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

`pH=3.74`

Step-by-step 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(([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]=(0.005molHF)/(0.3L)=0.017M`

`[NaF]=(0.02molHF)/(0.3L)=0.067M`

Therefore, the pH turns out:

`pH=3.14+log((0.067M)/(0.017M) )\\\\pH=3.74`

Regards.