Balance the following redox reaction in acidic solution: H3PO4 + HNO2--> N2O4 + H3PO3

Answer 1

I'll help. P goes from +5 oxidation state on the left to +3 on the right. N goes from + 3 on the left to +4 (for each)N on the right. To make it easier to balance, I would start by multiplying HNO2 by 2 so the equation will read
H3PO4 + 2HNO2 ==> N2O4 + H3PO3
To make H balance add H2O to the appropriate side.