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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

→ At a standard temperature of 298K, the EMF of a cell can be measured by pairing the standard hydrogen electrode with the second half cell, constructed by taking the SHE as the anode (reference half cell) and the other half cell as the cathode.
→ standard hydrogen electrode || other half-cell
→ 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
$
\begin{array}{l}
Pt ( s ) \mid H _2(g, 1 \text { bar }) \mid H ^{+}( aq , 1 M ) \| Cu ^{2+} \text { (aq, } 1 \\
M ) \mid Cu
\end{array}
$
→ EMF of above cell is 0.34 V
So,
$
\begin{array}{l}
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 }
\end{array}
$
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
$
→ EMF of above cell is -0.76 V$
So,
$
\begin{array}{l}
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 \\
\end{array}
$
Electrode potential of Zinc is -0.76 V

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