AQA A-Level Chemistry 7405
Atomic Structure
Amount of Substance
Bonding
Energetics and Thermodynamics
Kinetics
Chemical Equilibria
Redox and Electrochemistry
Acids and Bases
Periodicity and Group Chemistry
Period 3 Elements and Their Oxides
Transition Metals
Introduction to Organic Chemistry
Hydrocarbons
Halogenoalkanes, Alcohols and Organic Analysis
Carbonyls, Carboxylic Acids and Derivatives
Aromatic Chemistry and Amines
Polymers, Amino Acids, Proteins and DNA
Organic Synthesis, NMR and Chromatography
Energetics and Thermodynamics
Enthalpies of Solution and Hydration
- 3 things to know
- Papers 1 and 3
Overview
Enthalpy of solution and of hydration, and linking them through the lattice enthalpy.
What you need to know
Answer each one before you reveal it.
What determines whether the enthalpy of solution is exothermic or endothermic?
How does ion size affect the magnitude of enthalpy of hydration?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is the definition of enthalpy of solution?
Model answer
The enthalpy change when one mole of an ionic solid dissolves in sufficient water to form an infinitely dilute solution under standard conditions.
- 2
What is the definition of enthalpy of hydration?
Model answer
The enthalpy change when one mole of gaseous ions is dissolved in sufficient water to form an infinitely dilute solution under standard conditions.
- 3
What type of enthalpy change is the enthalpy of hydration — exothermic or endothermic?
Model answer
Exothermic.
- 4
Why is enthalpy of hydration always exothermic?
Model answer
Because ion-dipole bonds form between the ions and water molecules, releasing energy.
- 5
How can enthalpy of solution be calculated using a Hess's law cycle?
Model answer
By constructing a cycle linking lattice enthalpy, enthalpies of hydration of the ions, and enthalpy of solution.
- 6
What three enthalpy terms are related in the enthalpy cycle for dissolving an ionic compound?
Model answer
Lattice enthalpy, enthalpies of hydration of the cation and anion, and enthalpy of solution.
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