electrode potentials and electrochemical cells Flashcards
What happens when electrons move?
You get electricity
In an electrochemical cell, how many reactions occur?
ALWAYS 2 REACTIONS - REDOX
What is the difference between anode and cathode?
Anode = positive = oxidation; Cathode = negative = reduction
What is the relationship between electrode potential and electromotive force?
They are the same thing - E°
What is established when a rod of metal is dipped into a solution of its own ions?
An equilibrium
What is a half-cell?
A half-cell is formed when a metal is dipped into a solution of its own ions
What are the components of an electrochemical cell?
- 2 different metals
- Both dipped in salt solutions of their own ions
- Connected by a wire (the external circuit)
- Circuit completed by a salt bridge
What is the purpose of a salt bridge in an electrochemical cell?
It allows ions to flow through and balance the charges to maintain neutrality
Why are salt bridges used instead of a piece of wire?
To avoid further metal/ion potentials in the circuit
What happens in a zinc/copper electrochemical cell?
- Zinc loses electrons more easily than copper
- Zinc is oxidized
- Copper is reduced
What occurs when the voltmeter is removed from the electrochemical cell?
Electrons flow from zinc to copper, causing zinc to dissolve and copper to be deposited
What is the standard electrode potential (E°)?
The voltage measured under standard conditions when the half-cell is connected to a standard hydrogen electrode
What does a more negative electrode potential indicate?
Easy to oxidise, better reducing agent
What are standard conditions for measuring electrode potential?
- Concentration of 1.00 mol dm⁻³
- Temperature of 298K (25°C)
- Pressure of 100kPa
What does a vertical solid line represent in cell representation?
A phase boundary
What does a double vertical line represent in cell representation?
A salt bridge
What is the electrochemical series?
A list of standard electrode potentials for electrochemical half-cells
How do you calculate standard cell potentials?
E°cell = E°reduced - E°oxidised
What indicates a feasible redox reaction using standard electrode potentials?
A positive value after calculation
What is the outcome of the reaction Fe³⁺(aq) + Cl⁻(aq) → Fe²⁺(aq) + ½ Cl₂(aq)?
Not feasible, E°cell = -0.59
What defines a rechargeable battery?
Can be recharged by reversing the cell reactions
What is the composition of a lithium-ion rechargeable battery?
- Positive electrode: lithium cobalt oxide (LiCoO₂)
- Negative electrode: carbon
What is the overall reaction in an alkaline hydrogen-oxygen fuel cell?
2H₂(g) + O₂(g) → 2H₂O(g) with EMF = 1.23 V
What are the benefits of fuel cells?
- More efficient
- Only waste product is water
- No CO₂ emissions from the cell itself
