In the laboratory, chloroform is prepared by which of the following method?

Options

A. By oxidation of isopropyl alcohol with bleaching powder
B. By reduction of carbon tetrachloride with Fe+`H_(2)`O
C. By oxidation of carbon tertrachloride with bleaching powder
D. None of the above

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks for the laboratory method used to prepare chloroform.

2. **Identifying the Reactants:**
The laboratory preparation of chloroform involves the use of bleaching powder, which is chemically known as calcium oxychloride (Ca(OCl)₂).

3. **Reaction with Alcohol:**
The reaction typically involves heating bleaching powder with ethanol (C₂H₅OH) or acetone ((CH₃)₂CO).

4. **Formation of Chlorine Gas:**
When bleaching powder is mixed with water, it releases chlorine gas (Cl₂) and calcium hydroxide (Ca(OH)₂):
\[ \text{Ca(OCl)₂} + \text{H₂O} \rightarrow \text{Ca(OH)₂} + \text{Cl₂} \]

5. **Chlorination of Ethanol:**
Ethanol reacts with chlorine gas to form chloroform through a series of reactions. Initially, ethanol is chlorinated to form acetaldehyde (CH₃CHO) and hydrochloric acid (HCl):
\[ \text{C₂H₅OH} + \text{Cl₂} \rightarrow \text{CH₃CHO} + 2\text{HCl} \]

6. **Further Chlorination:**
The acetaldehyde can undergo further chlorination to form chloroform (CHCl₃):
\[ \text{CH₃CHO} + 3\text{Cl₂} \rightarrow \text{CHCl₃} + 3\text{HCl} \]

7. **Final Reaction with Calcium Hydroxide:**
The chloroform can be obtained by reacting the intermediate products with calcium hydroxide:
\[ \text{CCl₃CHO} + \text{Ca(OH)₂} \rightarrow \text{CHCl₃} + \text{Ca(HCOO)₂} \]

8. **Conclusion:**
Therefore, the correct method for the laboratory preparation of chloroform is by heating a mixture of bleaching powder with ethanol or acetone.

**Final Answer:**
Chloroform is prepared in the laboratory by heating a mixture of bleaching powder with ethanol or acetone.

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