F.4 chem (somebody Plz help)

2008-08-09 2:52 am

3Cl2(g) +6KOH(aq)→5KCl(aq)+ KCl3(aq)+3H2O(l)
Here KOH provides a medium for the disproportion of chloride. Cl acts as both oxidizing and reducing agent.

Question: Is that only when Cl2 gas react with KOH, Cl will act as both oxidizing and reducing agent or just any hydroxide will do? Can anyone tell me something from this equation.( anything you know is ok)

When sodium hydroxide is added to iron(II) sulphate ,the reaction is
A green precipitate deposits
Fe2+ + 2OH-→Fe(OH)2
Originally I think the equation should be Fe2+ being both the oxidizing and reducing agent as OH present . But it is wrong .

So my question is how can I know when will a substance act as both the oxidizing and reducing agent?THZ

回答 (1)

cheungwaito

2008-08-11 4:45 am

✔ 最佳答案

in fact many species can disproportionate. for example,

2Cu ----->Cu2 Cu

normally, you need to consider the oxidation of a species. inreaction of chlorine with hydroxide, the oxidation state of chlorine changes from 0 to -1 and 0 to 5(KClO3) . if such change of oxidation state is allowed, then the species will
undergo such change. also, in change of oxidation state, redox is involved.

Fe2 2OH-→Fe(OH)2 is merely electronstatic attraction. no redox is involved, moreover, Fe does not exist, OH- does not undergo reduction.

Halogens undergo disproportionation in hydroxide soultion, the one you write is a 2 step equation,

3Cl2 2OH-→Cl- ClO- H2O
3ClO-→ 2Cl- ClO3 1- (it is singly charged)

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