Electrochemistry — WJEC A-Level Chemistry
In summary: Electrochemistry is a key topic in WJEC A-Level Chemistry. Key exam tip: Always ensure half-equations are balanced for both atoms and charge
Exam Tips for Electrochemistry
- Always ensure half-equations are balanced for both atoms and charge
- Remember that Ecell = E(cathode) - E(anode)
- Practice the specific redox titration calculations involving iodine/thiosulfate and manganate(VII) as these are frequently examined
- Be prepared to explain the function of the salt bridge in electrochemical cells
- Use the provided data tables for standard electrode potentials accurately
Common Mistakes
- Incorrectly identifying the direction of electron flow in cell diagrams
- Errors in balancing complex redox half-equations, particularly with acidified reagents
- Confusing the roles of the anode and cathode in different types of cells
- Failure to use the correct number of significant figures in titration calculations
- Misinterpreting the sign of Ecell in relation to reaction feasibility
Marking Points
- Representation of redox systems using ion/electron half-equations
- Construction of cell diagrams for electrochemical cells
- Calculation of cell EMF and determination of reaction feasibility
- Understanding the role of the standard hydrogen electrode
- Principles and limitations of the hydrogen fuel cell
- Combining half-equations to form stoichiometric redox equations
- Calculations involving redox titrations (e.g., MnO4-/Fe2+, Cr2O72-/Fe2+, Cu2+/I- with S2O32-)
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