Using the data given below:
`E_(Cr_(2)O_(7)^(2-)|Cr^(3+))^(@)=1.33V E_(Cl_(2)|Cl^(-))^(@)=1.36V`
`E_(MnO_(4)^(-)|Mn^(2+))^(@)=1.51V E_(Cr^(3+)|Cr)=-0.74V`
Mark the strongest reducing agent.

Options

A. `Cl^-`
B. `Cr`
C. `Cr^(3+)`
D. `Mn^(2+)`

Explanation

To determine the strongest reducing agent from the given standard reduction potentials, we will follow these steps:

### Step 1: Understand the concept of reducing agents
A reducing agent is a substance that donates electrons in a chemical reaction and gets oxidized in the process. The stronger the reducing agent, the higher its tendency to lose electrons.

### Step 2: Convert reduction potentials to oxidation potentials
To find the strongest reducing agent, we need to convert the given standard reduction potentials (E°) into oxidation potentials. The oxidation potential is simply the negative of the reduction potential.

### Step 3: List the given reduction potentials
We have the following reduction potentials:
1. \( E_{Cr_2O_7^{2-}/Cr^{3+}}^{\circ} = 1.33 \, V \)
2. \( E_{Cl_2/Cl^{-}}^{\circ} = 1.36 \, V \)
3. \( E_{MnO_4^{-}/Mn^{2+}}^{\circ} = 1.51 \, V \)
4. \( E_{Cr^{3+}/Cr}^{\circ} = -0.74 \, V \)

### Step 4: Calculate oxidation potentials
Now, we will calculate the oxidation potentials for each half-reaction:
1. For \( Cr_2O_7^{2-}/Cr^{3+} \):
\[ E_{ox} = -E_{red} = -1.33 \, V \]
2. For \( Cl_2/Cl^{-} \):
\[ E_{ox} = -E_{red} = -1.36 \, V \]
3. For \( MnO_4^{-}/Mn^{2+} \):
\[ E_{ox} = -E_{red} = -1.51 \, V \]
4. For \( Cr^{3+}/Cr \):
\[ E_{ox} = -(-0.74 \, V) = 0.74 \, V \]

### Step 5: Compare oxidation potentials
Now we have the following oxidation potentials:
1. \( Cr_2O_7^{2-}/Cr^{3+} \): -1.33 V
2. \( Cl_2/Cl^{-} \): -1.36 V
3. \( MnO_4^{-}/Mn^{2+} \): -1.51 V
4. \( Cr^{3+}/Cr \): 0.74 V

### Step 6: Identify the strongest reducing agent
The strongest reducing agent will have the highest oxidation potential. From our calculations, the oxidation potential of \( Cr^{3+}/Cr \) is 0.74 V, which is the highest among all the calculated values.

### Conclusion
Thus, the strongest reducing agent among the given species is **Chromium (Cr)**.

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