IB Chemistry SL Reactivity 3.2.6 Primary Voltaic Cells

Practise explaining how a spontaneous redox reaction in a primary voltaic cell produces electrical energy. Trace electrons through the external circuit from anode to cathode,…

Exam points

trace electrons from the oxidation anode to the reduction cathode through the wire
explain how salt-bridge ions migrate to maintain electrical neutrality in each half-cell
draw or describe two connected half-cells with electrodes, voltmeter and salt bridge

[Maximum number: 1]

Iron rusts in the presence of oxygen and water. Rusting is a redox process involving several steps that produces hydrated iron(III) oxide, $\mathrm{Fe}_{2} \mathrm{O}_{3} \bullet \mathrm{nH}_{2} \mathrm{O}$ , as the final product. The half-equations involved for the first step of rusting are given below.

Half-equation 1: $\quad \mathrm{Fe}(\mathrm{s}) \rightarrow \mathrm{Fe}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-}$

Half-equation 2: $\quad \mathrm{O}_{2}(\mathrm{aq})+4 \mathrm{e}^{-}+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow 4 \mathrm{OH}^{-}(\mathrm{aq})$

A voltaic cell is made from a half-cell containing a magnesium electrode in a solution of magnesium nitrate and a half-cell containing a silver electrode in a solution of silver(I) nitrate.

Figure for Question 3.2.6—Primary (voltaic) cells question 1 — IB Chemistry SL

Negative electrode (anode):

Positive electrode (cathode):
(ii) Outline one function of the salt bridge.

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3.2.6—Primary (voltaic) cells question 1