The reason to keep chloroform in dark brown coloured bottles is:

Options

A. To stop its oxidation
B. To stop its decomposition
C. To stop the formation of carbon tetrachloride from it
D. To stop its hydrolysis

Answer

**Step-by-Step Solution:**

1. **Understanding Chloroform**: Chloroform is a chemical compound with the formula CHCl3. It is a colorless liquid that has been widely used as a solvent and in the production of other chemicals.

2. **Oxidation of Chloroform**: Chloroform can undergo oxidation when exposed to air, especially under photochemical conditions (i.e., in the presence of light). This reaction can lead to the formation of phosgene (COCl2), which is a highly toxic gas.

3. **The Role of Light**: Light can accelerate the oxidation process of chloroform. Therefore, exposure to light increases the likelihood of chloroform reacting with oxygen in the air, leading to the formation of harmful byproducts.

4. **Storage in Dark Brown Bottles**: To prevent the oxidation of chloroform and the subsequent formation of phosgene, it is stored in dark brown colored bottles. These bottles block out light, thereby minimizing the risk of photochemical reactions.

5. **Conclusion**: The primary reason for storing chloroform in dark brown bottles is to stop its oxidation, which can lead to the formation of toxic compounds.

**Final Answer**: The reason to keep chloroform in dark brown colored bottles is to stop its oxidation.

---