A 1.0 mm thick and 10 cm x 10 cm large sheet of iron separates two gas com partm
ID: 1075709 • Letter: A
Question
A 1.0 mm thick and 10 cm x 10 cm large sheet of iron separates two gas com partments at 350°C. One compartment contains hydrogen. The pressure of H2 is maintained at 0.5 atm. The other compartment is maintained essentially free of hydrogen with an oxidizing gas present. It is well established that hydrogen dissolves into metals atomically. From the literature you know that for a partial pressure of H2 in the gas phase, the concentration of H atoms in iron is 0.0002 wt% at 350°C. The density of iron is 7.86 g/cm3. Assume furthermore that the hydrogen diffusion coefficient in iron is 6- 10-5 cm2/s independent of the hydro- gen concentration. Calculate the amount of H2 (number of moles) that is trans- ported through the iron sheet in 1 hour.Explanation / Answer
Volume of Fe sheet=1*10-3m*10*10-2m*10*10-2m =1*10-7*102m3=1*10-5m3
Iron weight =1*10-5m3*7.86*106gm-3=78.6g
Total H2 weight =78.6g*0.0001*10-2=7.86*10-5g
Total H2 moles = 7.86*10-5g/2gmol-1= 3.93*10-6mol
Diffused H2 Volume per hour=6*10-5*10-4m2/s*1*10-3m*60*60s=2.16*10-8m3
Diffused H2 moles (n) =PV/RT=(0.5*105 Nm-2*2.16*10-8m3)/(8.314Nmmol-1K-1)*623K=2.0851*10-7mol
Transported H2 moles = 3.93*10-6mol-2.0851*10-7mol=39.3*10-7mol-2.0851*10-7mol=3.721*10-6mol
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