Buffer chemistry question

Question

1 question.A 100.0-mL sample of 1.00 M HCl is titrated with 1.00 M NaOH. What is the pH of the solution after 100.0 mL of NaOH have been added to the acid?

second questioin

The Ka of hypochlorous acid, HClO, is 3.5 x 10-8. What [ClO-]/[HClO] ratio is necessary to make a buffer with a pH of 7.71

Answer 1

1.  100 ml ( 1m ) = 100 mole of H+

100mL ( 1 M ) = 100 mmoles OH-  the two react to form 100 mmoles of NaCl + water. As NaCl is the conjugate base of the astrong acid HCl it is a weak base and will NOT hydrolyze.The pH is that of pure water = 7.0

2.  The Ka is 3.5 X 10^-8 so the pKa = -log ( 3.5 X 10^-8 ) = 7.46

so using the Hendersen/Haselbach

pH = pKa + log [baseform]/[acidform]  

7.71 = 7.46 + log base/acid  so log of the base/acid ratio = 0.25

taking the antilog   the ratio is 1.778 = 1.78:1