A 55 kg woman has 7.5 x 10^-3 mol of hemoglobin, molar mass 64,456 g/mol, in her blood. What mass of hemoglobin is that?

1. Mass equals moles multiplied by molar mass. 2. Substituting gives 7.5 x 10^-3 mol x 64,456 g/mol. 3. The product is 483 g of hemoglobin. 4. Sanity check: about a hundredth of a mole of a 64 kg per mole protein should weigh several hundred grams. 5. The value 64.5 g multiplies the molar mass by a bare 10^-3 and forgets the factor of 7.5. _Source: OpenStax Chemistry (CC BY 4.0), Ch 3 "Composition of Substances and Solutions", section 3.1 Formula Mass and the Mole Concept_