Question

In Activity 1, what happened to the pH of the water sample as 0.1 M HCl was added? How did this compare to what happened with addition of one drop of 0.1 M HCl to each buffer solution? In Activity 1, why did the pH of the buffer solutions change after the addition of 10 drops of 0.1 M NaOH? NaOH is strong base when its added to the solution, its react with the weak acid, so that cause the PH of the buffer solution change. In Activity 2, which concentration was the effective buffer? Explain what happened chemically as the buffer became more dilute.

please solve the hilighted Questions

Answer 1

Answer 1. Addition of strong acid raises the pH of the water. HCl + H₂O → H₃O⁺ + Cl^- is a basic reaction to understand the release of H⁺ ions. The proton (H⁺) from the acid binds to neutral water molecules to form H₃O⁺ raising the concentration of H⁺ making solution more acidic.

First we need to understand what does buffer constitute of. If we mix a weak acid (HA) with its conjugate base (A^-), both the acid and base components remain present in the solution. This is because they do not undergo any reactions. When HCl was added to the buffer, the weak base will react with the H⁺ from the strong acid to form the weak acid HA: H⁺ + A^- → HA. The H⁺ gets absorbed by the A^- instead of reacting with water to form H₃O⁺(H⁺), so the pH changes only slightly.

Answer 3. Even though you dilute the buffer, the concentration of H⁺ does not become smaller, because the acid in a buffer progressively dissociates to keep it (almost) identical. This is an effect of the acid/base equilibrium.