Heats of solution and neutralisation: Identify the incorrect statement about solution enthalpies and related concepts.

Introduction / Context:
Thermochemistry of solutions involves heats of mixing, solution, hydration, and neutralisation. Distinguishing which statements are valid is important for designing dissolution steps, acid–base neutralisations, and assessing energy effects in process streams and analytical titrations.

Given Data / Assumptions:

• Dilute solutions behave nearly ideally for strong electrolytes; weak electrolytes may require dissociation considerations.
• Standard reference states enable comparisons of heats of solution and hydration.
• Heats of mixing data can yield partial molar and integral properties if composition-dependent measurements are available.

Concept / Approach:
The integral heat of solution (at a specified final composition) can be obtained from enthalpy of mixing data by integrating composition-dependent partial molar enthalpies or using calorimetric measurements across concentrations. Weak acid or base neutralisations release less heat than strong/strong pairs because energy is consumed to ionise the weak species. Hydrate heats relate to differences between anhydrous and hydrated dissolution enthalpies. Enthalpy of dissolution depends on identity, concentration, and temperature, not just on the solute amount.

Step-by-Step Solution:
Examine (a): claims “cannot be calculated” from mixing data. This is incorrect; with proper thermodynamic data, integral heats can indeed be derived.Examine (b): true—weak species require ionisation, reducing net exothermicity compared with strong acid–strong base (≈ −57 kJ/mol water formed).Examine (c): true—definitionally relates hydrate dissolution to anhydrous dissolution and hydration enthalpy.Examine (d): true—enthalpy of solution depends on multiple factors including composition and temperature.

Verification / Alternative check:
Thermodynamic relationships among integral/partial molar quantities and calorimetric data sets are well established; many handbooks tabulate integral heats of solution obtained via mixing data.

Why Other Options Are Wrong:
Options (b), (c), and (d) are consistent with standard solution thermochemistry and practical calorimetry.

Common Pitfalls:
Confusing integral vs. differential (partial) heats; assuming heats are composition-independent; overlooking ionisation of weak electrolytes in neutralisation.

Final Answer:
The integral heat of solution of either component cannot be calculated from heat of mixing data.