Question

A buffer solution is prepared by mixing 66.3 mL of 0.0409 M sodium dihydrogen phosphate with 90.1 mL of 0.855 M sodium hydrogen phosphate.

A table of pKa values can be found here. http://chemresources.chemistry.dal.ca/firstyear/acid_base.html



1. Calculate the pH (to two decimal places) of this solution.



Assume the 5% approximation is valid and that the volumes are additive.

2. Calculate the pH (to two decimal places) of the buffer solution after the addition of 0.361 g of sodium hydrogen phosphate (Na₂HPO₄) to the buffer solution above.



Assume 5% approximation is valid and that the volume of solution does not change.