A2 chemistry - how do i know there's an OH in the products?

[1832vin]

This is the question and the answer, the problem is i don't know how to get to the answer
top is question and bottom is answer

I attempted to divide the gas concentration by 24 to get molar mass, but that didn't work
and how am i suppose to know that OH- is one of the products? i guessed that there is fe(OH)3, but that's all i got right...

it's the very last question from this A level paper

please help, my exams are close, and i have no clue at all...

 

[Borek]

I attempted to divide the gas concentration by 24 to get molar mass

I see no concentration in the question.

And why do you divide? You have mass of 1 mL, right? Assuming there is one mole of a gas at RTP, what volume does it occupy? What is its mass (given the density as listed)?

It is not that there is OH^- between products, however, you won't be able to balance the reaction without either H⁺ of OH^-. That's a quite common situation when it comes to redox reactions in water.

 

[epenguin]

1.3333 × 22 = very close to 32 so that part works well.