Question

how would adding acid to a buffer solution would change the value of ph?

Will the pH value increase or decrease?

what if we add base to a buffer solution? how would that change the value of pH of the buffer? increase or decrease ?

and could you please explain why?

Thanks!

Answer 1

A buffer is a solution that can resist pH change upon the addition of an acidic or basic components. It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable.

A buffer is able to resist pH change because the two components (conjugate acid and conjugate base) are both present in appreciable amounts at equilibrium and are able to neutralize small amounts of other acids and bases (in the form of H3O+ and OH-) when the are added to the solution.

There fore the ph would not change on adding acid.

Similarly on adding base also the ph would not change.

consider the simple example of a Hydrofluoric Acid (HF) and Sodium Fluoride (NaF) buffer. Hydrofluoric acid is a weak acid due to the strong attraction between the relatively small F- ion and solvated protons (H3O+), which does not allow it to dissociate completely in water.

HF(aq)+H2O(l)?F?(aq)+H3O+(aq)

  NaF(aq)+H2O(l)?Na+(aq)+F?(aq)

if base added

HF(aq)+OH?(aq)?F?(aq)+H2O(l)

In this reaction, the conjugate acid, HF, will neutralize added amounts of base, OH-, and the equilibrium will again shift to the right, slightly increasing the concentration of F- in the solution and decreasing the amount of HF slightly. Again, since most of the OH- is neutralized, little pH change will occur.

Similar thing happens when acid is added