Redox Basics
What is oxidation?
Loss of electrons.
What is an electrochemical cell?
A device that converts chemical energy into electrical energy.
What does ΔG represent?
Gibbs free energy change of a reaction.
Write the equation for calculating cell potential.
E°cell = E°cathode − E°anode
Given:
E°Ag = +0.80 V
E°Cu = +0.34 V
Calculate E°cell.
0.80 − 0.34 = 0.46 V
What is reduction?
Gain of electrons.
Electrons flow from which electrode to which?
Anode → Cathode
What does ΔG < 0 mean?
The reaction is spontaneous.
What does n represent in ΔG = −nFE°?
Number of electrons transferred
Given:
E°cell = 1.10 V
n = 2
Find ΔG°.
ΔG° ≈ −212 kJ/mol
In a redox reaction, what is the oxidizing agent?
The substance that accepts electrons and gets reduced.
What is the function of the salt bridge?
Maintains charge balance by allowing ions to move.
What does E°cell > 0 indicate?
The reaction is spontaneous.
What constant does F represent?
Faraday constant (96485 C/mol)
Given:
n = 2
E°cell = 0.50 V
Question:
Find ΔG°.
Use:
ΔG° = −nFE°
ΔG° = −(2)(96485)(0.50)
ΔG° ≈ −96.5 kJ/mol
In an electrochemical cell, where does oxidation occur?
At the anode.
What type of cell produces electricity from a spontaneous reaction?
Galvanic (Voltaic) cell
What equation relates Gibbs free energy and cell potential?
ΔG° = −nFE°
What equation relates Gibbs free energy and equilibrium constant?
ΔG° = −RT lnK
Find the cell potential.
Given:
E°(Fe³⁺/Fe²⁺) = +0.77 V
E°(Zn²⁺/Zn) = −0.76 V
Question:
Calculate E°cell.
E°cell = 0.77 − (−0.76)
Identify the oxidizing agent in this reaction:
Zn + Cu²⁺ → Zn²⁺ + Cu
Cu²⁺
What is the reference electrode used for measuring standard potentials?
Standard Hydrogen Electrode (SHE)
If ΔG is positive, what does this indicate about the reaction?
The reaction is non-spontaneous.
Write the equation relating cell potential and equilibrium constant.
E° = (0.059/n) logK
Given:
n = 3
E°cell = 0.75 V
Question:
Calculate ΔG°.
ΔG° = −nFE°
ΔG° = −(3)(96485)(0.75)
ΔG° ≈ −217 kJ/mol