Understanding the Ethanol Bedside Test Sequence

The bedside test for ethanol involves a specific sequence of steps to reliably detect its presence based on a chemical reaction. This test relies on the formation of an ester, ethyl acetate, which has a distinct fruity smell.

Step 1: Sample Preparation (D)

The procedure begins with the sample. D instructs to place 1 ml of the unknown solution in a test tube. This is the starting point for the analysis.

Step 2: Adding Acetic Acid (A)

Next, 1 ml of acetic acid ($CH_3COOH$) is added to the test tube. Acetic acid is one of the reactants needed for the esterification reaction.

Step 3: Adding Sulfuric Acid Catalyst (E)

Following the acetic acid, 1 drop of concentrated sulfuric acid ($H_2SO_4$) is added. Sulfuric acid serves as a catalyst, significantly speeding up the chemical reaction without being consumed itself.

Step 4: Gentle Heating (B)

The test tube mixture is then heated gently for approximately 1 minute (B). This gentle heating provides the activation energy required for the esterification reaction to occur efficiently.

The core chemical reaction is:

$ CH_3COOH \text{ (Acetic Acid)} + CH_3CH_2OH \text{ (Ethanol)} \xrightarrow{H_2SO_4, \Delta} CH_3COOCH_2CH_3 \text{ (Ethyl Acetate)} + H_2O \text{ (Water)} $

Step 5: Observation of Result (C)

Finally, the result is observed. This involves carefully smelling the vapors produced (wafting towards the nose). C states that a characteristic strong fruity odor confirms a positive test for ethanol. This specific smell is due to the formation of ethyl acetate ($CH_3COOCH_2CH_3$).

The Correct Sequence Explained

Putting these steps together in the correct order is crucial for the test's success:

1. D: Start with the unknown solution.
2. A: Add acetic acid.
3. E: Add the sulfuric acid catalyst.
4. B: Heat the mixture gently.
5. C: Observe the characteristic fruity odor.

This sequence, D, A, E, B, C, ensures that the reactants are mixed correctly, the catalyst is present, the reaction is facilitated by heating, and the resulting product (ethyl acetate) can be identified by its smell.