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Electrochemistry — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryElectrochemistry3 Marks
Question
Discuss the method to determine electrode potential of copper and zine by using standard hydrogen electrode.
✓

Answer

$\rightarrow $ At a standard temperature of $298K,$ the $\text{EMF}$ of a cell can be measured by pairing the standard hydrogen electrode with the second half cell, constructed by taking the $\text{SHE}$ as the anode $($reference half cell$)$ and the other half cell as the cathode.
$\rightarrow $ standard hydrogen electrode $||$ other half-cell
$\rightarrow $ If the concentrations of the oxidised and the reduced forms of the species in the right hand half$-$cell are unity, then the cell potential is equal to standard electrode potential. $E _{ R }^0$
$E ^{\ominus}= E _{ R }^{\ominus}- E _{ L }^{\ominus}$
As $E _{ L }^{\ominus}$for standard hydrogen electrode is zero.
$E ^{\ominus}= E _{ R }^{\ominus}-0= E _{ R }^{\ominus}$
Electrode potential of copper
$Pt ( s ) \mid H _2(g, 1 \text { bar }) \mid H ^{+}( aq , 1 M ) \| Cu ^{2+} \text { (aq, } 1$
$M ) \mid Cu$
$\rightarrow $ EMF of above cell is $0.34 V$
So,
$E ^0= E _{ R }^0- E _{ L }^0$
$0.34= E _{ Cu ^{+2} \mid Cu }^0-0.0$
$\therefore E _{ Cu }^0{ }^{+2} \text { Cu }$
Electrode potential of $Cu$ is $0.34 V$
Electrode potential of Zinc
$Pt ( s )\left| H _2(g, 1 bar )\right| H ^{+}( aq , 1 M )|| Zn ^{2+}( aq , 1 M ) \mid Zn$
$\rightarrow \text{EMF}$ of above cell is $-0.76 V$
So,
$E ^0= E _{ R }^0- E _{ L }^0$
$-0.76=E_{ Zn ^{+2} \mid Zn }^{ R }-0.0$
$\therefore E _{ Zn^{+2} \mid Zn }^0=-0.76 V$
Electrode potential of Zinc is $-0.76 V$

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