[arjunsengupta]

  hi,
   
   a question came into my mind while i was studying with gibb's phase rule.suppose a  closed system
has solid mettalic gold and hydrogen iodide vapour.the later is undergoing adsorption on the former. in this situation what is the degrees of freedom of the system? itried to solve the question as folows-
    by gibb's phae rule   f=c-p+2.   
       in this case c=3   i took it 3 because the solid gold in the bulk,hydrogen iodide vapour and the surface gold atoms adsorbed with hydrogen iodide.
       p=3 too.   i, in this case,took under consideration the vapour phase, the solid bulk gold, and the surface gold atoms along with hydrogen iodide(adsorbed).
    in both the above cases i took surface gold atoms as different entity because langmuir's isotherm assumes during chemisorption a covalent bond is formed between adsorbate and adsorbent.
   all this gives  f=2.is my attempt correct? in either cases, what will be the physical interpretation of the fact?
         

[Mitch]

I woulf of thought c only equal 2

[arjunsengupta]

can u please explain a bit more? why would i not consider surface gold atoms as a different component,while they form different covalent bonds?

[Mitch]

Is it covalent bonding?

[arjunsengupta]

probably chemisorption provides a monolayer of adsorbed substance, that is bound through covalent bonding.am i incorrect,if yes,please confirm.