Redox and Standard Reduction Potential Table
Overview
- Seventh video on redox by Mr. Lim
- Topics covered:
- Standard reduction potential table
- Predicting displacement reactions
- Oxidation and reduction in galvanic cells
- Role of the hydrogen half-cell
Standard Reduction Potential Table
- Improved over reactivity series for predicting displacement reactions
- Tests all substances (metals and halogens) against each other
- Galvanic cells used to test oxidizing/reducing strength of substances
Galvanic Cells Recap
- Made up of two half-cells (oxidant and reductant forms)
- Each half-cell competes for electrons
- Electron flow direction can tell oxidation/reduction outcomes
- Examples with X+ and Y+ oxidants competing
Determining Anode and Cathode
- Electrons flow to the cathode
- Observation of color change indicates reduction/oxidation
- e.g., S+ (blue) becoming less blue indicates reduction to S solid
- Cathode: where reduction occurs (electron gain)
- Anode: the opposite electrode (electron loss)
Energy in Galvanic Cells
- Electron flow has energy, determined by oxidant/reductant strength
- Testing against standards helps predict redox behavior
- Example: R+ vs. S+, Q vs. S+ comparisons
Standard Hydrogen Half-Cell
- Assigned value of zero volts
- All other half-cells compared to it
- Rankings determined by whether substances can oxidize/reduce the hydrogen half-cell
- Placing in the ranking system:
- Above hydrogen: stronger oxidizing agents
- Below hydrogen: weaker oxidizing agents
Predicting Reactions Using the Table
- Downhill arrangement predicts spontaneous reactions
- Example: Zinc vs. Cadmium, downhill arrangement indicates Cd2+ wins
- Forward reaction (upper half-cell) and reverse reaction (lower half-cell)
Electrochemical Cell Examples
- Identifying half-cells, galvanic cell configuration:
- Determine anode and cathode based on electron flow and oxidation/reduction
- Electrode potentials and their respective reactions
- Standard half-cell reactions:
- Gain or loss of electrons indicates direction (reduction/oxidation)
- Direction of electron flow and movement of cations/anions in the salt bridge
Key Points
- Focus on the downhill arrangement for predicting reactions
- Stronger oxidizing agents are placed above in the reduction potential table
- Cathode (reduction) is always positive, anode (oxidation) is always negative in galvanic cells
Simplified Process
- Identify half-cells and their reactions
- Use downhill arrangement to predict reaction direction
- Follow standard rules: electrons flow to cathode, ions balance charge
- Apply to examples—understanding setup of galvanic cells and electron flow directions
Feel free to ask questions for clarification!