(a(i))[3]
Within the part of the graph that is circled, identify the two organic species in the solution. Explain why the pH of the mixture rises only slowly and steadily in this region as sodium hydroxide is added.
(a(ii))[1]
At the equivalence point in this acid-base titration, the two solutions have been combined in exactly equal molar amounts. Suggest why the pH is greater than $7$ at the equivalence point in this titration.
(b)[3]
Determine the percentage by mass of $\text{NH}_4\text{VO}_3$ in the $0.150\,\text{g}$ impure sample of $\text{NH}_4\text{VO}_3$. Give your answer to three significant figures. [$M_r: \text{NH}_4\text{VO}_3 = 116.9$]