Properties of Buffers Practice Test

The pH stays exactly the same because the buffer converts all added base into water with no change in buffer composition.

The pH changes little because $\mathrm{Na^+}$ consumes $\mathrm{OH^-}$ to form $\mathrm{NaOH(aq)}$, removing base from solution.

The added base is neutralized mainly by $\mathrm{CHO_2^-}$ forming $\mathrm{HCHO_2}$, so the pH decreases slightly.

The added base is neutralized mainly by $\mathrm{HCHO_2}$ forming $\mathrm{CHO_2^-}$ and water, so $\mathrm{[OH^-]}$ increases only slightly.

The pH changes little because $\mathrm{HCHO_2}$ is a strong acid that completely neutralizes any added base.