A clear visual guide to determining the enthalpy of neutralisation using coffee-cup calorimetry, combining the practical method with a complete worked calculation and evaluation of the experiment.

The example uses the reaction between strontium hydroxide and nitric acid:

Sr(OH)₂(aq) + 2HNO₃(aq) → Sr(NO₃)₂(aq) + 2H₂O(l)

with the net ionic equation:

H⁺(aq) + OH⁻(aq) → H₂O(l)

The resource emphasises the important definition:

The enthalpy of neutralisation is the enthalpy change when 1 mole of water is formed.

Students are guided through the complete calculation, including:

Adding the two solution volumes together to obtain the total volume of solution being heated.
Calculating heat gained by the solution using Q = mcΔT.
Calculating the moles of acid and alkali and identifying the limiting reagent.
Calculating ΔH = −Q/n for the reaction as written.
Recognising that one mole of Sr(OH)₂ produces two moles of H₂O.
Converting the enthalpy change for the reaction into the enthalpy of neutralisation per mole of water formed.
Comparing the experimental result with the typical strong acid–strong base value of approximately −57 to −58 kJ mol⁻¹.

The worked experiment uses a realistic temperature rise of 6.0 K, deliberately producing a value that is less exothermic than the theoretical value because of experimental heat losses.

Two important assumptions in coffee-cup calorimetry calculations are highlighted:

1. The specific heat capacity of the solution is assumed to be 4.18 J g⁻¹ K⁻¹ — the same as water.

2. The density of the solution is assumed to be 1.00 g cm⁻³ — allowing the total solution volume in cm³ to be treated as the same numerical value as its mass in grams.

The resource also examines heat loss, experimental error and practical improvements, including nested polystyrene cups, a tight-fitting lid, continuous stirring and temperature-time extrapolation.

A particularly useful teaching point is the distinction between:

ΔH for the reaction as written
and
ΔH of neutralisation for the formation of exactly 1 mole of H₂O.

Suitable for GCSE, IGCSE and A-level Chemistry, especially for teaching energetics, calorimetry, limiting reagents, enthalpy calculations, neutralisation and evaluation of experimental procedures.

The accompanying animated GIF presents the experiment, calculations, explanations and improvements sequentially, making it suitable for classroom teaching, revision and independent study.