AQA A Level Chemistry 5.4 Electrode Potentials & Electrochemical Cells

These flashcards cover key concepts from the lecture on electrode potentials and electrochemical cells, providing a comprehensive review for exam preparation.

What is an electrochemical cell?

An electrochemical cell generates electricity from spontaneous redox reactions.

What defines a half cell in an electrochemical cell?

A half cell is established when a metal is dipped into a solution of its own ions, creating an equilibrium between the metal and its ions.

What is electrode potential?

Electrode potential is the potential difference established between the rod and the solution due to the equilibrium between a metal and its ions.

What factors influence electrode potential?

The position of equilibrium and hence the electrode potential depends on temperature, pressure of gases, and concentration of reagents.

How is standard electrode potential measured?

Standard electrode potential is measured against a standard hydrogen electrode, which is assigned a value of 0.00 V under standard conditions.

What is the standard condition for measuring electrode potentials?

Standard conditions include ion concentration of 1.00 mol/dm³, a temperature of 298 K, and a pressure of 100 kPa.

What does a positive electrode potential indicate?

A positive electrode potential indicates a substance is likely to undergo reduction.

How is the standard electrode potential for bromine expressed?

The standard electrode potential for bromine is given as Br (l) + 2e ⇌ 2Br (aq) with E = +1.09 V.

What happens in an oxidation process within a half cell?

During oxidation, the species loses electrons and an equilibrium is established that pushes the reaction left.

What is the purpose of a salt bridge in an electrochemical cell?

The salt bridge allows mobile ions to complete the circuit between the two half cells.

What is the conventional representation of a cell made of zinc and copper?

The cell is conventionally represented as Zn (s) | Zn²⁺ (aq) || Cu²⁺ (aq) | Cu (s) with a calculated cell potential of E = +1.10 V.

What distinguishes non-rechargeable cells from rechargeable cells?

Non-rechargeable cells cannot undergo a chemical reaction in reverse while rechargeable cells can be reversed by applying a voltage greater than the cell voltage.

What is a Daniell cell?

A Daniell cell is an early electrochemical cell consisting of a zinc rod in zinc sulfate solution and a copper cylinder in copper sulfate solution.

What are the disadvantages of zinc-carbon cells?

Disadvantages include wear of the zinc casing and corrosive leakage of the electrolyte.

How does a lead-acid battery function?

Lead-acid batteries use lead as the negative electrode and lead(IV) oxide as the positive electrode, generating about 2 V.

What is the benefit of lithium-ion cells compared to NiCad cells?

Lithium-ion cells do not suffer from the 'memory effect' and can be topped up without losing charge.

What are the risks associated with hydrogen fuel cells?

Risks include hydrogen being highly flammable, necessitating thick walled storage and production challenges.

What is the overall reaction for a hydrogen-oxygen fuel cell?

2H₂ (g) + O₂ (g) → 2H₂O (l), with an E value of +1.23 V.

What is the significance of the E value being positive for reactions in electrochemical cells?

A positive E value indicates that the reaction is feasible and likely to occur.

What is the role of a salt bridge in an electrochemical cell?

A salt bridge connects the two half cells and maintains electrical neutrality by allowing the flow of ions.

What is the equation used to calculate the cell potential?

The cell potential can be calculated using the Nernst equation: E = E^ ext{°} - rac{RT}{nF} imes ext{ln}(Q).

What is the difference between an electrolytic cell and a galvanic cell?

An electrolytic cell requires an external voltage to drive a non-spontaneous reaction, while a galvanic cell generates electricity from spontaneous reactions.

What is the significance of the standard electrode potential (
E^ ext{°})?

The significance of standard electrode potential is to determine the feasibility of a redox reaction under standard conditions.

What are primary and secondary cells?

Primary cells can only be used once, while secondary cells are rechargeable and can be used multiple times.