Question

The standard electrode potential of zinc electrode is \(-0.76\,V\) and that of copper electrode is \(+0.34\,V\). The standard EMF of the Daniell cell is:

• A. \(0.42\,V\)
• B. \(1.10\,V\)
• C. \(0.76\,V\)
• D. \(1.52\,V\)

Hint:

In galvanic cells: \[ E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}} \] Always subtract oxidation electrode potential from reduction electrode potential.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
A Daniell cell is a classic electrochemical galvanic cell that converts spontaneous chemical energy from a redox reaction into electrical energy. It consists of a zinc metal strip dipping into a zinc sulfate solution (the anode half-cell) and a copper metal strip dipping into a copper sulfate solution (the cathode half-cell). The electromotive force (EMF) or standard cell potential ($E^\circ_{\text{cell}}$) measures the voltage difference between these two electrodes under standard conditions.
Step 2: Key Formula or Approach:
According to IUPAC conventions, standard electrode potentials are always reported as standard reduction potentials. The standard EMF of a cell is calculated by subtracting the standard reduction potential of the anode from that of the cathode: $$ E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}} $$ Let's identify our electrodes based on their given standard reduction potentials: - The electrode with the higher reduction potential undergoes reduction and acts as the Cathode (Copper: $E^\circ_{\text{Cu}^{2+}/\text{Cu}} = +0.34\text{ V}$). - The electrode with the lower reduction potential undergoes oxidation and acts as the Anode (Zinc: $E^\circ_{\text{Zn}^{2+}/\text{Zn}} = -0.76\text{ V}$).
Step 3: Detailed Explanation:
Let's substitute our specific electrode values directly into the standard cell potential formula: $$ E^\circ_{\text{cell}} = E^\circ_{\text{Cu}^{2+}/\text{Cu}} - E^\circ_{\text{Zn}^{2+}/\text{Zn}} $$ $$ E^\circ_{\text{cell}} = (+0.34\text{ V}) - (-0.76\text{ V}) $$ When subtracting a negative number, the signs combine to perform an addition: $$ E^\circ_{\text{cell}} = 0.34\text{ V} + 0.76\text{ V} $$ $$ E^\circ_{\text{cell}} = 1.10\text{ V} $$ The standard EMF calculated for the Daniell cell is $+1.10\text{ V}$. This matches option (B).
Step 4: Final Answer:
The standard EMF of the Daniell cell is 1.10 V.