I am studying the very BASIC introduction of catalysis in general chemistry and encountered an example of a heterogeneous catalyst, which is catalytic hydrogenation of alkene into alkane using Pt/C or Pd/C, I have some questions:

  1. why sometimes we need to use Pt, and sometimes we need to use Pd? Are there any differences in reactivity, or just purely depends on what is at hand?

  2. I know the addition of activated carbon powder is to increase the surface area between reactants and catalyst. However, the carbon powder isn't added all the time when doing different heterogeneous catalysis reactions, why is it so if it is beneficial?

  3. Bond dissociation energy of H2 = 436kJ/mol. But when H2 is adsorbed on the metal surface, the bond is broken. How come this simple step can break this strong bond? I suspect the metal-H bond formed is stronger than H-H bond, which means it is favorable, but I still have no idea where does the 436kJ/mol energy comes from.

Thanksenter image description here

  • $\begingroup$ Q3-Hydrogenation of Alkenes is an exothermic process. $\endgroup$
    – user102687
    Jan 20 at 16:19
  • $\begingroup$ Pt is rather more reactive than Pd as a catalyst so you might prefer to use Pd when there are other potentially reducible groups present. $\endgroup$
    – Waylander
    Jan 20 at 16:52

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