Chemistry Forum

The following Latimer diagram is known for the metal M in acid solution.

MO₃ (s) -> MO₂ (s) -> M₃+ (aq) -> M₂+ (aq) -> M(s)
-------(+0,50 V)----(+0,40 V)------(-0,20 V)-----(-0,05V)

-Indicate with an explanation and response form, which of the compound (s) or ions (s) mentioned in above Latimer diagram that can be disproportionate.

The rule is that: if the potential to the right of the species is higher than the potential on the left, it will disproportionate.

But as I can see, no compounds or ions are disproportionate. Is that true ?

Many elements and their oxides or acid forms can disproportionate, and these processes even happen in the environment. Sulfur is a good example http://www.iapws.jp/Proceedings/Symposium05/365Lin.pdf

Another example of sulfur disproportioning is the following reaction of sodium dithionite (or hydrosulfite) in water or in the presence of acid http://www.inchem.org/documents/sids/sids/7775146.pdf
2 Na₂S₂O₄ + H₂O → 2 NaHSO₃ + Na₂S₂O₃
In acidic medium: 2 H₂S₂O₄ → 3 SO₂ + S + 2 H₂O
In strongly acidic medium: 3 H₂S₂O₄ → 5 SO₂ + H₂S + 2 H₂O


or similar for sodium thiosulfate
Na₂S₂O₃ + 2 HCl = H₂O + 2 NaCl + S + SO₂

Elementary phosphorous (usually white) and phosphorous (3+) compounds disproportionate too.
http://www.arkat-usa.org/get-file/19305/

P₄ + NaOH = PH₃ + NaH₂PO₂
http://it.answers.yahoo.com/question/in ... 838AA₃gVLm


Keep looking on your own. You’ll find plenty other examples.