Given an HCl and NaOH neutralization enthalpy of – 57.46 kJ/Kg mole, the calculated heat of water ionization is _____________ kJ/Kg mole?
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Answer: A. 57.46
Explanation
Water ionization is the exact reverse process of strong acid and strong base neutralization. Reversing a chemical reaction changes the sign of its corresponding enthalpy change value. The standard ionization heat of water equals the positive magnitude of the neutralization enthalpy. Water autoionization produces hydrogen and hydroxide ions in minute quantities at equilibrium. Enthalpy changes for reverse reactions share identical magnitudes but possess opposite algebraic signs. Thermochemical calculations require careful attention to reaction stoichiometry and directional sign conventions.
Analytical chemistry relies on water ionization constants to determine pH and pOH values. Thermodynamic modeling of aqueous systems incorporates accurate water dissociation enthalpy data. Power plant water chemistry control requires precise understanding of high-temperature ionization behavior. A negative value represents neutralization rather than the endothermic water ionization process. Multiplying by two represents stoichiometric errors rather than correct thermochemical reversal rules. Dividing the enthalpy value by two misinterprets the standard molar reaction basis.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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