A 50.00ml sample of 0.200M hydroflouric acid (HF) is titrated with 0.200M NaOH. The Pka of HF is 3.452. a) calculate the pH of the HF solution before titration b) calculate the pH after the addition of 20.00ml of NaOH

Answer 1

The pH at the beginning of the titration is just the pH of a 0.2 M HF solution.

b).
moles HF = M x L = ??
moles NaOH = M x L = ??
Which is in excess. Subtract. If HF in in excess, you will have a buffer solution of HF and NaF. If NaOH is in excess the pH will be determined by the concn OH.
Post your work if you get stuck.

Answer 2

for a) i got the pH of HF to be 2.07 and for b) i'm a little stuck.
the mole of HF is 0.2M x 0.05L =0.1mol
the mole of NaOH is 0.2M x 0.02 L= 0.02mols. this is where i'm stuck

Answer 3

Hint write a balnace equation between HF and NaOH.