Summary & Master Memory Capsule

The Whole Chapter in One Glance

Electrochemistry connects redox reactions with electricity. A galvanic cell turns a spontaneous reaction into current; an electrolytic cell uses current to drive a non-spontaneous one. The Nernst equation links potential to concentration; thermodynamics links it to $\Delta G$ and $K_c$. Conductance describes how solutions carry current; Kohlrausch's law dissects it ion by ion; Faraday's laws quantify electrolysis; and batteries, fuel cells and corrosion are the real-world payoff.

Slot every concept and numerical into one of these six branches.

Master Formula Sheet

Cell potential: $E^\circ_{cell}=E^\circ_{cathode}-E^\circ_{anode}$ (reduction potentials). Positive $E^\circ_{cell}$ → spontaneous.

Nernst equation (298 K): $E_{cell}=E^\circ_{cell}-\dfrac{0.059}{n}\log Q$

Thermodynamic links:

• $\Delta_r G^\circ = -nFE^\circ_{cell}$
• $E^\circ_{cell}=\dfrac{0.059}{n}\log K_c$
• $w_{max}=nFE^\circ_{cell}$

Conductance:

• Conductivity $\kappa=\dfrac{1}{R}\times\dfrac{l}{A}$, or $\kappa=G^*\!\times\!\dfrac{1}{R}$ when cell constant $G^*=\dfrac{l}{A}$
• Molar conductivity $\Lambda_m=\dfrac{\kappa\times1000}{c}$ (S cm² mol⁻¹)
• Kohlrausch: $\Lambda^\circ_m=\nu_+\lambda^\circ_++\nu_-\lambda^\circ_-$
• Degree of dissociation $\alpha=\dfrac{\Lambda_m}{\Lambda^\circ_m}$; $K_a=\dfrac{c\alpha^2}{1-\alpha}$

Faraday's laws: $m=ZIt$; moles deposited $=\dfrac{It}{nF}$; $1\text{ F}=96500$ C mol⁻¹.

Constants: $\dfrac{2.303RT}{F}=0.059$ V at 298 K; $E^\circ_{SHE}=0$.

Quick Comparison Tables

Galvanic vs Electrolytic cell

Feature	Galvanic	Electrolytic
Energy	Chemical → electrical	Electrical → chemical
Reaction	Spontaneous	Non-spontaneous
Anode	Negative	Positive
Cathode	Positive	Negative
(Oxidation at anode, reduction at cathode in both)

Strong vs Weak electrolyte (conductivity)

Feature	Strong	Weak
Dissociation	Complete	Partial
$\Lambda_m$ vs $\sqrt{c}$	Straight line	Steep curve near c=0
$\Lambda^\circ_m$	By extrapolation	By Kohlrausch's law

Primary vs Secondary cell

Feature	Primary	Secondary
Rechargeable	No	Yes
Examples	Dry cell, mercury cell	Lead storage, Ni-Cd

Last-Minute Memory Hooks

• An Ox, Red Cat: Anode = Oxidation, Cathode = Reduction (in both cell types). Only the terminal sign flips between galvanic and electrolytic.
• $E^\circ_{cell}=E^\circ_{cathode}-E^\circ_{anode}$; positive → spontaneous → $\Delta G<0$ → $K_c>1$.
• Nernst: more product / less reactant lowers $E_{cell}$. Dead cell: $E_{cell}=0$, $Q=K_c$.
• 0.059 is the magic number at 298 K — appears in Nernst and in $E^\circ=\frac{0.059}{n}\log K_c$.
• On dilution: $\kappa$ down, $\Lambda_m$ up (opposite directions).
• Kohlrausch combo for acetic acid: CH₃COONa + HCl − NaCl.
• Faraday recipe: $Q=It \to$ mol e⁻ $=Q/96500 \to$ mol product $\div n \to$ mass.
• Mercury cell = constant voltage (no ionic concentration change). Lead battery acid dilutes on discharge.
• Rusting needs water + O₂; protect with Zn/Mg (more reactive, sacrificial).

One-line revision flow: Galvanic cell → electrode potential & SHE → Nernst → ΔG & Kc → conductance & Kohlrausch → electrolysis & Faraday → batteries, fuel cells, corrosion.