Question

Redox equations.. Please help explain so I can fully understand it....?

Identify the elements that undergo changes in oxidation number in the reactions:

•NaI(aq)+3HOCl(aq)→NaIO3(aq)+3HCl(aq)
Answer:
•I,Cl
___________
3SO2(g)+2HNO3(aq)+2H2O(l)→3H2SO4(aq)+
2NO(g)
Answer:S,N
________
•2H2SO4(aq)+2NaBr(s)→Br2(l)+SO2(g)+
Na2SO4(aq)+2H2O(l)
Answer:S,Br

For all of them, I would guess one element correctly but not the other... Could someone please explain how to get these answers? Thanks.

Answer 1

the oxidation numbers are just the charges of each ion in each compound. The total charge of a compound must always be zero, so each of the charges must balance. For the first reaction, NaI has charges of (+1)(-1), for a net charge of zero.

The HOCl can be found the same way: the (OH) is a -1, which means the Cl is a +1, otherwise it wouldn't balance.

As a product, the Cl has changed to partner with H+, making the Cl a -1. The iodine is changed the same way. Find the total charge of the molecule or ion, then find the individual charges of the pieces to see which atoms have changed their oxidation states.