Question

i dont understand the relationship between stoicometry and the change in oxidation number
http://screencast.com/t/kenZyeozjX @Vincent-Lyon.Fr

Answer 1

can you please help me wid that @Vincent-Lyon.Fr

Answer 2

It the answer +2 ?

Answer 3

yes:) How can the professor go wrong ;)

Answer 4

Sulfur has an increase in oxydation number of +2

So stoichiometric amount of metallic must decrease by 2 to compensate.

Since there is twice as much metal reacting as sulfite, then the metallic element must be reduce by 1.

The half reaction will be :

\(Me^{3+}+1\,e^- \rightarrow Me^{2+}\)

Full equation will be :

\(2\,Me^{3+}+SO_3^{2-}+H_2O \rightarrow 2\,Me^{2+}+SO_4^{2-}+2H^+\)

Answer 5

got it thanks @Vincent-Lyon.Fr