To create a 0.1 M carbonate buffer pH = 10.2. You choose to use a combination of HCO3- / CO32-. This buffer system has pKa = 9.9.

Question

 
a) Calculate how much you need to weigh in each of the sodium salts, NaHCO3 and Na2CO3, to create 1.0 L carbonate (with total concentration of carbonate of 0.1 M).
 
b) In the lab you have available a 0.25M hydrogen carbonate (HCO3 - solution) and a 0.50 M carbonate (CO32 - solution). Calculate the volume you need of each of these solutions to make 1.0 L carbonate buffer (0.1 M).