Carbon phosgene , `COCl_2` is prepared by .

Options

A. the combination of `CO` with ` Cl_2` sunlight
B. the action of ` 80%` fuming `H_2SO_4` boiling in `C Cl_4`
C. oxidising `CHCl_3` with `K_2Cr_2 O_7` and ` H_2SO_4`
D. all of the above

Answer

To prepare carbon phosgene (COCl₂), we can follow these steps based on the methods mentioned in the video transcript:

### Step 1: Combination of Carbon Monoxide and Chlorine
- The first method to prepare carbon phosgene is by the direct combination of carbon monoxide (CO) and chlorine gas (Cl₂) in the presence of sunlight.
- The reaction can be represented as:
\[ \text{CO (g)} + \text{Cl}_2 \text{(g)} \xrightarrow{\text{sunlight}} \text{COCl}_2 \text{(g)} \]
- This method is straightforward and involves the direct reaction of the two gases.

### Step 2: Reaction of Fuming Sulfuric Acid with Carbon Tetrachloride
- The second method involves the action of 80% fuming sulfuric acid (H₂SO₄) on carbon tetrachloride (CCl₄) at elevated temperatures.
- The reaction can be represented as:
\[ \text{CCl}_4 + \text{H}_2\text{SO}_4 \rightarrow \text{COCl}_2 + \text{HCl} + \text{S}_2\text{O}_5\text{Cl}_2 \]
- In this reaction, carbon tetrachloride reacts with sulfuric acid to produce carbon phosgene along with other byproducts.

### Step 3: Oxidation of Chloroform
- The third method is the oxidation of chloroform (CHCl₃) using potassium dichromate (K₂Cr₂O₇) and sulfuric acid (H₂SO₄).
- The reaction can be represented as:
\[ \text{CHCl}_3 + \text{K}_2\text{Cr}_2\text{O}_7 + \text{H}_2\text{SO}_4 \rightarrow \text{COCl}_2 + \text{H}_2\text{O} + \text{Cl}_2 \]
- In this case, the nascent oxygen produced from the oxidation reacts with chloroform to form carbon phosgene.

### Conclusion
- All three methods mentioned above are valid for the preparation of carbon phosgene (COCl₂). Therefore, the answer to the question is that carbon phosgene can be prepared by all of the methods listed.

### Final Answer
- **Carbon phosgene (COCl₂) is prepared by:**
1. The combination of CO and Cl₂ in sunlight.
2. The action of 80% fuming H₂SO₄ boiling in CCl₄.
3. Oxidizing CHCl₃ with K₂Cr₂O₇ and H₂SO₄.

Thus, the correct answer is **all of the above**.