A sample of 2.561 mol of gold has a mass of 504.4 g. What is the molar mass of gold to three significant figures?

1. Mass equals moles multiplied by molar mass, so molar mass equals mass divided by moles. 2. Substituting gives 504.4 g / 2.561 mol. 3. The division yields 196.95 g/mol, which is 197 g/mol to three significant figures. 4. Units check out, since grams divided by moles gives grams per mole. 5. The value 504 g/mol simply repeats the sample mass and ignores that there are more than two moles present. 6. The value 394 g/mol is twice the correct answer, the result of halving the mole count first. _Source: OpenStax Chemistry (CC BY 4.0), Ch 3 "Composition of Substances and Solutions", section 3.1 Formula Mass and the Mole Concept_