Question

5. Consider the absorption of hydrogen into molten aluminum at 750°C, according to the reaction; H2 = 2 H. in which hydrogen molecules are adsorbed and dissolve into liquid aluminum, in atomic form, according to Sieverts Law of solubility. Given that we know the solubility of hydrogen in molten aluminum at this temperature is lcc/100 gm of liquid aluminum for hydrogen at unit activity (PH2 = 1 atm), calculate this solubility in terms of ppm H (parts per million H on a wt% basis). If the actual concentration of hydrogen in aluminum is 1 ppm (wt) for a particular commercial casting operation, estimate the partial pressure of hydrogen that would be manifested immediately above the molten aluminum surface.

Answer 1

Answer Given partial pressure of H₂ = 1 atm Temperature - 750°c = 750+273= 1023k Volume absorbed = 1 cm3 Moles of H₂ absorbed - PV IX! RT 6.08218 1623 0.238 = 1.198105 Mass of H₂ absorbed = 2g/mol x 119 x 10 = 2.39405 g ppm wt% = 2.386105. 100 xl@ For diatomie molecules, according to slevert's law the correlation between. hydrogen content and hydrogen partial pressure is as following. 1. Cak (PH) 0.5 Where c is absorbed concentration, Phis hydrogen partial pressure of K is equlibrium constant 0.238 0.26 PH) → P4 = (0-26/0230) PH = 1.19 atm