The pair of the compounds in which both the metals are in the highest possible oxidation state is,

Options

A. `MnO_(2),FeCl_(3)`
B. `MnO_(4)^(-), CrO_(2)Cl_(2)`
C. `MnCl_(2), CrCl_(3)`
D. `[NiCl_(4)]^(2-), [CoCl_(4)]^(-)`

Explanation

To determine the pair of compounds in which both metals are in their highest possible oxidation states, we will analyze the oxidation states of the metals in each option given.

### Step-by-Step Solution:

1. **Identify the Compounds:**
Let's consider the compounds provided in the options. The compounds mentioned are:
- A: MnO2 and FeCl3
- B: MnO4^- and CrO2Cl2
- C: MnO and NiF2
- D: CoCl3 and NiO

2. **Calculate the Oxidation State of Manganese in MnO2:**
- In MnO2, the oxidation state of oxygen (O) is -2.
- Let the oxidation state of manganese (Mn) be X.
- The equation is:
\[ X + 2(-2) = 0 \implies X - 4 = 0 \implies X = +4 \]
- The highest oxidation state of manganese is +7 (in MnO4^-), so this is not the highest oxidation state.

3. **Calculate the Oxidation State of Iron in FeCl3:**
- In FeCl3, the oxidation state of chlorine (Cl) is -1.
- Let the oxidation state of iron (Fe) be Y.
- The equation is:
\[ Y + 3(-1) = 0 \implies Y - 3 = 0 \implies Y = +3 \]
- The highest oxidation state of iron is +6 (in Fe2O3), so this is not the highest oxidation state.

4. **Calculate the Oxidation State of Manganese in MnO4^-:**
- In MnO4^-, the oxidation state of oxygen is -2.
- Let the oxidation state of manganese be A.
- The equation is:
\[ A + 4(-2) = -1 \implies A - 8 = -1 \implies A = +7 \]
- This is the highest oxidation state of manganese.

5. **Calculate the Oxidation State of Chromium in CrO2Cl2:**
- In CrO2Cl2, the oxidation state of oxygen is -2 and chlorine is -1.
- Let the oxidation state of chromium be B.
- The equation is:
\[ B + 2(-2) + 2(-1) = 0 \implies B - 4 - 2 = 0 \implies B = +6 \]
- This is the highest oxidation state of chromium.

6. **Conclusion:**
- From the calculations, we find:
- In option A: Mn is +4, Fe is +3 (not highest)
- In option B: Mn is +7, Cr is +6 (both highest)
- In option C: Mn is +2, Ni is +2 (not highest)
- In option D: Co is +3, Ni is +2 (not highest)
- Therefore, the correct answer is **Option B: MnO4^- and CrO2Cl2**, where both metals are in their highest oxidation states.