# RedOx Electron Balancing question

#### todaparty

10+ Year Member
Hey all, sorry for the hmwk question but I just had a quick Q...its late so maybe I'm missing something....

Balance the RedOx Rxn: As2O3 + NO3- ---> H3AsO4 + N2O3

1/2 reactions:

4e- + AS2O3 + 5H20 ---> 2H3AsO4 + 4H+

and

2NO3- + 3H+ ---> N2O3 + 3H2O + 1e-

So here's my question: Can I multiply the 2nd 1/2 rxn by 4 and the top by 1? Cuz when I do that and cancel out, the Hydrogens don't balance out...

(4e- + AS2O3 + 5H20 ---> 2H3AsO4 + 4H+) x 1
(2NO3- + 3H+ ---> N2O3 + 3H2O + 1e-) x 4

4e- + AS2O3 + 5H20 ---> 2H3AsO4 + 4H+
8NO3- + 12H+ ----> 4N2O3 + 12H20 + 4e-

cancel out

8NO3- + AS2O3 + 8H+ ----> 4N2O3 + 2H3AsO4 + 7H20

8 H on the left, 20 on the right??

##### Pharmacy Student
10+ Year Member
7+ Year Member
Hey all, sorry for the hmwk question but I just had a quick Q...its late so maybe I'm missing something....

Balance the RedOx Rxn: As2O3 + NO3- ---> H3AsO4 + N2O3

1/2 reactions:

4e- + AS2O3 + 5H20 ---> 2H3AsO4 + 4H+

and

2NO3- + 3H+ ---> N2O3 + 3H2O + 1e-

So here's my question: Can I multiply the 2nd 1/2 rxn by 4 and the top by 1? Cuz when I do that and cancel out, the Hydrogens don't balance out...

(4e- + AS2O3 + 5H20 ---> 2H3AsO4 + 4H+) x 1
(2NO3- + 3H+ ---> N2O3 + 3H2O + 1e-) x 4

4e- + AS2O3 + 5H20 ---> 2H3AsO4 + 4H+
8NO3- + 12H+ ----> 4N2O3 + 12H20 + 4e-

cancel out

8NO3- + AS2O3 + 8H+ ----> 4N2O3 + 2H3AsO4 + 7H20

8 H on the left, 20 on the right??

Your original second half-reaction (before multiplying by 4) doesn't have the H balanced.

#### todaparty

10+ Year Member
Your original second half-reaction (before multiplying by 4) doesn't have the H balanced.

yeah thanks , I just got to school and re-wrote the problem and I caught it.

I corrected it in case anyone cares.
Balance the RedOx Rxn: As2O3 + NO3- ---> H3AsO4 + N2O3

1/2 reactions:

4e- + AS2O3 + 5H20 ---> 2H3AsO4 + 4H+

and

2NO3- + 6H+ ---> N2O3 + 3H2O + 1e-

(AS2O3 + 5H20 ---> 2H3AsO4 + 4H+ + 4e-) x 1
(4e- + 2NO3- + 3H+ ---> N2O3 + 3H2O) x 1

AS2O3 + 5H20 ---> 2H3AsO4 + 4H+ + 4e-
4e- + 2NO3- + 6H+ ---> N2O3 + 3H2O

cancel out

2H+ + 2NO3- + AS2O3 + 2H20 ----> N2O3 + 2H3AsO4