Electrode Potentials Flashcards

Interactive active recall cards for electrochemical cells, electrode potentials, cell notation, and batteries.

SHE & Cell Notation: read all 6 questions and answers

What is the Standard Hydrogen Electrode (SHE)?
A reference electrode assigned a potential of 0.00 V, used to measure standard electrode potentials of other half-cells.
State the standard conditions required for the Standard Hydrogen Electrode.
Temperature of 298 K, pressure of 100 kPa for H₂ gas, and concentration of 1.00 mol dm⁻³ for H⁺ ions.
Why is a platinum electrode used in standard reference electrodes?
Platinum is inert, conducts electricity, and provides a catalytic surface for electron transfer between hydrogen gas and H⁺ ions.
State the cell notation convention for representing electrochemical cells.
Write the more negative electrode (oxidation) on the left and the more positive electrode (reduction) on the right. Phase boundaries are | and salt bridges are ||.
What does a double vertical line (||) represent in cell notation?
A salt bridge, which completes the circuit by allowing ions to flow between the two half-cells.
What is the purpose of a salt bridge in an electrochemical cell?
It completes the electrical circuit and maintains electrical neutrality by allowing the transfer of ions without mixing the solutions.

Electrochemical Series & Feasibility: read all 6 questions and answers

State the formula to calculate standard cell EMF (\(E^{\ominus}_{\text{cell}}\)).
\(E^{\ominus}_{\text{cell}} = E^{\ominus}(\text{RHS}) - E^{\ominus}(\text{LHS})\) or \(E^{\ominus}(\text{reduced}) - E^{\ominus}(\text{oxidised})\).
What does a positive standard electrode potential (\(E^{\ominus}\)) tell you about a species?
The species on the left-hand side of the half-equation is a strong oxidising agent (readily gains electrons and undergoes reduction).
What does a negative standard electrode potential (\(E^{\ominus}\)) tell you about a species?
The species on the right-hand side of the half-equation is a strong reducing agent (readily loses electrons and undergoes oxidation).
In which direction do electrons flow in the external circuit of a cell?
From the more negative electrode (LHS / anode / oxidation site) to the more positive electrode (RHS / cathode / reduction site).
How do you predict whether a redox reaction is thermodynamically feasible?
A reaction is feasible if the overall cell EMF (\(E^{\ominus}_{\text{cell}}\)) is positive.
Why might a thermodynamically feasible redox reaction not occur in practice?
The reaction may have a very high activation energy (resulting in an extremely slow rate) or standard conditions are not maintained.

Batteries & Fuel Cells: read all 6 questions and answers

What is a rechargeable battery?
A cell in which the electrochemical reaction is reversible by applying an external electrical current in the opposite direction.
Give a common example of a rechargeable cell used in portable electronics.
The lithium-ion cell, which contains a lithium cobalt oxide electrode and a graphite electrode.
What is a fuel cell?
An electrochemical cell that generates electricity continuously by reacting a fuel (e.g. hydrogen) with an oxidant (e.g. oxygen) supplied from outside.
Write the half-equation at the anode of an alkaline hydrogen-oxygen fuel cell.
H₂ + 2OH⁻ → 2H₂O + 2e⁻.
Write the half-equation at the cathode of an alkaline hydrogen-oxygen fuel cell.
O₂ + 2H₂O + 4e⁻ → 4OH⁻.
Write the overall reaction in a hydrogen-oxygen fuel cell.
2H₂ + O₂ → 2H₂O.