Lucas reagent is:

Options

A. Conc. HCl and anhydrous `ZnCl_(2)`
B. Conc. `HNO_(3)` and anhydrous `ZnCl_(2)`
C. Dil. HCl and anhydrous `ZnCl_(2)`
D. Dil. `HNO_(3)` and anhydrous `ZnCl_(2)`

Explanation

**Step-by-Step Solution:**

1. **Definition of Lucas Reagent**: Lucas reagent is a solution used in organic chemistry to differentiate between primary, secondary, and tertiary alcohols. It is composed of anhydrous zinc chloride (ZnCl2) dissolved in concentrated hydrochloric acid (HCl).

2. **Purpose of Lucas Test**: The primary purpose of the Lucas test is to determine the type of alcohol present in a sample. The test exploits the reactivity of alcohols with Lucas reagent, leading to the formation of alkyl chlorides.

3. **Reaction Mechanism**:
- **Primary Alcohols**: When a primary alcohol reacts with Lucas reagent, it forms an alkyl chloride, but the turbidity (cloudiness) appears only after heating. This is because primary alcohols are less reactive and require more time to form the product.
- **Secondary Alcohols**: In the case of secondary alcohols, the reaction also produces alkyl chlorides, but turbidity is observed within about 5 minutes, indicating a moderate reactivity.
- **Tertiary Alcohols**: Tertiary alcohols react very quickly with Lucas reagent, leading to immediate turbidity due to the rapid formation of alkyl chlorides.

4. **Conclusion**: The Lucas test is a valuable qualitative test in organic chemistry for distinguishing between different types of alcohols based on the speed of turbidity formation after the addition of Lucas reagent.

5. **Correct Answer**: The Lucas reagent is anhydrous ZnCl2 in concentrated HCl.

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