[SOLVED] Chemistry Problem The question is Calculate the mass of pure Na2CO3 needed for the preparation of 250.00mL of a 0.005M standard carbonate solution. when it says PURE Na2CO3, what molarity does it mean? is it 1M?? my guess is to use M1V1 = M2V2 to solve my final volume is 250mL final concentration is 0.005 M and if the pure Na2CO3 means 1M then that would be what i would be using as my stock right? then i would solve for the volume of that stock i need. After that I would use the density of Na2CO3 to find the mass is that right?