What mass of oxalic acid dihydrate, H2C2O4•2H2O, is needed to make a 0.357 M solution of oxalic acid in a 250.0mL volumetric flask?

Molarity is expressed as the number of moles of solute per volume of the solution. The mass of oxalic acid dihydrate needed for the solution is calculated as follows:

Amount in moles: (0.357 mol H2C2O4•2H2O / L) (.250 L) = 0.0893 mol H2C2O4•2H2O

Amount in mass : 0.0893 mol H2C2O4•2H2O (126.08 g / mol) = 11.2589 g H2C2O4•2H2O

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