Lesson 12: Electrochemistry Cont. Flashcards
Electrochemistry Cont.
Nernst Equation (Def)
Used to calculate non standard cell potential.
Nernst Equation(s)
E = E° - (RT/nF)ln(q)
E = E° - (0.0592/n)log(q)
Free Energy (G) for Cell Potentials Equations (Nonstandard and Standard)
ΔG° = -nFE°
ΔG = -nFE
(E, E°, n, F, Q) What do they stand for?
E = non standard cell potential.
E° = standard cell potential.
n = number of electrons transferred (no +
or - sign)
F = Faraday’s constant
Q = Concentrations of products/reactants.
Faraday’s Constant (F) Definition
Amount of electrical charge on one mole of electrons.
Faraday’s Constant (F) Number and unit(s)
F = 96,500 coulomb/mol of electrons
F = 96,500 J/V*mol
The higher the voltage the (x) the flow of electrons?
- Higher
- Slower
Higher
(The higher the voltage the more spontaneous it is)
Coulomb (C)/(Q) Definition (Charge)
Quantity of charge that passes through a point in a circuit.
Current (Ampere Unit) (I) (current)
The amount of charge (coulombs) that flow past one point in a circuit every second.
1Ampere = coulombs/second
Cell Potential (measured in voltage)
Measure of potential difference between two half cells in an electrochemical cell.
(How strongly electrons are being pushed a circuit)
1 Volt = 1J/1Coloumb
Energy (Joules)
The capacity to supply heat or do work.
(K) (G°) (E°) for spontaneous reactions
(K) > 1
(G°) < 0
(E°) > 0
(K) (G°) (E°) for non spontaneous reactions
(K) < 1
(G°) > 0
(E°) < 0
(K) (G°) (E°) at Equilibrium
(K) = 1
(G°) = 0
(E°) = 0
When to use E = E° - (RT/nF)*ln(q)
If temperature is non standard.
When to use E = E° - (0.0592/n)*log(q)
If temperature is standard.
Concentration Cell
The concentration of the same ions are different in the two cells.
Concentration Cell (Equation)
Ecell = -(0.0592/n)*log(low/high)
Equilibrium Constant (Keq) - Dead Battery Equation (standard temp)
Log(Keq) = nE°/(0.0592)
Equilibrium Constant (Keq) - Dead Battery Equation (standard temp)
E°=RT/nF*ln(k)
Galvanic (Voltaic) Cell
Electrochemical cells in which spontaneous redox reactions produce electrical energy.
Electrochemical Cell
Device that can generate electrical energy from redox reactions or use
Battery
Portable, self-contained electrochemical power source that consists of one or more voltaic cells.
Lead-Acid Battery
Battery used in cars (can be recharged).
Alkaline Battery
Battery used in tv remotes and kids toys.
-Less charge than Lead-Acid battery.
-Not rechargeable.
-1.55V produced at room temp.
Three Types of Rechargeable Batteries
- Nickel-Cadmium
- Nickel-Metal-Hydride
- Lithium-Ion
Nickel-Cadmium Battery (Rechargeable) - How many cells, voltage, and impact on the environment?
Three cells, 1.30V, and bad for the environment(cadmium is a heavy metal).
Nickel-Metal-Hydride (Rechargeable) - (Same function as (x) battery and impact on the environment)
Same function as Nickel-Cadmium but uses metal alloy so better for the environment.
Lithium-Ion Battery (Beneficial and Use)
Beneficial because of how light lithium is.
Used for portable devices like cell phones.
Five Types of Batteries
- Lead-Acid (non-recharge).
- Alkaline (non-recharge).
- Nickel-Cadmium (rechargeable).
- Nickel-Metal-Hydride (rechargeable).
- Lithium-Ion (rechargeable).
Have No Fear Of Ice Cold Beer (Diatomic)
H2, N2, F2, I2, Cl2, Br2
Conductor
Substance or metal that allows electrons to flow through it. (Cathode and Anode)
Anode Cathode Charges Galvanic (Voltaic) Cells
Anode is negative (pushing electrons out)
Cathode is positive (drawing electrons in)
Anode Cathode Charges Electrolytic Cells (PANIC)
Anode is positive (electrons being forcibly removed by battery)
Cathode is negative (electrons being forcibly added by battery)
Anions get (x) at and Cations get (x) in electrolysis? (PANIC)
Anions oxidized attracted to positive anode.
Cations reduced - attracted to negative cathode)
(neutral atom remains).
Chemical Energy
Energy that is stored in the bonds between atoms and molecules.
1 volt = x/x
1joule/coulomb
Coulomb (Q) = x * x
amperes (I) * seconds (t)
Electrolysis Equation (mass of product)
((Initial amps)(t-seconds)(MM of product element)/nF)
= (mass of product)
Electrolysis Equation (moles of product)
(Initial amps)*(t-seconds)/nF)
= (mole of product)
Circuit
Closed loop that electrons can travel in.
Point (Circuit)
Specific location(s) of a circuit where components are connected.
(Terminal that connects a light bulb to a circuit)
(Power plug in wall)
Electrodes
Special class of conductors.
Component
Any part of an electrical circuit.
(battery, connecting wire, conductor, cathode, anode, etc).
Faraday’s Constant (Unit)
C/mole (C/mole)
Diatomic Molecules Mnemonic
Have No Fear Of Ice Cold Beer (Diatomic)
Are given Redox Equations at Equilibrium balanced in the given equation in the question (yes or no)?
Yes if the reaction has double arrows.
Do batteries consists of one or more voltaic cells?
Depending on the answer - are they spontaneous (Ecell >0)?
Yes
Spontaneous
Voltage for Dead Battery?(E = x volts)
Ecell = 0V
Formula linking charge (coulomb), current (ampere), and time (seconds).
Q=It
What does Q represent in Formula linking charge, current, and time?
Charge (coulomb) symbolized by Q in equation.
What does I represent in Formula linking charge, current, and time?
Current (ampere) symbolized by I.
Q = It (definition)
The charge transferred, Q, by a passage of a constant current, I, over a specified time interval, t.
Q = nF (definition)
Charge transferred (Q) by a redox reaction in an electrochemical cell.
Equation that relates charge (Q), Faraday’s Constant (F), and the number of electrons (n)
Q = nf
Steps (3) for writing Half Equations
- Write down the ion and the product that will
form at the electrode, with an arrow in
between them.
Cl⁻ → Cl2 - Use coefficients to balance the atoms on
both sides of the equation.
2Cl⁻ → Cl2 - Use electrons to balance the charges on
both sides of the equation.
2Cl⁻ → Cl2 + 2e⁻ (watch out for diatomic
elements).
Affect on (Nerst) Cell Potential when Q decreases and Q increases (Q=product/reactant)
When Q decreases Ecell increases (moving farther away from equilibrium).
When Q increases Ecell decreases (moving closer to equilibrium).
