Ammonia - Ammonium Chloride Buffer Systems

Question

Can the NH₃/NH₄Cl system be used to prepare a buffer of a pH 9.5? Why or why not? Yes, but I am not sure why.

Can the NH₃/NH₄Cl system be used to prepare a buffer of a pH 5.0? Why or why not? No but I am not sure why.

What makes a good buffer?

Answer 1

A buffer is generally useful over a pH range of ± 1 pH units of the pKa . The pKa for NH3/NH4+ is 9.3 so a buffer in the pH range of 8.3 to 10.3 should be ok.

No, same explanation as above.

A good buffer (not Good buffer) is one that resists changes in pH when an acid or base is added. This occurs when the ratio of weak acid or weak base to the conjugate base or acid is 1:1.

(note: There are Good buffers, named after a chap named Good, but that isn't what the question is about).