Can someone explain why for the equilibrium its 2-2x in the marking scheme but yet in the examit solutions its 2-x which makes more sense to me? Where is the 2-2x coming from??
Because it's 2NO, but only 1N2 and 1O2, the change in NO is going to be double the change of the other two molecules. If you made the change in NO 'x' then you'd be dealing with 0.5x and it'd be a bit messier. Either is fine, as long as your ratios are right.