A group of students performed an experiment to measure the temperature rise during a neutralisation reaction between hydrochloric acid (HCl\text{HCl}HCl) and sodium hydroxide (NaOH\text{NaOH}NaOH) solution.
The teacher asked the students about their experimental method: Why is it better to use a volumetric pipette instead of a measuring cylinder to measure the sodium hydroxide solution?
Explain why carrying out the reaction in a polystyrene cup rather than a glass beaker improves the accuracy of the temperature measurement.
What step should the students perform immediately after adding the acid and before recording the temperature?
In a second experiment, a student mixed 40.0 cm3 of 1.20 mol/dm3 hydrochloric acid with 40.0 cm3 of 1.20 mol/dm3 sodium hydroxide solution. The temperature rose from 20.2 ∘C20.2\ ^{\circ}\text{C}20.2 ∘C to 26.7 ∘C26.7\ ^{\circ}\text{C}26.7 ∘C. Calculate the heat energy change, in Joules (J\text{J}J), using the expression:
heat energy change=total volume of mixture×4.2×temperature change \text{heat energy change} = \text{total volume of mixture} \times 4.2 \times \text{temperature change} heat energy change=total volume of mixture×4.2×temperature changeCalculate the amount, in moles, of sodium hydroxide neutralised.
Calculate the molar enthalpy change (ΔH\Delta HΔH), in kJ/mol\text{kJ/mol}kJ/mol, for the neutralisation. Include the correct sign (+ or -) in your answer.
