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VICChemistryQuick questions
Unit 3: How can design and innovation help to optimise chemical processes?
Quick questions on Redox reactions and the electrochemical series: VCE Chemistry Unit 3
10short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is redox in terms of electrons?Show answer
A redox reaction involves the transfer of electrons between species.
What is half-equations?Show answer
A half-equation shows just one half of the redox process (the oxidation OR the reduction), including the electrons transferred. Half-equations must be balanced for atoms and charge.
What is combining half-equations into an overall ionic equation?Show answer
1. Multiply each half-equation so the number of electrons in oxidation equals the number in reduction. 2. Add the two half-equations.
What is the electrochemical series?Show answer
The electrochemical series (in your VCAA data book) lists half-equations written as reductions with their standard electrode potentials (E°) measured at 25°C, 1 mol L^-1 (or 1 atm for gases), against the standard hydrogen electrode (SHE = 0.00 V).
What is predicting spontaneity?Show answer
To check whether a proposed reaction is spontaneous:
What is forgetting to balance electrons before adding half-equations?Show answer
If oxidation gives 2e^- and reduction needs 3e^-, multiply oxidation by 3 and reduction by 2 so each contributes 6e^-.
What is reversing E° when reversing a half-equation?Show answer
Do not change the sign of E° when writing oxidation instead of reduction in the overall equation. For the cell EMF formula, always use the reduction potential as listed.
What is using the reactivity series in place of the electrochemical series?Show answer
The reactivity series is a rough ordering for metals only. The electrochemical series is the quantitative, full version. VCAA expects the quantitative argument.
What is confusing oxidant/oxidised and reductant/reduced?Show answer
The oxidant causes oxidation of others while itself being reduced. The reductant causes reduction of others while itself being oxidised. Use the data book conventions to stay consistent.
What is predicting spontaneity from concentration or surface area?Show answer
Standard electrode potentials assume 1 mol L^-1 and 25°C. Real systems shift, but VCAA Unit 3 problems assume standard conditions unless told otherwise.