A 0.500 L vinegar solution contains 25.2 g of acetic acid, molar mass 60.052 g/mol. What is its molarity?

1. Molarity needs moles of solute, but the mass is given, so convert first. 2. Amount of acetic acid = 25.2 g / 60.052 g/mol = 0.4196 mol. 3. Now divide by the solution volume: 0.4196 mol / 0.500 L. 4. The concentration is 0.839 M. 5. Units check out, since moles divided by litres gives mol/L, which is M. 6. The value 0.420 M stops at the mole count and forgets that only half a litre is present. 7. The value 1.68 M multiplies by 0.500 L instead of dividing by it. _Source: OpenStax Chemistry (CC BY 4.0), Ch 3 "Composition of Substances and Solutions", section 3.3 Molarity_