Acetaldehyde and acetylene can be distinguished by :

Options

A. Tollen's reagent
B. Fehling solution
C. Lucas reagent
D. Iodoform test

Explanation

To distinguish between acetaldehyde and acetylene, we can utilize several reagents. Here’s a step-by-step breakdown of the methods:

### Step 1: Understand the Compounds
- **Acetaldehyde (CH₃CHO)**: It is an aliphatic aldehyde.
- **Acetylene (C₂H₂)**: It is a terminal alkyne.

### Step 2: Tollen's Reagent Test
- **Tollen's Reagent**: This reagent is also known as the silver mirror test. It consists of ammoniacal silver nitrate (Ag(NH₃)₂⁺).
- **Reaction**: Acetaldehyde will reduce Tollen's reagent, resulting in the formation of a silver mirror on the test tube's inner surface. Acetylene does not produce a silver mirror.
- **Conclusion**: Acetaldehyde gives a positive Tollen's test, while acetylene does not.

### Step 3: Fehling's Solution Test
- **Fehling's Solution**: This solution contains copper(II) sulfate and sodium potassium tartrate.
- **Reaction**: Acetaldehyde will react with Fehling's solution and reduce it, forming a red precipitate of copper(I) oxide. Acetylene does not react with Fehling's solution.
- **Conclusion**: Acetaldehyde gives a positive Fehling's test, while acetylene does not.

### Step 4: Lucas Reagent Test
- **Lucas Reagent**: This reagent is used to differentiate between primary, secondary, and tertiary alcohols, but it is not applicable for distinguishing between aldehydes and alkynes.
- **Conclusion**: This reagent will not help in distinguishing acetaldehyde from acetylene.

### Step 5: Iodoform Test
- **Iodoform Test**: This test is used to identify methyl ketones and some aldehydes.
- **Reaction**: Acetaldehyde (which has a methyl group adjacent to the carbonyl) will give a positive iodoform test, producing a yellow precipitate of iodoform (CHI₃). Acetylene does not give this test.
- **Conclusion**: Acetaldehyde gives a positive iodoform test, while acetylene does not.

### Final Conclusion:
- **Distinguishing Tests**: Acetaldehyde can be distinguished from acetylene using Tollen's reagent, Fehling's solution, and the iodoform test. Acetylene does not react positively in these tests.