MODULE 5: Enthalpy and Entropy

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Total cards: 24•Content version: v4•Public deck•Updated: 8/1/2026

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Front (Question)

Entropy symbol:

Back (Answer)

Front (Question)

Order of highest to lowest entropy:

Back (Answer)

Gas, liquid, solid

Front (Question)

Entropy:

Back (Answer)

A measure of the dispersal of energy in a system which is greater, the more disordered a system

Front (Question)

Units of entropy:

Back (Answer)

J -1 K -1 mol -1

Front (Question)

Changes in entropy:

Back (Answer)

Changes to become more random = positive ΔS Changes to become less random = negative ΔS

Front (Question)

Standard entropy:

Back (Answer)

Entropy of one mole of a substance, under standard conditions

Front (Question)

Calculating entropy change:

Back (Answer)

ΔS = ΔS (products) - ΔS (reactants)

Front (Question)

Feasibility:

Back (Answer)

Whether a reaction is able to occur and is energetically feasible (spontaneous)

Front (Question)

Free energy change:

Back (Answer)

Overall change in energy during a chemical reaction, made up of enthalpy change and entropy

#10

Front (Question)

Gibbs equation:

Back (Answer)

ΔG = ΔH - TΔS ΔG = free energy change ΔH = enthalpy change T = temperature (K) ΔS = entropy change

#11

Front (Question)

Value of ΔG for a reaction to be feasible:

Back (Answer)

ΔG < 0

#12

Front (Question)

Limitations of predicting feasibility:

Back (Answer)

Gibbs free energy only takes into account a reaction’s feasibility, but not activation energy or rate of reaction- which may cause a reaction to not occur or be very slow

#13

Front (Question)

Lattice enthalpy: ΔlattH

Back (Answer)

Enthalpy change when one mole of an ionic compound is formed from its constituent gaseous ions under standard conditions

#14

Front (Question)

Use of lattice enthalpy:

Back (Answer)

Measure strength of an ionic bond in a giant ionic lattice

#15

Front (Question)

Standard enthalpy of formation: ΔfH

Back (Answer)

Enthalpy change when one mole of compound is formed from its constituent elements at standard state (state in standard conditions)

#16

Front (Question)

Standard enthalpy change of atomisation: ΔatH

Back (Answer)

Enthalpy change when one mole of gaseous atoms are formed in standard conditions

#17

Front (Question)

First ionisation energy: ΔIEH

Back (Answer)

Enthalpy change when one mole of electrons are removed from one mole of gaseous atoms to form one mole of gaseous 1+ ions

#18

Front (Question)

First electron affinity: ΔEAH

Back (Answer)

Enthalpy change when one mole of electrons is added to one mole of gaseous atoms to form one mole of gaseous 1- ions

#19

Front (Question)

Enthalpy change of solution: ΔsolH

Back (Answer)

Enthalpy change when one mole of solute dissolves in a solvent

#20

Front (Question)

Enthalpy change of hydration: ΔhydH

Back (Answer)

Enthalpy change when gaseous ions dissolve in water to form one mole of aqueous ions

#21

Front (Question)

Factors effecting lattice enthalpy and enthalpy change of hydration:

Back (Answer)

Ionic size and ionic charge

#22

Front (Question)

Effect of ionic size on lattice enthalpy:

Back (Answer)

• Ionic radius increases • Attraction between ions decreases • Lattice enthalpy less negative • Melting point decreases

#23

Front (Question)

Effect of ionic charge on lattice enthalpy:

Back (Answer)

• Ionic charge increases • Attraction between ions increases • Lattice enthalpy becomes more negative • Melting point increases

#24

Front (Question)

Effect of ionic size on enthalpy change of hydration:

Back (Answer)

• Ionic radius increases • Attraction between ion and water molecules increases • Enthalpy change of hydration less negative