sic","front":"What is the function of a salt bridge in an electrochemical cell?","back":"

Connects the circuit
Allows ions to flow to balance charge buildup

","points":2,"mcqOptions":[{"text":"

Connects the circuit
Allows ions to flow to balance charge buildup

","correct":true,"explanation":"A salt bridge completes the circuit by permitting ion migration between half-cells. This prevents charge separation, which would otherwise stop electron flow through the external circuit."},{"text":"

Connects the electrodes
Allows electrons to flow to balance charge buildup

","correct":false,"explanation":"Electrons travel through the external wire rather than through the salt bridge. The bridge completes the circuit by allowing ions to migrate and counter charge buildup in each half-cell."},{"text":"

Increases the cell voltage
Supplies reactive ions to drive the redox reaction

","correct":false,"explanation":"The salt bridge neither increases voltage nor supplies reactants for the redox reaction. It permits ion movement to maintain electrical neutrality and complete the circuit."},{"text":"

Completes the electron pathway
Allows solvent to flow to equalise solution volumes

","correct":false,"explanation":"The electron pathway is the external wire, while equalising solution volumes is not the salt bridge’s role. It allows ions to flow, preventing charge buildup."}]},{"id":"0cb89f9b-95f7-49cc-9f54-a52cdffd66d1","cardType":"basic","front":"Why is potassium nitrate ($\text{KNO}_3$) used as a salt bridge?","back":"It is an unreactive ionic compound.","points":1,"mcqOptions":[{"text":"It is an unreactive ionic compound.","correct":true,"explanation":"Potassium nitrate provides mobile ions but ordinarily does not react with the electrodes, electrolytes or products. It can therefore carry charge without interfering with the cell reaction."},{"text":"It is a reactive ionic compound.","correct":false,"explanation":"A reactive ionic compound could participate in side reactions and alter the measured cell potential. Potassium nitrate is suitable because it is an unreactive ionic compound."},{"text":"It is an unreactive covalent compound.","correct":false,"explanation":"Potassium nitrate consists of potassium and nitrate ions, not covalent molecules. Its unreactive ions remain mobile in solution, allowing the salt bridge to conduct charge."},{"text":"It is a strongly reducing ionic compound.","correct":false,"explanation":"A strong reducing agent would react with oxidising species and interfere with the cell reaction. Potassium nitrate is used because it is an unreactive ionic compound."}]},{"id":"e4e0dc27-4565-41f4-90c5-ce89f22b9c52","cardType":"basic","front":"Why is a high resistance voltmeter used when measuring cell EMF?","back":"To ensure near-zero current flows, preventing changes in ion concentration.","points":2,"mcqOptions":[{"text":"To ensure near-zero current flows, preventing changes in ion concentration.","correct":true,"explanation":"A high resistance draws negligible current, so the cell reaction proceeds insignificantly during measurement. Ion concentrations therefore remain effectively unchanged, giving the cell EMF accurately."},{"text":"To ensure a large current flows, producing a measurable change in ion concentration.","correct":false,"explanation":"A large current would drive the cell reaction rapidly and change ion concentrations, causing the potential to vary. High resistance instead ensures that near-zero current flows."},{"text":"To ensure constant current flows, preventing changes i

Electrode potentials and cells (A-level only)

Electrode potentials and cells (A-level only) Flashcards

Electrode potentials and cells (A-level only)

Electrode potentials and cells (A-level only) Flashcards