(a)[1]
A student prepares an aqueous solution of potassium nitrate. She adds dilute nitric acid to an aqueous solution of a salt. State a salt that she could use.
(b)[1]
The student measures the mass of potassium nitrate that dissolves in $100\text{ cm}^3$ of water at various temperatures. On the grid, continue the graph to $0^{\circ}\text{C}$.
(c)[1]
Using the graph, find the temperature at which the solubility is $180\text{ g}/100\text{ cm}^3$.
(d(i))[1]
Using the graph, find the mass of potassium nitrate dissolved in $100\text{ cm}^3$ of water at $90^{\circ}\text{C}$.
(d(ii))[2]
Using the graph, find the mass of potassium nitrate that crystallises when this solution is cooled from $90^{\circ}\text{C}$ to $20^{\circ}\text{C}$.