverage is (i) 0.15, (ii) 0.95.
2. The volume of gas at 20 °C and 1.00 bar adsorbed on the surface of 1.50 g of a sample of silica at 0 °C was
1.52 cm3 at 56.4 kPa and 2.77 cm 3 at 108 kPa. Assume that the Langmuir isotherm applies and estimate the
value of Vm.
1
CHEM 341 Homework 3
, 3. The data below are for the chemisorption of H2 (g) on Cu powder at 25 °C.
P (Pa) Vads (cm3)
25 0.042
129 0.163
253 0.221
540 0.321
(a) Confirm that the data fit the Langmuir isotherm at low coverages.
(b) Calculate K for the adsorption equilibrium and the adsorption volume corresponding to complete
coverage.
a)
1/KVm KVm K
intercept
548.07 0.001825 0.003894
b) 1/Vm Vm
slope
2.134 0.468604
2
CHEM 341 Homework 3
