Question

How many grams of dipotassium succinate trihydrate (K2C4H4O4·3H2O, MW = 248.32 g/mol) must be added to 530.0 mL of a 0.0398 M succinic acid solution to produce a pH of 5.908? Succinic acid has pKa values of 4.207 (pKa1) and 5.636 (pKa2).

Answer 1

Let us write succinic acids as H2Suc
The first ionization is
H2Suc ----> HSuc- +  H+
The seond ionization is
HSuc- ---->  Suc-2 + H+
Calculate the H+ concentration of from the first ionization using pKa1.
Then, calculate the H+ concentration from the second ionization using pKa2.
Next, use the buffer equation to calculate the concentration of the salt in the solution. Then, use the given volume to get the number of moles of the salt. Finally, use the given molecular weight to get the mass.