Find L HNO2 and NaNO2?

Question

what volumes of 0.58M HNO2 and 0.59 NaNO2 must be mixed to prepare 1.00 L of solution buffered at pH=3.46

i am still looking for help because i am not sure if my own answer is correct.

Answer 1

We can use the Hendersson - Hasselbach equation:

pH = pKa + log [Acid] / [Base]

knowing that pKa (nitrous acid) = 3.34

we get the ratio:

[Acid] / [Base] = 10^(3.46 - 3.34) = 1.318

According to this result, concentration of acid (HNO2) is 1.318 times the concentration of base (NO2-) in buffer solution.

It means that: V (Acid) = 1.318 V(Base)

also, V(acid) + V(base) = 1 L then:

We solve the system and we get:

V(acid) = 0.56 L
V(base) = 0.44 L

(Note: As you can see I assume that both concentrations of solutions are almost the same)

That is what I remember from my courses a long time ago.

Hope you received another opinions to verify the results.

Good luck!