Electrochemistry - Standard Hydrogen Electrode
- The standard hydrogen electrode (SHE) is a reference electrode that provides a baseline to measure standard electrode potentials.
- It is constructed with a platinum electrode immersed in an acidic solution with 1M hydrogen ions (H+).
- The electrode potential of the SHE is defined as zero volts.
- It is often used as a reference for other half-cell electrode potentials.
- The reduction potential of any half-cell can be determined by measuring the potential difference between it and the SHE.
- The SHE is denoted as:
- Pt(s) | H2(g) (1 atm) | H+(aq) (1M)
- Standard electrode potential (E°) of the SHE is considered to be zero volts by convention.
Electrochemistry - Nernst Equation
- The Nernst equation is used to calculate the electrode potential of a half-cell under non-standard conditions.
- It relates the electrode potential (E) of a half-cell to the concentration (c) of the oxidized or reduced species.
- The Nernst equation is given as:
- E = E° - (RT/nF) ln(c)
- E: Electrode potential under non-standard conditions (V)
- E°: Standard electrode potential (V)
- R: Gas constant (8.314 J/(mol·K))
- T: Temperature (K)
- n: Number of moles of electrons transferred in the balanced reduction/oxidation equation
- F: Faraday’s constant (96,485 C/mol)
Electrochemistry - Cell Potential
- The cell potential (Ecell) represents the total potential difference between the two electrodes of a galvanic cell.
- It is also known as the electromotive force (EMF) of the cell.
- The cell potential is determined by the difference in electrode potentials of the two half-cells.
- It can be calculated using the following equation:
- Ecell = Ered(cathode) - Ered(anode)
- Ecell: Cell potential (V)
- Ered(cathode): Reduction potential of the cathode (V)
- Ered(anode): Reduction potential of the anode (V)
Electrochemistry - Cell Notation
- Cell notation is a shorthand representation of the components and reactions occurring in an electrochemical cell.
- It consists of anode, cathode, and salt bridge separated by vertical lines.
- The anode is written on the left side, and the cathode is written on the right side.
- Double vertical lines represent the salt bridge.
- Anode and cathode reactions are denoted with arrows pointing towards the right.
- For example:
- Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s)
Electrochemistry - Standard Reduction Potentials
- Standard reduction potentials (E°) are a measure of the tendency of species to get reduced.
- They indicate how easily a species is reduced compared to the standard hydrogen electrode (SHE).
- Standard reduction potentials are measured under standard conditions of 1M concentration, 1 atm pressure, and 298K temperature.
- Lower E° values indicate a higher tendency to get reduced, while higher E° values indicate a lower tendency.
- The more positive the E° value, the stronger the oxidizing agent it represents.
Electrochemistry - Relationship between Cell Potential and Gibbs Free Energy
- The relationship between cell potential (Ecell) and Gibbs free energy (ΔG) is given by the equation:
- ΔG = -nFEcell
- ΔG: Gibbs free energy change (J)
- n: Number of moles of electrons transferred
- F: Faraday’s constant (96,485 C/mol)
- Ecell: Cell potential (V)
- The negative sign indicates that a spontaneous reaction will have a negative value of ΔG and a positive value of Ecell.
Electrochemistry - Relationship between Cell Potential and Equilibrium Constant
- The cell potential of a galvanic cell can also be related to the equilibrium constant (K) of the overall reaction.
- The relationship is given by the equation:
- This equation is derived from the Nernst equation and can be used to determine the equilibrium constant if the cell potential is known, or vice versa.
- The natural logarithm of the equilibrium constant allows the conversion between the thermodynamic and electrochemical properties.
Electrochemistry - Batteries
- Batteries are portable sources of electrical energy that utilize electrochemical reactions.
- They consist of one or more cells connected in series or parallel to increase voltage or current.
- The most common types of batteries are:
- Primary batteries: Designed for one-time use, cannot be recharged (e.g., alkaline batteries)
- Secondary batteries: Rechargeable batteries, can be reused multiple times (e.g., lead-acid batteries, lithium-ion batteries)
- Battery efficiency and capacity depend on the chemical reactions occurring at the electrodes.
Electrochemistry - Corrosion
- Corrosion is the gradual destruction or degradation of a material by chemical reaction with its environment.
- It often occurs due to electrochemical reactions involving the material.
- The most common form of corrosion is the rusting of iron in the presence of moisture and oxygen.
- Corrosion can be prevented or minimized by using protective coatings, corrosion inhibitors, or cathodic protection techniques.
Electrochemistry - Standard Hydrogen Electrode
- The standard hydrogen electrode (SHE) is a reference electrode.
- It consists of a platinum electrode immersed in an acidic solution.
- The electrode potential of the SHE is defined as zero volts.
- It is used as a reference to measure standard electrode potentials.
- The SHE is denoted as: Pt(s) | H2(g) (1 atm) | H+(aq) (1M).
Electrochemistry - Nernst Equation
- The Nernst equation calculates the electrode potential of a half-cell.
- It relates the potential to the concentration of species.
- The Nernst equation: E = E° - (RT/nF) ln(c).
- E: Electrode potential under non-standard conditions (V).
