Chemistry
posted by Karie on .
Calculate the pH of the following buffer solutions:
a) a solution made by dissolving 2.733g KH2PO4 and 4.508g K2HPO4 in water to give 250 ml of solution.
b)a solution made by mixing 35.00 ml 0.24 M C6H5NH2 with 15.00 ml 0.19 M C6H5NH3CL. The base dissociation constant Kb is 4.00 X 10^10 for C6H5NH2. Assume that the final volume is the sume of the volumes of the two solutions that are mixed.

Use the HendersonHasselbalch equation. If you get stuck explain what it is you don't understand.

I don't understand where to start. Do i turn the grams given in part a) to moles first? then i am not sure what to do

Yes, convert g to moles. Look up the Ka value for the acid and convert that to pKa, then plug into the HH and calculate pH.

how would you do part b?

you have 20 ml of 0.1 M aqueous solution of the weak base (CH3)N (Kb = 7.4 x 10^5). This solution will be titrated with 0.1 M HCl.
how many ml of acid must be added to reach the equivalence point? 
a) 7.432