Ketan Karkare

Let's take palladium hydride as an example. One volume of palladium can absorb 900 volumes of H2. This is not an ionic hydride like, for example, CaH2, but an alloy of palladium with metallic hydrogen. Therefore, the hydrogen content is determined by x= [H]/[Pd]. I hope you know how to convert the volume of gases into weight units. This is studied in the school curriculum in physics and chemistry. Thermal effects in these processes are not calculated. They are determined on calorimeters. You can look in the literature for a specific process. Perhaps the thermal effect that you need has already been determined.

Hello

To explain my answer I propose you what guided it;

It is difficult to know on which form the hydrogen is in the metal, that is to say it is in hydride form, atomic or molecular. The next difficulty is to measure its concentration. I approached these questions by studying the adsorption of incondensable gases on metals, atomically clean (Ta and Al (111)) at very low H2 partial pressure, of the order of 10^-3 Pascal and at room temperature. While the residence time of the molecules should be extremely short of the order of 10^- 10 seconds or less, it is much larger and depends on the polarity of the molecules and the presence of defects, impurities and dislocations. These defects create local variations of the crystal field and internal stresses while the adsorbed molecules create image charges that modify the electronic and vibrational structure at the surface of the solid. This is verified by electron spectrometry and is expressed by the dielectric function. Even at very low coverage, the adsorbed molecules become unstable due to the relaxation of internal stresses of entropic origin. This scheme is parallel to that of the effects of adsorbed charges on insulators and is expressed by an equation of state and expresses the surface barrier deformation by defects and the resulting physical/chemical adsorption and ion diffusion processes. On the basis of these elements, the hydrogen concentration of the order of ppm would not be measurable by weight but fatal to the cohesion. One can imagine several experiments to verify this scheme.

Have a nice day

Claude