AP Chemistry · Summary

Unit 9 summary

  1. Entropy rises when particles gain freedom: melting, boiling, dissolving, or more moles of gas. Count gas moles first.
  2. ΔS∘\Delta S^\circ = products minus reactants, each times its coefficient, in J/(mol·K).
  3. ΔG∘=ΔH∘−TΔS∘\Delta G^\circ = \Delta H^\circ - T\Delta S^\circ with ΔS∘\Delta S^\circ in kJ/(mol·K); negative means thermodynamically favorable, which says nothing about speed.
  4. When ΔH∘\Delta H^\circ and ΔS∘\Delta S^\circ share a sign, temperature decides; ΔG∘=−RTln⁡K\Delta G^\circ = -RT\ln K, so a negative ΔG∘\Delta G^\circ means K greater than 1.
  5. Oxidation at the anode, reduction at the cathode; electrons flow through the wire from anode to cathode, and ions move through the salt bridge.
  6. Ecell∘=Ecathode∘−Eanode∘E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}}, never multiplied by coefficients; ΔG∘=−nFEcell∘\Delta G^\circ = -nFE^\circ_{\text{cell}}.
  7. Electrolysis: q=Itq = It (seconds), moles of electrons = q/Fq/F, then use the electrons per ion to find moles and grams.
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