Potential of normal calomel electrode is -0.28 V . The emf of cell obtained by combining Zn and Cu electrodes of a Daniel cell with normal calomel electrodes are 1.083 V and - 0.018 V at `25^@C`. Determine the EMF of Daniel cell.

Answer

To determine the EMF of the Daniel cell, we will follow these steps:

### Step 1: Identify the Standard Electrode Potentials
We are given the following standard electrode potentials:
- Potential of the normal calomel electrode (E°_Calomel) = -0.28 V
- EMF of the cell with Zn electrode (E°_Zn) = 1.083 V
- EMF of the cell with Cu electrode (E°_Cu) = -0.018 V

### Step 2: Calculate the EMF of the Daniel Cell
The EMF of the Daniel cell can be calculated using the formula:
\[ \text{EMF}_{\text{cell}} = E°_{\text{oxidizing electrode}} - E°_{\text{reducing electrode}} \]

In the Daniel cell:
- The oxidizing electrode is Zn (which is oxidized).
- The reducing electrode is the Calomel electrode.

Using the values:
\[ \text{EMF}_{\text{Daniel cell}} = E°_{\text{Zn}} - E°_{\text{Calomel}} \]
\[ \text{EMF}_{\text{Daniel cell}} = 1.083 \, \text{V} - (-0.28 \, \text{V}) \]
\[ \text{EMF}_{\text{Daniel cell}} = 1.083 \, \text{V} + 0.28 \, \text{V} \]
\[ \text{EMF}_{\text{Daniel cell}} = 1.363 \, \text{V} \]

### Step 3: Calculate the EMF for the Copper Electrode
Now, we can also calculate the EMF for the copper electrode:
\[ \text{EMF}_{\text{Cu}} = E°_{\text{Cu}} - E°_{\text{Calomel}} \]
\[ \text{EMF}_{\text{Cu}} = -0.018 \, \text{V} - (-0.28 \, \text{V}) \]
\[ \text{EMF}_{\text{Cu}} = -0.018 \, \text{V} + 0.28 \, \text{V} \]
\[ \text{EMF}_{\text{Cu}} = 0.262 \, \text{V} \]

### Step 4: Combine the EMFs
Finally, to find the total EMF of the Daniel cell, we can add the EMFs calculated:
\[ \text{EMF}_{\text{Daniel cell}} = \text{EMF}_{\text{Zn}} + \text{EMF}_{\text{Cu}} \]
\[ \text{EMF}_{\text{Daniel cell}} = 1.363 \, \text{V} + 0.262 \, \text{V} \]
\[ \text{EMF}_{\text{Daniel cell}} = 1.625 \, \text{V} \]

### Conclusion
Thus, the EMF of the Daniel cell is approximately **1.625 V**.

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