Answer to Question #153946 in General Chemistry for rob

Question

I2 (aq) + I- (aq) → I3- (aq)      

 

 what element is oxidized? What element is reduced? Justify using oxidation numbers.

Answer 1

Since iodine is the only element present in the equation, obviously iodine is oxidized and iodine is reduced. The overall oxidation number of I₃^- ion is -1, so each iodine formally has the oxidation state of -1/3. It means that I₂ is reduced as it changes its oxidation state from 0 to -1/3, while I^- is oxidized as it changes its oxidation number from -1 to -1/3.