AQA AS Chem 1 HNO3 question

Hi

So I came across a question earlier on from Jan 11. It read this:

'Deduce an equation to show how NO2 reacts with water and oxygen to form nitric acid (HNO3).'

So it's going to be along the lines of: NO2 + H2O + O2 -> HNO3

I balanced this out to 2NO2 + H2O + 1/2O2 -> 2HNO3

The correct answer was 4NO3 + 2H2O + O2 -> 4HNO3 but the MS said accept/allow multiples.

I know you can use half O2s when balancing combustion reactions, but I was unsure as to whether I can do it here and if you can do it if you only have one O2.

Any help would be appreciated ^_^

Yes, your answer would get you the mark. According to my teacher, 'Multiples' also means factors so that's a perfectly valid response, one which I did myself.