You should use k1. You are starting with NaHCO3, not Na2CO3. And (base) + (acid) = 0.5M
For buffers you want to use a pKa within +/- 1 of the desired pH.
How would you make 100 mL of a carbonic acid buffer at 0.5 M and pH = 6.0 using 1.0 M NaHCO3 and either 1.0 M NaOH or 1.0 M HCl and water?
so far, I have 50 mL NaHCO3. I plugged that into the Henderson-Hasselbalch equation of pH=pKa + log [A-]/HA] and knowing that [Buffer]= [A-] + [HA] , and get [HA] = 0.5 M. Meaning that [A-] is zero... And that doesn't sound right. I'm thinking I used the wrong pKa value? I have the equation for the dissociation of H2CO3 with the pKa being 6.35, and the equation of HCO3 dissociating with a pKa of 10.33. I would think I would use 10.33 since I am starting with NaCO3, but clearly I'm messing up somewhere. Anything would help me at this point!! Thanks in advance for your time.
1 answer
5 answers