You are asked to prepare a ph = 3.00 buffer solution starting from 1.25 l of a 1.00m solution of hydrofluoric acid (hf) and an excess of sodium fluoride (naf).
what is the ph of the hydrofluoric acid solution prior to adding sodium fluoride?
how many grams of sodium fluoride should be added to prepare the buffer solution? neglect the small volume change that occurs when the sodium fluoride is added.

a. pH=1.59

Hydrofluoric acid is a weak acid, meaning it would not entirely dissociate. The capacity of dissociation of the compound will be given by it's acid dissociation constant ().

We know that the pH is , therefore using the dissociation constant, we can find the concentration of H+.

HF⇄

For this acid

Let's assume x is the unknown amount of the products, and the initial concentration, in this case 1.00M -x is the final amount of the reagent.

Therefore,

Neglecting the x in the numerator, given that the effect over the 1.00 M will be little we obtain that

b. grams NaF=34.65 g

Given the desired pH, and the initial concentration of {HF]=1.25L*1.00M=1.25 mol, we can use

the positions which points up in upward carbon and down in downward carbon are axial

and vice versa holds true for equatorial positions

so the correct answer with labelled diagram will be