Did I Prepare My Phosphate Buffer Solution Correctly?

[brendw2005]

Hi everybody!
I want to prepare 1000 ml of 0.1M phosphate buffer solution, pH = 7.0. I used Henderson Hasselbach's equation: pH = pka + log [salt]/[acid]. I obtained 0.062 moles of H2PO4- and 0.038 moles of HPO42-. Where I am wrong? Thanks a lot!
B

 

[chemisttree]

Show your work. Which pKa did you use? What species did you use for [salt] and [acid]?

 

[brendw2005]

Thanks for replying!

I used (H2PO4)- ↔H+ + (HPO4)2-
Ka for this equation is 6.2*10-8, deci pKa = 7.21.
Salt = (HPO4)2-
Acid = (H2PO4)-

 

[chemisttree]

I get the same...

 

[brendw2005]

So, I did it right! Thanks!