Acid/Base Calorimetry

Neutralise equal volumes of HCl and NaOH in a simple coffee-cup calorimeter, record the temperature rise, and calculate the molar enthalpy of neutralisation using q = m c ΔT and ΔH = −q/n.

1. Assemble a coffee-cup calorimeter (polystyrene cup with lid), magnetic stirrer, stir bar, and calibrated thermometer or probe.
2. Measure 50.0 mL of ~1.0 M HCl and 50.0 mL of ~1.0 M NaOH in separate cylinders.
3. Place the stir bar and the acid into the cup; insert probe through the lid; stir gently and record a stable initial temperature (≈2–3 min).
4. Quickly add the base all at once, replace the lid, and stir continuously while recording temperature every 5–10 s.
5. Identify the maximum temperature; take ΔT = Tmax − Tinitial.
6. Estimate solution mass m by volume×density (≈100 g if 100 mL total); use c ≈ 4.18 J g⁻¹ K⁻¹; compute q = m c ΔT.
7. Determine limiting moles n (e.g., n = 0.0500 mol if 50.0 mL of 1.00 M); calculate ΔHneut = −q/n (report in kJ mol⁻¹; include sign).

Acid Base Neutralization Calorimetry Lab - 100patoms:

CHEM 111 Exp#12 - Calorimetry: Enthalpy of Neutralization Reactions - Dr. Carolynn Arpin:

📄 Understanding Enthalpy of Neutralisation - Catalyst: https://www.catalystchemistry.com.au/resources/mod6-acid-bases/iq1/5-enthalpy-of-neutralisation

• Account for calorimeter heat capacity by determining a calorimeter constant from a hot–cold water calibration.
• Repeat with weak acids or weak bases at the same formal concentration to compare enthalpies and heat loss effects.
• Vary initial concentrations or volumes while keeping n the same.

• Wear splash goggles, lab coat, and appropriate gloves.
• HCl and NaOH are corrosive; avoid skin/eye contact and clean spills with plenty of water.
• Do not seal the cup; gases and heat must vent.
• Label acids and bases clearly; use separate, clean glassware for each.
• Neutralise waste before disposal according to local rules; wash hands after the experiment.

• Why is ΔHneut negative for strong acid–base reactions? (The reaction is exothermic; the solution gains heat that came from chemical potential energy.)
• Why are values for strong acid–strong base near −57 kJ/mol? (They all essentially form 1 mol of water from H⁺ and OH⁻, with similar ionic solutions and minimal side processes.)
• What assumptions were made in q = m c ΔT? (Density ≈ 1 g mL⁻¹, c ≈ water, negligible calorimeter heat capacity and heat loss.)
• How would including a calorimeter constant change ΔH? (It increases q to account for heat absorbed by the cup, making ΔH more negative in magnitude.)
• If acid and base are not equimolar, which n should be used? (Use moles of the limiting reactant, equal to moles of water formed.)