mark scheme a level chemistry chem june marking guidance mark comments h c o mn h o co mno mn or mn possible because mn can exist in variable oxidation states ea lowered because oppositely charged ions attract mn reduced to mn by c o mn oxidised back to mn by mno equation equation if catalyst incorrect can only score m and m these marks can be gained in any order m may appear before m m and m can be scored in unbalanced equations or in words showing mn c o mn mno mn mn of question a b graph marks s shaped curve must not rise significantly and must not fall rapidly initially starts on concentration axis and is levelling out can level out on time axis or above but parallel to time axis explanation marks slope rate increases as catalyst concentration forms slope rate decreases as concentration of mno decreases or reactants are being used up ions reactant s mark scheme a level chemistry chem june cannot score graph marks m and m if no axes and or no labels explanation marks can be awarded independent of graph of