A group of students performed an experiment to measure the temperature rise during a neutralisation reaction between nitric acid (HNO3\text{HNO}_3HNO3) and potassium hydroxide (KOH\text{KOH}KOH) 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 potassium 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 maximum temperature?
In a second experiment, a student mixed 50.0 cm350.0\text{ cm}^350.0 cm3 of 1.40 mol/dm31.40\text{ mol/dm}^31.40 mol/dm3 nitric acid with 50.0 cm350.0\text{ cm}^350.0 cm3 of 1.40 mol/dm31.40\text{ mol/dm}^31.40 mol/dm3 potassium hydroxide solution. The temperature rose from 19.5 ∘C19.5\ ^\circ\text{C}19.5 ∘C to 28.1 ∘C28.1\ ^\circ\text{C}28.1 ∘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 potassium 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.
