What mass of sodium oxalate na2c2o4 is needed to prepare 0.250 l of a 0.100 m solution?

Molarity = number of moles of solute / liters of solution

number of moles = molarity * liters of solution

number of moles of Na2C2O4 = 0.1 * 0.25 = 0.025 moles

Now, from the periodic table:

mass of Na = 22.9 grams

mass of C = 12 grams

mass of O = 16 grams

molar mass of Na2C2O4 = 2 (22.9) + 2 (12) + 4 (16) = 133.8 grams

Therefore, one mole is equal to 133.8 grams. To know the mass of 0.025 moles, all you have to do is cross multiplication as follows:

mass = (0.025*133.8) / 1 = 3.345 grams