CAIE A Level Chemistry 9701 · Electrochemistry

Electrochemistry: describe question

Describe5 marksStandard

A student sets up a simple cell using the two half-cells described below.

Half-cell 1: a silver electrode in contact with AgX+\ce{Ag+} ions, AgX+(aq)+eX−→Ag(s)\ce{Ag+(aq) + e- -> Ag(s)}

Half-cell 2: a copper electrode in contact with CuX2+\ce{Cu^2+} ions, CuX2+(aq)+2 eX−→Cu(s)\ce{Cu^2+(aq) + 2e- -> Cu(s)}

The standard electrode potentials are:

E⊖(AgX+/Ag)=+0.80 VE^\ominus(\ce{Ag+/Ag}) = +0.80\ \text{V}

E⊖(CuX2+/Cu)=+0.34 VE^\ominus(\ce{Cu^2+/Cu}) = +0.34\ \text{V}

Describe how the student can use these standard electrode potentials to deduce the polarity of each electrode and the direction of electron flow in the external circuit of this cell. Include in your answer which electrode is the positive electrode and which is the negative electrode, and state the direction of electron flow.

0 words · 5 marks

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5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.

Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.

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