n-factor of dichromate is 6 .Also, the n-factor of Mohr's salt is 1 as :FeSO4​(NH4​)2​SO4​⋅6H2​O⟶O.A​Fe3+Mohr's salt∵1 mole of dichromate =6 equivalent of dichromate.∴6 equivalent of Mohr's salt would be required.Since, the n-factor of Mohr's salt is 1, 6 equivalent of it would also be equal to 6 moles.Hence, 1 mole of dichromate will oxidize 6 moles of Mohr's salt.