Galvanic Cells

The Setup

Essentially, each half-reaction is isolated within a separate chamber, in a solution. Electrodes, the reaction site, are placed within the chambers and are connected to each other with a conductive wire. A salt bridge also connects the solutions together. 

The Reduction-Oxidation Mechanism

Cathode: The electrode that hosts the reduction half-reaction. 

Anode: The electrode that hosts the oxidation half-reaction. 

The anode spontaneously reacts with the solution, gradually dissolving as its atoms ionize into cations and dissociate into the solution. The reduction half-reaction can be represented as: 

X (s) → Xⁿ⁺ (aq) + ne⁻ 

The electrons produced from the ionization travel from the anode to the cathode through the conductive wire. The cathode then spontaneously donates the electrons to the cations, converting them to atoms which deposit onto the cathode. The oxidation half-reaction can be represented as: 

Yⁿ⁺ (aq) + ne⁻ → Y (s) 

Overall reaction equation: 

X (s) + Yⁿ⁺ (aq) → Xⁿ⁺ (aq) + Y (s) (ΔG < 0)

The Purpose of the Salt Bridge

Salt Bridge: A tube filled with a concentrated solution of an inert ionic solute that connects to the chambers. 

The salt bridge maintains the neutrality of the solutions in the chambers. 

In the cathode chamber, cations of the reaction decrease in concentration and deposit as neutral atoms as a result of reduction. In response to the loss, inert cations from the salt bridge flow into the solution to balance the charges. 

In the anode chamber, atoms are released into the solution as cations after undergoing oxidation. To counter the influx of cations, inert anions from the salt bridge are released into the solution to balance the charges. 

"Anions to anode, cations to cathode."