Question

Calculate the pH of a buffer solution prepared by mixing 200 mL of 0.10 M NaF and 100 mL of 0.050 M HF.

Answer 1

Answer:

$pH=3.74$

Explanation:

Hello,

In this case, by using the Henderson-Hasselbach equation one could compute the pH considering that the pKa of hydrofluoric acid, HF, is 3.14:

$pH=pKa+log(\frac{[base]}{[acid]} )$

Whereas the concentration of the base and acid are computed by considering the mixing process with a total volume of 300 mL (0.3 L):

$n_{HF}=0.1L*0.05mol/L=0.005molHF\\\\n_{NaF}=0.2L*0.1mol/L=0.02molNaF$

$[HF]=\frac{0.005molHF}{0.3L}=0.017M$

$[NaF]=\frac{0.02molHF}{0.3L}=0.067M$

Therefore, the pH turns out:

$pH=3.14+log(\frac{0.067M}{0.017M} )\\\\pH=3.74$

Regards.