A cell constructed by coupling a standard copper electrode and a standard magnesium electrode has EMF to 2.7 volts. If the standard reduction potential of copper electrode is +0.34 volt that of magnesium electrode is:-

Options

A. `+3.04`volts
B. `-3.04` volts
C. `+2.36` volts
D. `-2.36` volts

Explanation

To solve the problem, we need to determine the standard reduction potential of the magnesium electrode based on the information provided. Here’s the step-by-step solution:

### Step 1: Understand the EMF of the Cell
The EMF (Electromotive Force) of the cell is given as 2.7 volts. This value represents the overall potential difference between the two electrodes in the electrochemical cell.

### Step 2: Identify the Cathode and Anode
In the cell constructed with a copper electrode and a magnesium electrode:
- The copper electrode acts as the cathode (where reduction occurs).
- The magnesium electrode acts as the anode (where oxidation occurs).

### Step 3: Write the Formula for Cell EMF
The formula for the EMF of the cell can be expressed as:
\[ E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}} \]

### Step 4: Substitute Known Values
From the problem, we know:
- \( E^\circ_{\text{cell}} = 2.7 \, \text{V} \)
- \( E^\circ_{\text{cathode}} \) (for copper) = +0.34 V

Let \( E^\circ_{\text{anode}} \) (for magnesium) be represented as \( E^\circ_{\text{Mg}} \).

Substituting these values into the formula gives:
\[ 2.7 = 0.34 - E^\circ_{\text{Mg}} \]

### Step 5: Rearrange the Equation
To find \( E^\circ_{\text{Mg}} \), we rearrange the equation:
\[ E^\circ_{\text{Mg}} = 0.34 - 2.7 \]

### Step 6: Calculate the Value
Now, perform the calculation:
\[ E^\circ_{\text{Mg}} = 0.34 - 2.7 = -2.36 \, \text{V} \]

### Conclusion
The standard reduction potential of the magnesium electrode is:
\[ E^\circ_{\text{Mg}} = -2.36 \, \text{V} \]

### Final Answer
The standard reduction potential of the magnesium electrode is **-2.36 V**.

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