The molar mass of iron (iii) oxide (fe2o3) is 159.7 g/mol. what is the correct way to write the molar mass of iron oxide as a conversion factor? startfraction 159.7 grams upper f e subscript 2 upper o subscript 3 over 159.7 moles upper f e subscript 2 upper o subscript 3 endfraction. startfraction 1 gram upper f e subscript 2 upper o subscript 3 over 159.7 moles upper f e subscript 2 upper o subscript 3 endfraction. startfraction 159.7 grams upper f e subscript 2 upper o subscript 3 over 1 mole upper f e subscript 2 upper o subscript 3 endfraction. startfraction 1 gram upper f e subscript 2 upper o subscript 3 over 1 mole upper f e subscript 2 upper o subscript 3 endfraction.