The diagram shows the highest temperatures reached for $0.10\,\text{mol dm}^{-3}$ and $0.50\,\text{mol dm}^{-3}$ $\text{HCl(aq)}$. The starting temperature of $\text{NaOH(aq)}$ and the $\text{HCl(aq)}$ in every experiment is $20.0\,^{\circ}\text{C}$. Fill in the table with the highest temperatures and the temperature changes.
The temperature change for $0.70\,\text{mol dm}^{-3}$ $\text{HCl(aq)}$ is anomalous. Suggest what the student should do to check that this temperature change is anomalous.
Plot temperature change on the y-axis against $\text{HCl(aq)}$ concentration on the x-axis on the grid.
Draw one straight line of best fit for concentrations up to $0.90\,\text{mol dm}^{-3}$ and a second straight line through the other three points. Extend both straight lines until they meet.
Use the graph to find the concentration of $\text{HCl(aq)}$ that gives a temperature change of $5.4\,^{\circ}\text{C}$.
Use the graph to find the temperature change for $1.40\,\text{mol dm}^{-3}$ $\text{HCl(aq)}$.
Use the graph to find the minimum concentration of $\text{HCl(aq)}$ needed to neutralise all the $\text{NaOH(aq)}$.
Heat loss is a major source of error in this experiment. Suggest how the student can cut down the heat loss.