1. The problem statement, all variables and given/known data What is the pH of a carbonate buffer solution prepared by mixing 1.500 mol Na2CO3 and 1.000 mol NaHCO3 and adding water to make a 1.000 L solution? (pKa of (HCO3)- is 10.32) A 200.00 mL sample of 1.000 M nitric acid was added to the buffered solution above. What is the resulting pH? 2. Relevant equations Henderson-Hasselbalch equation (pH = pKa + log ([A-]/[HA])) pH = -log [H+] 3. The attempt at a solution I used the equation for the first part, and I calculated a pH of 10.50 (pH = 10.32 + log (1.500/1.000)). Is this correct? I'm not sure how to include the second part though... I'm guessing I'm supposed to calculate the resulting pH when nitric acid is added to 1.000 L of water and then somehow use that pH for the second part... If that makes any sense. Any help is appreciated!