Which one is the oxidising agent in the reaction given below
`2CrO_(4)^(2-)+2H^(+)rarrCr_(2)O_(7)^(-2)+H_(2)O`

Options

A. `H^(+)`
B. `Cr_(2)O_(7)^(-2)`
C. `Cr^(++)`
D. None

Answer

To determine the oxidizing agent in the reaction:

\[ 2 \text{CrO}_4^{2-} + 2 \text{H}^+ \rightarrow \text{Cr}_2\text{O}_7^{2-} + \text{H}_2\text{O} \]

we need to analyze the oxidation states of the elements involved in the reaction.

### Step 1: Identify the oxidation states

1. **Chromate ion (\(\text{CrO}_4^{2-}\))**:
- The oxidation state of oxygen is \(-2\).
- Let the oxidation state of chromium be \(x\).
- The equation for the chromate ion is:
\[ x + 4(-2) = -2 \implies x - 8 = -2 \implies x = +6 \]
- Therefore, the oxidation state of chromium in \(\text{CrO}_4^{2-}\) is \(+6\).

2. **Dichromate ion (\(\text{Cr}_2\text{O}_7^{2-}\))**:
- The oxidation state of oxygen is still \(-2\).
- Let the oxidation state of chromium be \(y\).
- The equation for the dichromate ion is:
\[ 2y + 7(-2) = -2 \implies 2y - 14 = -2 \implies 2y = 12 \implies y = +6 \]
- Therefore, the oxidation state of chromium in \(\text{Cr}_2\text{O}_7^{2-}\) is also \(+6\).

3. **Hydrogen ions (\(\text{H}^+\))**:
- The oxidation state of hydrogen is \(+1\).

4. **Water (\(\text{H}_2\text{O}\))**:
- The oxidation state of hydrogen is \(+1\) and oxygen is \(-2\).

### Step 2: Analyze the changes in oxidation states

- In this reaction, the oxidation state of chromium does not change:
- From \(\text{CrO}_4^{2-}\) (Cr is +6) to \(\text{Cr}_2\text{O}_7^{2-}\) (Cr is still +6).
- The oxidation state of hydrogen also does not change:
- From \(\text{H}^+\) (H is +1) to \(\text{H}_2\text{O}\) (H is still +1).

### Step 3: Conclusion

Since there is no change in the oxidation states of chromium or hydrogen, there is no oxidation or reduction occurring in this reaction. Therefore, there is no oxidizing agent present.

### Final Answer
The correct option is **none**.

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