CCEA A-Level Chemistry 1110
Formulae, Equations and Amounts of Substance
Atomic Structure
Bonding
Intermolecular Forces and Structure
Shapes of Molecules and Ions
Redox
The Halogens
Acid-Base Titrations
Qualitative Tests
Formulae and Amounts of a Substance
Nomenclature and Isomerism in Organic Chemistry
Alkanes
Alkenes
Halogenoalkanes
Alcohols
Infrared Spectroscopy
Energetics
Kinetics
Equilibrium
Group II Elements and Their Compounds
Lattice Enthalpy, Entropy and Free Energy
Rates of Reaction
Equilibrium and Acid-Base Equilibria
Isomerism
Aldehydes and Ketones
Carboxylic Acids
Derivatives of Carboxylic Acids
Aromatic Chemistry
Spectroscopy and Chromatography
Volumetric Analysis
Transition Metals
Electrode Potentials
Amines
Amides and Polymers
Amino Acids and Proteins
Energetics
Standard enthalpy of neutralisation
- 3 things to know
- Unit AS 2
Overview
Standard enthalpy of neutralisation and how the enthalpy of neutralisation is measured in the laboratory.
What you need to know
Answer each one before you reveal it.
Why is the enthalpy of neutralisation defined per mole of water rather than per mole of acid?
State the approximate value of the enthalpy of neutralisation for a strong acid and a strong alkali.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define the standard enthalpy of neutralisation.
Model answer
The standard enthalpy of neutralisation is the enthalpy change when an acid and a base react under standard conditions to form one mole of water.
- 2
Why is the enthalpy of neutralisation defined per mole of water rather than per mole of acid?
Model answer
Acids differ in the number of moles of hydrogen ions they can supply, so only the water produced gives a basis common to all of them.
- 3
State the approximate value of the enthalpy of neutralisation for a strong acid and a strong alkali.
Model answer
The value is close to −57 kJ mol⁻¹.
- 4
Why is almost the same value obtained for every strong acid and strong alkali pair?
Model answer
Both are fully ionised in solution, so in every case the only reaction taking place is the combination of hydrogen ions with hydroxide ions.
- 5
Write the ionic equation for the neutralisation of a strong acid by a strong alkali.
Model answer
The ionic equation is H⁺(aq) + OH⁻(aq) → H₂O(l).
- 6
Why is the enthalpy of neutralisation of ethanoic acid by sodium hydroxide less exothermic than that of hydrochloric acid?
Model answer
Ethanoic acid is only partly ionised, so energy has to be absorbed to complete its dissociation and less heat is released overall.
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