chapter 5 electrochemistry class 12 chemistry textbook solution
4. Answer the following :
vi. Calculate emf of the following cell at 250C. Zn (s) |Zn2⊕(0.08M)||Cr3⊕(0.1M)|Cr E0
Zn = – 0.76 V, E0 Cr = – 0.74 V (0.0327 V)
Answer:-
\(\text{Given:}\)
\[ E_{\text{Zn}}^\circ = -0.76 \, \text{V}, \, E_{\text{Cr}}^\circ = -0.74 \, \text{V} \]
\(\text{To find: Emf of the cell } (E_{\text{cell}})\)
\(\text{Formulae:}\)
1) \(E_{\text{cell}}^\circ = E_{\text{cathode}}^\circ - E_{\text{anode}}^\circ\)
2) \(E_{\text{cell}} = E_{\text{cell}}^\circ - \frac{0.0592 \, \text{V}}{n} \log_{10} \left[\frac{\text{Product}}{\text{Reactant}}\right]\)
\(\text{Calculation:}\)
\[ 3\text{Zn}_{(s)} \rightarrow 2\text{Cr}_{(0.1 \, \text{M})}^{3+} - 3\text{Zn}_{(0.08 \, \text{M})}^{2+} + \text{Cr}_{(s)} \, (\text{overall reaction}) \]
Using formula (1):
\[ E_{\text{cell}}^\circ = E_{\text{cathode}}^\circ - E_{\text{anode}}^\circ \]
\[ E_{\text{cell}} = E_{\text{Cr}}^\circ - E_{\text{Zn}}^\circ \]
\[ = -0.74 \, \text{V} - (-0.76 \, \text{V}) = 0.02 \, \text{V} \]
Using formula (2):
\[ \text{The cell potential is given by} \]
\[ E_{\text{cell}} = E_{\text{cell}}^\circ - \frac{0.0592 \, \text{V}}{6} \log_{10} \left(\frac{0.08^3}{0.1^2}\right) \]
\[ = 0.02 \, \text{V} + 0.0127 = 0.0327 \, \text{V} \]
The emf of the cell is \(0.0327 \, \text{V}\).
chapter 5 elctrochemistry textbook solution page 118