I am prepping a buffer solution of 1M acetic acid and 1M calcium acetate with a pH of 5, but it has been a long time since chem 101. I have some notes from an old lab mate that suggested that 600mL of acetic acid and 150mL Ca-acetate (with water added to make 1L) makes about a pH of 4.5. However when try using Henderson-Hasselbalch to get amount for a pH of 5 I get vastly different results - 640mL Ca-acetate and 360 mL of acetic acid. Where am I going wrong? Any tips on how to calculate the amounts needed correctly?