Calculate the ratio of naf to hf required to create a buffer with ph = 4.05.

PH is the test of acidity or basicity of a solution. it follows the formula:

pH = pKa + log [salt] / [acid] where NaF is the salt and HF is the acid in this case.

By literature, Ka of HF is 3.5*10^-4

pKa = - log (Ka) = 3.46

pH = pKa + log [NaF / [HF]

4.05 = 3.46 + log [NaF / [HF]

log [NaF / [HF] = 0.59

[NaF / [HF] = 3.89