Salt Dissolution Problems [ENDORSED]

[Andrew Wang 1K]

For most salt dissolution (buffer solution) problems one of the ions will have no impact on the pH. How do you solve cases where both dissolved ions, from a salt like ammonium floride, impact pH?

[Chem_Mod]

We don't make buffers using a different weak acid and weak base.

In your salt, ammonium fluoride, it would be formed from the weak base NH₃, and the weak acid HF.

Solving for the pH with a salt like that is complicated as one has to set up two equilibria, one for the weak base and another for the weak acid.
Not suitable for general chemistry. :-)

Same reason why titrations are not done with a weak acid and weak base.

Titrations are always:

Strong acid and strong base.
Or
Strong acid and weak base.
Or
Weak acid and strong base.

If one does not know if the sample is a strong acid/base, then always use a titrant that is a strong acid or strong base.

Nice question Andrew.