(a(i))[3]
In the part enclosed on the graph, identify the two organic species that are present in the solution. Explain why the pH of the mixture changes only slowly and steadily in this region as sodium hydroxide is added.
(a(ii))[1]
The equivalence point in this acid-base titration is reached when the two solutions have been combined in exactly equal molar proportion.\n\nSuggest why the pH is greater than $7$ at the equivalence point in this titration.
(b)[3]
Calculate 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. [$M_r\!: \text{NH}_4\text{VO}_3 = 116.9$]