- E°: Standard electrode potential (V).
Electrochemistry - Cell Potential
- Cell potential (Ecell) represents the total potential difference in a galvanic cell.
- It is the difference in electrode potentials of the two half-cells.
- Cell potential can be calculated using the equation: Ecell = Ered(cathode) - Ered(anode).
- Ecell: Cell potential (V).
Electrochemistry - Cell Notation
- Cell notation is a shorthand representation of electrochemical cells.
- It includes anode, cathode, and salt bridge.
- Anode is written on the left, cathode on the right.
- Double vertical lines represent the salt bridge.
Electrochemistry - Standard Reduction Potentials
- Standard reduction potentials (E°) measure the tendency to get reduced.
- They compare the species to the standard hydrogen electrode.
- E° values are measured under standard conditions.
- Lower E° values indicate a higher tendency to get reduced.
- Higher E° values indicate a lower tendency.
Electrochemistry - Standard Hydrogen Electrode
- The standard hydrogen electrode (SHE) is a reference electrode that provides a baseline to measure standard electrode potentials.
- It is constructed with a platinum electrode immersed in an acidic solution with 1M hydrogen ions (H+).
- The electrode potential of the SHE is defined as zero volts.
- It is often used as a reference for other half-cell electrode potentials.
- The reduction potential of any half-cell can be determined by measuring the potential difference between it and the SHE.
Electrochemistry - Nernst Equation
- The Nernst equation is used to calculate the electrode potential of a half-cell under non-standard conditions.
- It relates the electrode potential (E) of a half-cell to the concentration (c) of the oxidized or reduced species.
- The Nernst equation is given as:
- E = E° - (RT/nF) ln(c)
- E: Electrode potential under non-standard conditions (V)
- E°: Standard electrode potential (V)
- R: Gas constant (8.314 J/(mol·K))
- T: Temperature (K)
- n: Number of moles of electrons transferred in the balanced reduction/oxidation equation
- F: Faraday’s constant (96,485 C/mol)
Electrochemistry - Cell Potential
- The cell potential (Ecell) represents the total potential difference between the two electrodes of a galvanic cell.
- It is also known as the electromotive force (EMF) of the cell.
- The cell potential is determined by the difference in electrode potentials of the two half-cells.
- It can be calculated using the following equation:
- Ecell = Ered(cathode) - Ered(anode)
- Ecell: Cell potential (V)
- Ered(cathode): Reduction potential of the cathode (V)
- Ered(anode): Reduction potential of the anode (V)
Electrochemistry - Cell Notation
- Cell notation is a shorthand representation of the components and reactions occurring in an electrochemical cell.
- It consists of anode, cathode, and salt bridge separated by vertical lines.
- The anode is written on the left side, and the cathode is written on the right side.
- Double vertical lines represent the salt bridge.
- Anode and cathode reactions are denoted with arrows pointing towards the right.
- For example:
- Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s)
Electrochemistry - Standard Reduction Potentials
- Standard reduction potentials (E°) are a measure of the tendency of species to get reduced.
- They indicate how easily a species is reduced compared to the standard hydrogen electrode (SHE).
- Standard reduction potentials are measured under standard conditions of 1M concentration, 1 atm pressure, and 298K temperature.
- Lower E° values indicate a higher tendency to get reduced, while higher E° values indicate a lower tendency.
- The more positive the E° value, the stronger the oxidizing agent it represents.
Electrochemistry - Relationship between Cell Potential and Gibbs Free Energy
- The relationship between cell potential (Ecell) and Gibbs free energy (ΔG) is given by the equation:
- ΔG = -nFEcell
- ΔG: Gibbs free energy change (J)
- n: Number of moles of electrons transferred
- F: Faraday’s constant (96,485 C/mol)
- Ecell: Cell potential (V)
- The negative sign indicates that a spontaneous reaction will have a negative value of ΔG and a positive value of Ecell.
Electrochemistry - Relationship between Cell Potential and Equilibrium Constant
- The cell potential of a galvanic cell can also be related to the equilibrium constant (K) of the overall reaction.
- The relationship is given by the equation:
- This equation is derived from the Nernst equation and can be used to determine the equilibrium constant if the cell potential is known, or vice versa.
- The natural logarithm of the equilibrium constant allows the conversion between the thermodynamic and electrochemical properties.
Electrochemistry - Batteries
- Batteries are portable sources of electrical energy that utilize electrochemical reactions.
- They consist of one or more cells connected in series or parallel to increase voltage or current.
- The most common types of batteries are:
- Primary batteries: Designed for one-time use, cannot be recharged (e.g., alkaline batteries)
- Secondary batteries: Rechargeable batteries, can be reused multiple times (e.g., lead-acid batteries, lithium-ion batteries)
- Battery efficiency and capacity depend on the chemical reactions occurring at the electrodes.
Electrochemistry - Corrosion
- Corrosion is the gradual destruction or degradation of a material by chemical reaction with its environment.
- It often occurs due to electrochemical reactions involving the material.
- The most common form of corrosion is the rusting of iron in the presence of moisture and oxygen.
- Corrosion can be prevented or minimized by using protective coatings, corrosion inhibitors, or cathodic protection techniques.