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Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: AlbertoA on October 10, 2011, 06:56:29 PM

Title: Arsenic-Sulphur affinity
Post by: AlbertoA on October 10, 2011, 06:56:29 PM

which As has more affinity for the H2S? the As(III)or the As(V)
and why?
I read that As(III) has more affinity, but I don't see any explanation of that behaviour
perhaps As (III) is a soft lewis acid and H2S a soft base?

Title: Re: Arsenic-Sulphur affinity
Post by: Yakimikku on October 12, 2011, 06:26:59 PM

I think you have it. As(V) is definitely harder than As(III) because of the increase in oxidation state. H₂S, being as soft base would likely prefer binding to As(III) for that reason. Other than confirming your reasoning, I don't specifically know much about As.

Title: Re: Arsenic-Sulphur affinity
Post by: Wald_ron on October 13, 2011, 10:18:14 AM

As(III) has a lower charge density than As(V) which means that As(V) is harder. As(III) is therefore softer than As(V) and H2S is a soft base. Soft prefers Soft. Thus As(III) has more affinity for H2S.