Answer to Question #300003 in General Chemistry for DTR

Question

Describe how to prepare 250 cm3 of sodium carbonate solution at a concentration of 0.5 mol dm-3 supplied Na2CO3, 10HO crystals.

Answer 1

For a 0.05 M (that's 0.05 mol/dm^3) Na2CO3 in 250 mL, how many mols Na2CO3 is that? That's mols = M x L = 0.05 M x 0.250 L = 0.0125 mols.

Then mols = grams/molar mass. You know mols and molar mass, solve for grams. To prepare such a solution, you add the grams Na2CO3 to an empty (and dry) 250 mL volumetric flask. Add about 100 mL distilled (or deionized) water, swirl until Na2CO3 is dissolved, then add water to the mark on the volumetric flask. Stopper, mix thoroughly, label. Done.