Chromium has the lowest oxidation state in

Options

A. chromium sulphate
B. chromium trioxide
C. potassium chromate
D. potassium dichromate.

Answer

To determine the lowest oxidation state of chromium among the given compounds, we will analyze the oxidation states in each compound step by step.

### Step 1: Analyze Chromium Sulfate (Cr2(SO4)3)
1. **Assume the oxidation state of chromium (Cr) as X.**
2. The sulfate ion (SO4) has a charge of -2. Since there are 3 sulfate ions, the total charge contributed by sulfate is -6.
3. The equation becomes:
\[ 2X + (-6) = 0 \]
4. Solving for X:
\[ 2X = 6 \implies X = +3 \]
5. **Oxidation state of Cr in chromium sulfate is +3.**

### Step 2: Analyze Chromium Trioxide (CrO3)
1. **Assume the oxidation state of chromium (Cr) as X.**
2. Oxygen has an oxidation state of -2. There are 3 oxygen atoms contributing a total of -6.
3. The equation becomes:
\[ X + (-6) = 0 \]
4. Solving for X:
\[ X = +6 \]
5. **Oxidation state of Cr in chromium trioxide is +6.**

### Step 3: Analyze Potassium Chromate (K2CrO4)
1. **Assume the oxidation state of chromium (Cr) as X.**
2. The potassium ion (K) has a charge of +1. There are 2 potassium ions contributing a total of +2.
3. The chromate ion (CrO4) has a charge of -2.
4. The equation becomes:
\[ 2 + X + (-8) = 0 \quad (\text{since } -2 \times 4 = -8) \]
5. Solving for X:
\[ X - 6 = 0 \implies X = +6 \]
6. **Oxidation state of Cr in potassium chromate is +6.**

### Step 4: Analyze Potassium Dichromate (K2Cr2O7)
1. **Assume the oxidation state of chromium (Cr) as X.**
2. The potassium ion (K) has a charge of +1. There are 2 potassium ions contributing a total of +2.
3. The dichromate ion (Cr2O7) has a charge of -2.
4. The equation becomes:
\[ 2 + 2X + (-14) = 0 \quad (\text{since } -2 \times 7 = -14) \]
5. Solving for X:
\[ 2X - 12 = 0 \implies 2X = 12 \implies X = +6 \]
6. **Oxidation state of Cr in potassium dichromate is +6.**

### Conclusion
After analyzing all four compounds, we find:
- Chromium sulfate: +3
- Chromium trioxide: +6
- Potassium chromate: +6
- Potassium dichromate: +6

The lowest oxidation state of chromium is found in **chromium sulfate (Cr2(SO4)3), which is +3.**