Titration of 50.0mL of 0.130mol/L sulfurous acid with 0.14mol/L sodium hydroxide.
What would be the buffer region on the graph?
To determine the buffer region on the graph, we need to consider the pH range at which the solution acts as a buffer.
A buffer solution resists changes in pH when small amounts of acid or base are added. It consists of a weak acid (HA) and its conjugate base (A-), or a weak base (B) and its conjugate acid (BH+).
In this case, sulfurous acid (H2SO3) is a weak acid. Its conjugate base is sulfite ion (HSO3-). Sodium hydroxide (NaOH) is a strong base.
During the titration, initially, we have mostly sulfurous acid in solution, which acts as the weak acid in the buffer solution. As sodium hydroxide is added to the solution, it reacts with sulfurous acid to form sodium sulfite and water:
H2SO3 + 2NaOH → Na2SO3 + 2H2O
As the reaction progresses, the concentration of sulfurous acid decreases, and the concentration of sulfite ion increases. This gradual shift in the concentrations of weak acid and its conjugate base characterizes the buffer region.
The buffer region typically occurs around the equivalence point in a titration curve, where the acid and base are mixed in stoichiometric proportions. In this case, the equivalence point is reached when the moles of sulfurous acid reacting with sodium hydroxide are equal.
To determine the exact buffer region, we would need to calculate the volume of sodium hydroxide required to reach the equivalence point using stoichiometry.