Hard-difficulty flashcards covering advanced A-Level Chemistry concepts including Gibbs free energy, electrode potentials, transition metal stereochemistry, and reaction mechanisms.
20 cards
Front
Born-Haber Cycles: Calculating Lattice Energy
Back
Used to determine lattice energy (U) indirectly. The cycle sum must equal the enthalpy of formation. If experimental U > theoretical U, the bonding has greater covalent character than the ionic model predicts, due to polarization of the anion by the cation.
Front
Entropy Change (ΔS) and Spontaneity
Back
ΔS = ΣS(products) - ΣS(reactants). A process is spontaneous if ΔStotal (system + surroundings) > 0. This can occur even if ΔSsystem is negative, provided the enthalpy change is sufficiently exothermic to increase the entropy of the surroundings (ΔSsurr = -ΔH/T).
Front
Gibbs Free Energy (ΔG)
Back
ΔG = ΔH - TΔS. A reaction is feasible (spontaneous) if ΔG < 0. This equation combines enthalpy and entropy effects. Note that 'feasible' refers to thermodynamic possibility, not kinetic rate (activation energy).
Front
Gibbs Free Energy and Equilibrium Constant (Kc)
Back
Linked by ΔG° = -RT ln Kc. If ΔG° is negative, ln Kc is positive, so Kc > 1 (products favored). If ΔG° is positive, ln Kc is negative, so Kc < 1 (reactants favored). R is the gas constant (8.31 J mol⁻¹ K⁻¹) and T is temperature in Kelvin.
Front
Standard Electrode Potential (E°)
Back
The potential of a half-cell relative to the Standard Hydrogen Electrode (SHE) at standard conditions. E° is an intensive property (independent of moles). It is a measure of thermodynamic tendency, not rate. A more positive E° indicates a stronger oxidizing agent.
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