Tricky, but doable. I have converted it ifrst to
Na
2O + Na
2S + SO
2 -> Na
2S
2O
3(CO
2 can be always added on both sides) but it didn't help much.
Then I realized it is almost balanced - the only problem is, there is too much sodium on the left. Playing with Na
2O and SO
2 I will always need more sulfur (two atoms per thiosulfate). So I decided to try 2Na
2S and the rest was a breeze. But that's more luck than a systematic approach.
Systematic approach will be to use
algebraic method.
And yes, my EBAS balances this equation in no time.