Pick out incorrect statement about `K_(2)Cr_(2)O_(7)`

Options

A. It oxidizes acidified solution of `H_(2)S` to S
B. It oxidizes KI to `I_(2)`
C. It oxidizes HCl to `Cl_(2)`
D. It gives oxygen, which treated with cold dil. `H_(2)SO_(4)`

Answer

To determine the incorrect statement about \( K_2Cr_2O_7 \) (potassium dichromate), we will analyze each of the provided statements step by step.

### Step 1: Analyze Statement 1
**Statement:** \( K_2Cr_2O_7 \) oxidizes acidified solution of \( H_2S \) to Sulphur.

**Analysis:**
- \( K_2Cr_2O_7 \) is a strong oxidizing agent.
- In an acidified solution, it reacts with \( H_2S \) to oxidize it to sulfur and itself gets reduced.
- The balanced reaction can be written as:
\[ K_2Cr_2O_7 + 3 H_2S + 4 H_2SO_4 \rightarrow K_2SO_4 + Cr_2(SO_4)_3 + 3 S + 7 H_2O \]
- This statement is **correct**.

### Step 2: Analyze Statement 2
**Statement:** \( K_2Cr_2O_7 \) oxidizes \( KI \) to \( I_2 \).

**Analysis:**
- \( K_2Cr_2O_7 \) can oxidize potassium iodide (\( KI \)) to iodine (\( I_2 \)).
- The balanced reaction is:
\[ K_2Cr_2O_7 + 7 H_2SO_4 + 6 KI \rightarrow K_2SO_4 + Cr_2(SO_4)_3 + 3 I_2 + 7 H_2O \]
- This statement is also **correct**.

### Step 3: Analyze Statement 3
**Statement:** \( K_2Cr_2O_7 \) oxidizes \( HCl \) to \( Cl_2 \).

**Analysis:**
- \( K_2Cr_2O_7 \) reacts with hydrochloric acid (\( HCl \)) to produce chlorine gas (\( Cl_2 \)).
- The balanced reaction is:
\[ K_2Cr_2O_7 + 14 HCl \rightarrow 2 CrCl_3 + 2 KCl + 7 H_2O + 3 Cl_2 \]
- This statement is **correct**.

### Step 4: Analyze Statement 4
**Statement:** \( K_2Cr_2O_7 \) gives oxygen when it reacts with cold dilute sulfuric acid.

**Analysis:**
- When \( K_2Cr_2O_7 \) reacts with cold dilute sulfuric acid, it does not release oxygen. Instead, it forms chromium(III) sulfate and does not produce oxygen gas.
- The reaction is:
\[ K_2Cr_2O_7 + 4 H_2SO_4 \rightarrow K_2SO_4 + Cr_2(SO_4)_3 + 2 H_2O \]
- Thus, this statement is **incorrect**.

### Conclusion
The incorrect statement about \( K_2Cr_2O_7 \) is that it gives oxygen when reacting with cold dilute sulfuric acid.

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