A litre of air contains 9.2 x 10^-4 mol of argon. Taking the molar mass of argon as 39.95 g/mol, what mass of argon is this?

1. To get a mass from an amount, multiply the moles by the molar mass. 2. That gives 9.2 x 10^-4 mol x 39.95 g/mol. 3. The product is 0.037 g of argon. 4. Units cancel correctly, since mol multiplied by g/mol leaves grams. 5. As a check, about one thousandth of a mole should weigh about one thousandth of 40 g, near 0.04 g. _Source: OpenStax Chemistry (CC BY 4.0), Ch 3 "Composition of Substances and Solutions", section 3.1 Formula Mass and the Mole Concept_