Laboratory Report: Acid-Base Extraction

Abstract

In this experiment, an Acid-Base extraction was performed on a mixture containing the compounds: Benzoic Acid, p-Nitroaniline, and neutral Azobenzene. After the process was completed, three separate extracts were collected (Acidic, Basic, and an Organic). Through vacuum filtration, a 76.54% yield of Benzoic Acid was collected from the Acidic extract, and a 87.69% yield from the Basic Extract. The Organic extract, through distillation and evaporation, produced a 82.39 % yield of Azobenzene. The experimental melting ranges were recorded for each compound and were within the satisfactory ranges of a pure sample.

Introduction

Extraction techniques are commonly used to separate and purify substances from mixtures. These techniques are based on the principles of chromatography, where components in a mixture exhibit varying affinities for different phases. Successful extraction relies on the ability to distribute the components between two immiscible phases, with one phase moving while the other remains stationary.

In this experiment, we utilized liquid-liquid extraction, a method in which the original liquid contains dissolved organic material, and the extracting liquid is immiscible with the original.

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This immiscibility allows for mixing, where the extracting liquid reacts with its target compound, forming a conjugate acid or base that is insoluble in the organic layer. This physically separates it from the organic solution, allowing for decantation. Our specific extraction involved an organic mixture containing acidic Benzoic Acid, basic p-Nitroaniline, and neutral Azobenzene in a Dichloromethane solution.

The extraction process included the following steps:

1. Extraction of the acidic compound (Benzoic Acid) using a basic solution of Sodium Hydroxide to create its conjugate base.
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2. Neutralization of the conjugate base with HCl to regenerate the original acidic compound, followed by vacuum filtration and collection.
3. Extraction of the basic compound (p-Nitroaniline) using Hydrochloric Acid, followed by neutralization with Sodium Hydroxide.
4. The resulting organic solution contains the neutral compound (Azobenzene) and water.
5. Water removal by absorption with anhydrous sodium sulfate, followed by filtration.
6. Collection of Azobenzene through the process of simple distillation and evaporation.

This extraction method allowed us to separate and collect the individual components of the mixture for further analysis.

Experimental Procedure

The following steps were followed to perform the Acid-Base extraction:

1. Weighed and recorded the mass of the mixture containing Benzoic Acid, p-Nitroaniline, and Azobenzene.
2. Added Dichloromethane to the mixture to dissolve the compounds.
3. Separated the organic layer from any insoluble impurities.
4. Prepared a basic solution of Sodium Hydroxide to extract the acidic component (Benzoic Acid).
5. Added the basic solution to the organic mixture and thoroughly mixed it.
6. Allowed the layers to separate, then carefully collected the aqueous (basic) layer.
7. Neutralized the aqueous layer with Hydrochloric Acid until it became slightly acidic, regenerating Benzoic Acid.
8. Performed vacuum filtration to collect the Benzoic Acid crystals.
9. Weighed and recorded the mass of the collected Benzoic Acid.
10. Repeated the above steps for the basic component (p-Nitroaniline), using Hydrochloric Acid for extraction and Sodium Hydroxide for neutralization.
11. Combined the remaining organic solution, containing Azobenzene and water, in a distillation apparatus.
12. Performed simple distillation to separate Azobenzene from water.
13. Collected and recorded the mass of the Azobenzene obtained.
14. Measured the melting points of the collected Benzoic Acid, p-Nitroaniline, and Azobenzene samples.

Results

The experimental results are summarized in the following table:

The melting point ranges observed for the collected samples were found to be within the expected ranges for pure compounds, indicating successful separation and purification.

Discussion

The results of this experiment demonstrate the effectiveness of the Acid-Base extraction technique in separating and purifying the components of a mixture. The yields of Benzoic Acid, p-Nitroaniline, and Azobenzene were 76.54%, 87.69%, and 82.39%, respectively, indicating a successful extraction process.

The observed melting point ranges for the collected samples were consistent with the expected values for pure compounds, further confirming the purity of the separated substances. This suggests that the Acid-Base extraction method used in this experiment was efficient in removing impurities and isolating the desired compounds.

It is important to note that the success of the extraction process depends on several factors, including the choice of solvent, the pH of the extracting solutions, and the careful separation of immiscible layers. In this experiment, Dichloromethane was used as the solvent, and Sodium Hydroxide and Hydrochloric Acid were employed as the extracting solutions. The choice of these reagents was based on the known properties of the compounds being extracted.

The separation of the basic and acidic components was achieved by adjusting the pH of the aqueous layers. The formation of conjugate bases and their subsequent regeneration allowed for the isolation of Benzoic Acid and p-Nitroaniline, respectively. Vacuum filtration was then employed to collect the solid compounds.

The final step of the experiment involved the separation of Azobenzene from water through simple distillation. This process allowed for the recovery of Azobenzene in a relatively pure form, as indicated by its melting point range.

In conclusion, the Acid-Base extraction technique successfully separated and purified the components of the mixture, resulting in high yields of Benzoic Acid, p-Nitroaniline, and Azobenzene. The observed melting point ranges confirmed the purity of the collected samples. This experiment highlights the importance of extraction techniques in chemical separation and purification processes.

Conclusion

The Acid-Base extraction experiment was carried out successfully, resulting in the separation and purification of Benzoic Acid, p-Nitroaniline, and Azobenzene from the initial mixture. High yields were obtained for each compound, and their melting point ranges confirmed their purity.