Galvanic Cells

• Galvanic cell
• Galvanic cells convert chemical energy to electrical energy
• Galvanic cells force redox reactions to occur through a wire to produce electricity
• Galvanic cells are present in devices like phones, laptops, cameras, watches, and cars
• A cell is an individual galvanic reaction, while a battery consists of multiple cells
• Key Terminology
• Anode: site of oxidation, negative polarity
• Cathode: site of reduction, positive polarity
• Electrolyte: substance that conducts electricity
• External circuit: path for electron flow
• Salt bridge: maintains neutrality by allowing ion flow between half cells
• Salt Bridge
• Salt bridge ensures neutrality in galvanic cells by allowing ion flow between half cells
• If the salt bridge is removed, the circuit stops as neutrality is lost
• Example: KNO3 is a suitable salt bridge
• Inert Electrode
• Inert electrodes like graphite or platinum do not react but can catalyze reactions
• Inert electrodes are used when a gas is formed in a half equation
• Hydrogen gas acts as the electrode in this case
• Inert electrodes like platinum or graphite can also be present
• Platinum or graphite is referred to as the cathode even though the reaction occurs through the H2 gas
• Current flows from the anode to the cathode
• Negative 7.6 volts indicates the charge and the direction of the voltage
• Negative voltage indicates the opposite direction to what the reader reads
• Voltage is determined by the potential difference between two half cells
• Standard electrode potential is measured by connecting every half cell to a standard hydrogen half cell
• Lead has a standard electrode potential of -0.13, while zinc has a standard electrode potential of -0.76
• Lead is a weaker reductant than zinc based on their electrode potentials
• Silver has a standard electrode potential of +0.8 compared to hydrogen
• Silver is on the opposite side of hydrogen in terms of electrode potential
• Strong oxidants tend to cause reduction, while strong reductants tend to cause oxidation
• Comparing electrode potentials helps determine the voltage output of a galvanic cell
• Replacing Cu2+ with Mg2+ will not generate electricity spontaneously due to the strength of the oxidant and reductant
• In a series of reactions, always choose the strongest oxidant and reductant for a spontaneous reaction
• Calculating the potential difference of a cell involves subtracting the reduction potential from the oxidation potential
• The potential difference of the cell should always result in a positive value
• Electrons flow from the anode to the cathode in a circuit
• Practice questions often involve identifying the anode and cathode, and calculating the potential difference between cells