Maharashtra BoardEnglish MediumSTD 12 ScienceChemistryElectrochemistry3 Marks
Question
What are the conventions used to write galvanic cell or cell diagram $($cell formula$) ?$
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Answer
A galvanic cell or voltaic cell is represented by a short notation or diagram which includes electrodes, aqueous solutions of ions and other species that may or may not involve in the cell reaction.
The following conventions are used to represent the cell or write the cell notation :
$(1)$ The metal electrodes or the inert electrodes like platinum are placed at the ends of the cell formula.
$(2)$ The galvanic cell consists of two half cells or electrodes. The electrode on the extreme left hand side is anode where oxidation takes place and it carries negative $(-)$ charge while extreme right hand electrode is cathode where reduction takes place and it carries positive $(+)$ charge.
$(3)$ The gases or insoluble substances are placed in the interior positions adjacent to the metal electrode.
$(4)$ A single vertical line is written between two phases like solid electrode and aqueous solution containing ions.
$(5)$ A double vertical line is drawn between two solutions of two electrodes which indicates a salt bridge connecting them electrically.
$(6)$ The concentration of solutions or ions or pressures of gases are written in brackets along with the substances in the cell.
$(7)$ Different ions in the same solution are separated by a comma.
$\text { E.g. } Fe _{( aq )}^{3+}, Fe _{( aq )}^{2+}\left| Pt ; Ag _{( aq )}^{+}(1 M )\right| Ag _{( s )}$
$(8)$ Examples of electrochemical cells :
$(i)$ Daniel cell is represented as,
$Zn _{( s )}\left|\begin{array}{l} Zn _{\text {(aq)}}^{2+} \\ 1 M \end{array}\right|\left|\begin{array}{l} Cu _{\text {(aq) }}^{2+} \\ 1 M \end{array}\right| Zn _{( s )}$
$(ii) \ \left. Pt \left| H _{2( g )}(1 atm )\right| \begin{gathered} H _{( aq )}^{+} \\ 1 M \end{gathered}|| \begin{gathered} Ag _{( aq )}^{+} \\ 1 M \end{gathered} \right\rvert\, Ag _{( s )}$
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