What is a redox reaction?
A chemical reaction in which electrons are transferred
Must have both oxidation and reduction happening for the reaction to occur
What is a reduction reaction?
A process in which electrons are gained by an entity
What is an oxidation reaction?
A process in which electrons are lost by an entity
What are the two ways you can determine if a redox reaction takes place?
Change in oxidation state
Balanced half reactions
What is an oxidation state?
The apparent jet charge an atom would have if it owned all the electrons in a covalent bond
What are the steps to determining oxidation states?
- Assign common oxidation numbers
- The total of all the oxidation numbers equals the net charge on the molecule
- Any unknown oxidation number is determined algebraically from known oxidation numbers and the net charge of the entity
What is the oxidizing agent?
Causes oxidation by removing electrons (gaining) from another substance in a redox reaction
What is the reducing agent?
Cause reduction by donating electrons (losing) to another substance in a redox reaction
What is a half reaction?
Balanced chemical equations that represent either a loss or gain of electrons
One half reaction represents reduction
The other fair reaction represents oxidation
What are the steps for determining complex half reactions?
- List all of the species present
- Use the table in the data booklet to determine the strongest OA and the strongest RA
- Write out the two half reactions (flip the oxidation reaction)
- Balance to cancel electron if needed
- Write out net ionic equation
How can you determine the spontaneity of redox reactions using the data booklet?
If the SOA is above the SRA it is spontaneous
If the SOA is below the SRA it is non-spontaneous
How can you determine the spontaneity of redox reactions using the net electrical potential?
If the net EP is positive it is spontaneous
If the net EP is negative it is non-spontaneous
What are the steps for balancing redox equations using oxidation numbers?
- Assign oxidation numbers and identify atoms/ions whose oxidation numbers change
- Use the change in oxidation numbers to determine the number of electrons transferred per atom
- Determine the number of electrons transferred per reactant
- Use coefficients to balance electron charge in reactants and products
- Balance oxygen atoms using H2O and hydrogen atoms using H+
What is corrosion?
Natural process where a metal reacts to fork a more chemically stable form (oxidation)
What is refining?
Removal of impurities, how most metals are formed from ores (reduction)
What is a sacrificial anode?
A very strong reducing agent that will be oxidized
Protects a less reactive metal (weaker RA) from reacting/corroding/rusting/oxidizing
What is an electrical cell?
An electric cell converts chemical energy into not electrical energy
What are electric cells composed of?
Two electrodes and at least one electrolyte
What are electrodes?
Solid electrical conductors
The positive electrode is defined as the cathode
The negative electrode is defined as the anode
Electrons flow through the external circuit from anode to cathode
What is an electrolyte?
Aqueous electrical conductor
Ions travel internally in the solution
What is a voltaic cell?
Consists of two half cells separated by a porous boundary with solid electrodes connected by an external circuit
SOA undergoes reduction at the cathode (increases in mass)
SRA undergoes oxidation at the anode (decreases in mass)
What is a electrolytic cell?
Non spontaneous reaction
Two electrodes
At least one electrolyte
External power source
What is electrolysis?
The process of supplying electrical energy to force a non-spontaneous redox reaction to occur
What is a reference cell?
Used as a baseline for the comparison of redox half reactions
