The standard `E_(red)^(@)`Values if A, B and C are `+ 0.68V`, -`0.76V`, `-0.50V` respectively.
The order of their reducing power is :

Options

A. AgtBgtC
B. AgtCgtB
C. CgtBgtA
D. BgtCgtA

Explanation

To determine the order of reducing power of substances A, B, and C based on their standard reduction potentials, we can follow these steps:

### Step 1: Understand the Standard Reduction Potentials
The standard reduction potentials (E°) for the substances are given as follows:
- A: +0.68 V
- B: -0.76 V
- C: -0.50 V

### Step 2: Convert Reduction Potentials to Oxidation Potentials
The oxidation potential is the negative of the reduction potential. Therefore, we can calculate the oxidation potentials for each substance:
- For A: E°(oxidation) = -E°(reduction) = -0.68 V
- For B: E°(oxidation) = -E°(reduction) = +0.76 V
- For C: E°(oxidation) = -E°(reduction) = +0.50 V

### Step 3: Compare the Oxidation Potentials
Now we compare the oxidation potentials:
- A: -0.68 V
- B: +0.76 V
- C: +0.50 V

### Step 4: Determine Reducing Power
The reducing power of a substance is directly related to its oxidation potential. A higher oxidation potential indicates a stronger reducing agent. Thus, we can rank the substances based on their oxidation potentials:
1. B (+0.76 V) - strongest reducing agent
2. C (+0.50 V) - moderate reducing agent
3. A (-0.68 V) - weakest reducing agent

### Step 5: Final Order of Reducing Power
Based on the comparison, the order of reducing power from strongest to weakest is:
**B > C > A**