Back to the full dot-point answer
QLDChemistryQuick questions
Unit 3: Equilibrium, acids and redox reactions
Quick questions on Galvanic cells and standard cell potentials (QCE Chemistry Unit 3)
15short 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 what a galvanic cell is?Show answer
A galvanic (voltaic) cell converts the chemical energy of a spontaneous redox reaction into electrical energy. The defining trick is to physically separate the oxidation and reduction half-reactions into two half-cells, forcing the electrons to travel through an external wire rather than transferring directly. The current in the wire can do useful work.
What is anode and cathode?Show answer
The two electrodes are named after the half-reaction occurring at them, regardless of cell type.
What is using the standard reduction potential table?Show answer
The table lists half-reactions written as reductions, with associated E0 values. Highly positive E0 means the species is a strong oxidising agent (readily reduced). Highly negative E0 means the species is a strong reducing agent (readily oxidised; the reverse direction is favoured).
What is worked cell potential calculations?Show answer
Daniell cell (Zn/Cu). E0(Cu2+/Cu) = +0.34 V; E0(Zn2+/Zn) = -0.76 V.
What is cell diagram notation?Show answer
The conventional shorthand for a galvanic cell, used in QCAA EA and IA1:
What is role of the salt bridge in detail?Show answer
1. Zn -> Zn2+ + 2 e- proceeds initially. 2. Zn2+ accumulates in the anode compartment (positive charge build-up).
What is predicting spontaneity from the table?Show answer
The reduction potential table is a kind of "redox priority list". The species higher in the table (more positive E0) wins as the oxidising agent; the species lower (more negative E0) loses electrons.
What is connecting back to equilibrium?Show answer
A galvanic cell delivers current until equilibrium is reached. The reaction proceeds in the spontaneous direction, but the consequent change in ion concentrations (Zn2+ rises, Cu2+ falls) shifts the actual cell potential toward zero. When the cell is fully discharged, the half-cells are at electrochemical equilibrium and the voltage is zero. This is the chemistry of a flat battery.
What is daniell cell?Show answer
E0(Cu2+/Cu) = +0.34 V; E0(Zn2+/Zn) = -0.76 V.
What is ag/Cu cell?Show answer
E0(Ag+/Ag) = +0.80 V; E0(Cu2+/Cu) = +0.34 V.
What is sn/Ag cell?Show answer
E0(Ag+/Ag) = +0.80 V; E0(Sn2+/Sn) = -0.14 V.
What is calling the anode positive in a galvanic cell?Show answer
It is negative. The convention flips in electrolytic cells.
What is computing E0 cell as E0 + E0?Show answer
Subtract, not add. Both E0 values are taken from the table as reductions.
What is forgetting to use the table values as-is?Show answer
Do not flip the sign of E0(anode) before subtracting; the subtraction handles the reversal.
What is confusing the salt bridge with the wire?Show answer
Wire carries electrons (in the external circuit). Salt bridge carries ions (between the half-cells). Different particles, different paths.