50.50 mL of 0.116 M HF is titrated with 0.1200 M NaOH. What is the pH when 25.00 mL of the base have been added. (Ka = 6.8 x 10-4)
50.50 mL of 0.116 M HF is titrated with 0.1200 M NaOH. What is the pH when 25.00 mL of the base have been added. (Ka = 6.8 x 10-4)
HF + NaOH ----------------------> NaF + H2O
50.5 x 0.116 0.12 x 25 0 0
5.86 3 0 0 --------------initial millimoles
2.86 0 3 3 ----------------at equilibrium
the mixture contain NaF salt + HF acid so it is buffer
For acidic buffer
pKa = -log Ka = -log(6.8 x 10-4) = 3.167
pH = pKa + log[salt/acid]
pH = 3.167 + log[ 3 / 2.86]
pH= 3.19
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