[chimai]

I thought I understood the question, but when I tried to work it out, I think I confused myself. So, the questions are:

Given:
pKa = 6.86
prescribed pH = 6.4

(i) Calculate how much potassium di-hydrogen phosphate (KH2PO4, which hs a molecular weight of 136.2g/mol) you need to make 250mL or a 25mM buffer, and how much you would need to make a 100mM buffer.
(ii) Calculate how much 1 N KOH you need to add to e4ach quantity of KH2PO4 in order to produce a buffer of the correct pH.

Any help would be awesome. Thank you.

[AWK]

Read rorum rules. Show some work. Borek primer (http://www.chembuddy.com/?left=lectures) is a good starting point!