Question

Address the following and Explain:

a) what happens when a strong base is added to a solution that only has significant amounts of a weak base

b) what happens when a strong base is added to a solution initially made up of significant amounts of a weak base and its conjugate acid

Answer 1

In case a), In the presence of weak base if srong base is added, then the resulting will become more basic as number of OH^- ions increases significantly. Thus, resulting in significant increase in pH.

In case b), solution weak base and its conjugate acid is known as buffer solution. On addition of strong base, this buffer solution consume excess of OH^- ions and prevent the increase in pH of solution. For example lets say, weak base NH3 and its conjuagte acid NH₄⁺ ions is present as buffer solution. If we add strong base NaOH to the buffer solution, the generated OH^- ion from strong base will be consumed by NH₄⁺ and gives NH₃ and H₂O. In the whole process only NH3 is being produces which ia weak base and do not contribute to significant increase in pH. Thus, buffer solutions inhibits the rise in pH by capturing excess of OH^- ions.