redox calculation

http://www.ocr.org.uk/Images/319513-question-paper-unit-f325-01-equilibria-energetics-and-elements.pdf

For Q7 b in this paper, I had worked out CrO4- ( which has the ratio of 4 in the first equation )to be 0.034. I was thinking that since you have 2 moles of Cr in 2Fe(CrO2)2 anyway , so you would end up with 0.034 moles of Cr at the end. Is this the right way to think about this. In the mark scheme it states that FeCrO4 is chosen instead as this is what reacts with I- so I am not sure.

Thanks

You are not being very clear.

If you start off with x mol of Cr you must end up with x mol of Cr

So the question says 2Fe(CrO2)2 contains chromium but this reacts with Na2O2 to form Na2CrO4 which also contains chromium ions. I have got to the stage where I found 4Na2CrO4 = 0.034 mol. My question is wouldn't the moles of chromium ions be the same in both 2Fe(CrO2)2 and 4Na2CrO4 since you have 2 moles of chromium ions in 2Fe(CrO2)2 but only 1 moles of chromium ions in Na2CrO4. So surely no matter which compound you consider the moles of chromium ions will be the same in both 2Fe(CrO2)2 and Na2CrO4. Is this right ?