C22 Enthalpy And Entropy Flashcards
Define lattice enthalpy
The formation of 1 mole of ionic lattice from gaseous ions under standard conditions
What does a more exothermic lattice enthalpy mean
More exothermic = more stronger ionic bonds
Why’s it not possible to measure lattice enthalpy directly
It’s not possible to form 1 mole of ionic solid from its gaseous ions
Define standard enthalpy change of solution
Enthalpy change that takes place when 1 mole of a solute is completely dissolved in water under standard conditions
Define enthalpy change of hydration
The enthalpy change that takes place when dissolving 1 mole of gaseous ions in water
What’s are the factors that impact the size of lattice enthalpy
Size of ions involved
Charges on the ions
Ionic bond strength
Which ions have more negative lattice enthalpy values? Smaller / larger ions? Why?
Smaller ions because they can get closer hence more stronger attraction
Describe hydration
When an ionic lattice is broken the ions become part of the solution.
POS ions get attracted towards slightly neg oxygen and neg ions attracted towards slightly pos hydrogen
What factors impact the magnitude of the hydration enthalpy
Size of the ion
Charge on the ions
Define entropy
A measure of the dispersal of energy in a system which is greater when the system is more disordered
What’s the symbol of entropy
S
Solid or gas, which is more disordered
Gas
What’s the unit of standard entropy
JK^-1 mol^-1
How does temperature affect entropy
The greater temperature particles have more energy and move more. Thus the arrangement of particles become more random.
More random arrangement = higher entropy
When a solid ionic lattice is dissolved in solution what happens to entropy
Entropy increases because the ions are more disordered
How does change in number of gas molecules in a reaction affect entropy
Increase in number of gas molecules = increase in entropy
Decrease in number of gas molecules = decrease in entropy
For a reaction to occur spontaneously delta G must be pos or neg
Negative
What are the limitations of the predictions of feasibility made by using delta G
Reaction may have high activation energy
Rate of reaction may be very slow
Define lattice enthalpy
Formation of 1 mole of ionic lattice from gaseous ions under standard conditions
What does a more exothermic lattice enthalpy mean
More exothermic = more stronger ionic bonds
Why is it not possible to measure lattice enthalpy directly
It is not possible to form 1 mole of ionic solid from its gaseous ions
Define enthalpy change of solution
Enthalpy Change that takes place when 1 mole of a solute is completely dissolved in water under standard conditions
Define enthalpy change of hydration
The enthalpy change that takes place when dissolving one mole of gaseous ions in water
What are the factors that impact the size of lattice enthalpy
Size of ions involved
Charges on the ions
Ionic bond strength
Which ions have more negative lattice enthalpy values? Smaller/larger ions? Why?
Smaller ions because they can get closer hence more stronger attraction
Describe hydration
When an ionic lattice is broken the ions become part of the solution.
Positive ions get attracted towards slightly negative oxygen and negative ions get attracted towards slightly positive hydrogen
What are the factors that impact the magnitude of the enthalpy of hydration
Size of the ions
Charge on the ions
