• A?disproportionation?reaction is where one element in a chemical is simultaneously reduced and oxidised, e.g.

2Cu+?(aq) → Cu2+?(aq) + Cu (s)

• Standard electrode potentials can be used to explain disproportionation reactions

1. • 1. Cu2+?(aq) + e–?? Cu+?(aq)Eθ?= +0.15 V
     2. Cu+?(aq) + e–?? Cu (s)Eθ?= +0.52 V
   • The electrode potential value for equation 1 is more negative, therefore, this reaction will be the oxidation reaction and proceed to the left
   • The electrode potential value for equation 2 is more positive, therefore, this reaction will be the reduction reaction and proceed to the right
     • You now have:

Cu+?(aq) ? Cu2+?(aq) + e–

Cu+?(aq) + e–?? Cu (s)

• • • Combining these two equations agrees that the overall equation is possible

2Cu+?(aq) → Cu2+?(aq) + Cu (s)