The standard electrode potentials `(E_(M^(+)//M)^(@))` of four metals A, B, C and D are `-1.2V, 0.6V, 0.85 V and -0.76V`, respectively. The sequence of deposition of metals on applying potential is

Options

A. `B gt D gt C gt A`
B. `A gt C gt B gt D`
C. `C gt B gt D gt A`
D. `D gt A gt B gt C`

Answer

To determine the sequence of deposition of metals A, B, C, and D when a potential is applied, we need to analyze their standard electrode potentials (E°). The metals with higher standard electrode potentials will be reduced first and will deposit at the cathode.

### Step-by-Step Solution:

1. **Identify the Standard Electrode Potentials**:
- Metal A: E° = -1.2 V
- Metal B: E° = 0.6 V
- Metal C: E° = 0.85 V
- Metal D: E° = -0.76 V

2. **Rank the Metals by Their Standard Electrode Potentials**:
- The higher the E° value, the stronger the oxidizing agent and the more likely it is to be reduced (deposited).
- Arrange the metals from highest to lowest E°:
- C: 0.85 V
- B: 0.6 V
- D: -0.76 V
- A: -1.2 V

3. **Determine the Sequence of Deposition**:
- The metal with the highest E° (C) will deposit first.
- Next, the metal with the second highest E° (B) will deposit.
- Following that, the metal with the third highest E° (D) will deposit.
- Finally, the metal with the lowest E° (A) will deposit last.

4. **Final Sequence**:
- The sequence of deposition of metals is: **C, B, D, A**.