• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Objective: To isolate benzoic acid from the toluene-benzoic acid mixture by liquid-liquid extraction and purify the benzoic acid by recrystallization.

Extracts from this document...

Introduction

´╗┐Experiment 1: Separation of organic compounds Experiment 2: Recrystallization and Determine melting point of organic compounds Objective: To isolate benzoic acid from the toluene-benzoic acid mixture by liquid-liquid extraction and purify the benzoic acid by recrystallization. Introduction Extraction is a powerful separation technique. Normally, it is useful when the compound of interest tend to be distributed itself in to one phase. In the separatory funnel, 2 phases are present , aqueous and organic phase. The distribution of each phases of a certain compound depends on its solubility and the solubility ratio is called the distribution coefficient, KD. Some approach can change the physical and chemical factors in order to obtain different distribution coefficient of a certain compound. For example, adding a large amount of sodium chloride to the aqueous solvent to produce a saturated solution. Crystallization is a method to purify solid organic compounds. First of all, selection of a suitable solvent for dissolving the solute of interest is required. Usually, the solute should be insoluble in the solvent at room temperature but we be soluble in the solvent at a higher temperature. Therefore, water is used in the experiment to dissolve benzoic acid. During the cool down process, the compound will crystallize but other impurities will be rejected from the crystal lattice and thus pure compound can be obtained. Melting points determination is able to find out the physical properties of a compound and also the purity. ...read more.

Middle

The conical flask was cooled down to room temperature and was then placed in an ice-bath. The recrystallized solid was filtered by suction filtration. The filter paper was placed on the Büchner funnel and was wet by de-ionized water. The conical flask was rinsed with small portion of de-ionized water. The crystals was dried for 10 minutes by the suction drawing air through the funnel and was then transferred onto a filter paper. Another filter paper was placed on the solid and two pieces of filter paper was pressed slightly for further drying. The crystals were weighed and was transferred into a clean and dry plastic b Result and Calculation: Experiment 1 (Extraction) Amount of toluene-benzoic acid mixture 30.0 mL Weight of product (1st conical flask) 2.354 g Weight of product (2nd conical flask) 0 g % Yield of theorem 60 g/L x 0.03 = 1.8 g % Yield of the extraction (2.354 g / 1.8 g) x 100% = 130.8% Table 1. The informations and data in experiment 1. Experiment 2 (Recrystallization) Amount of Raw Product used (Expt. 1) 2.21 g Weight of crystals (Expt. 2) 1.374 g % Yield of recrystallization 1.374 g / 2.21 g x 100% = 62.17% Color & Form of crystals Transparent & needle shape Efficiency of extraction and recrystallization of benzoic acid in toluene-benzoic acid mixture 1.374 g / 1.8 g x 100% = 76.3% Table 2. The informations and data in experiment 2. Melting Point Range (°C) Raw Product (Expt. ...read more.

Conclusion

Sodium benzoate was then converted to the benzoic acid by the reaction with 10% hydrochloric acid solution. There is no any observable benzoic acid in second conical flask which means the majority of benzoic acid was extracted in first conical flask. After extraction, the percentage yield of benzoic acid was 130.8%. The main reason may be water was not completely removed or other impurities were present. This reason can be further proved by the melting point of raw product. The melting point of raw product was 120-121 °C, which is lower than the benzoic acid standard. After crystallization, the percentage yield of crystals was 62.17%. Part of the benzoic acid may be lost during placing the conical on the steam bath because the temperature was too high and thus the benzoic acid was evaporated out. A narrow range of melting point of mixed product was obtained, which confirms the crystals are benzoic acid and relatively high purity of benzoic acid was obtained because of the same melting temperature to the standard. In order to obtain higher percentage yield of crystal products, at least 63.5mL of 10% aqueous hydrochloric is used instead of 35 mL. The temperature of steaming process should be lower to avoid evaporation of benzoic acid. Also, care should be taken to collect all the benzoic acid on the surface of Büchner funnel or on the filter paper. Conclusion: To conclude, the percentage yield of benzoic acid from the toluene-benzoic mixture was 76.3% and the melting point was 117.9-121°C. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our University Degree Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related University Degree Chemistry essays

  1. Stereochemistry of Butenedioic acid. Objective: To study ...

    Maleic and fumaric acid are two of the examples shown below. Maleic acid (cis-butendioic acid) Fumaric Acid (trans-butendioic acid) Generally, they have similar but not identical chemical properties and very different physical properties, e.g. melting point, solubility, density and stability.

  2. Bromination of acetanilide by using melting point

    However, many aromatic compounds are readily brominated when treated with bromine in the presence of catalyst of a Lewis acid which is Iron (III) bromide as the mechanism is shown in the introduction. This experiment is runned in mild conditions which glacial acetic is used.

  1. A 0.60 um film of silicon dioxide is to be etched with a buffered ...

    complete the etching process is exactly the time required for the etchant to etch to the oxide-substrate interface. Therefore, in a perfect etch, the etching process would have ended at the exact moment the etchant touched the oxide-substrate interface. If the etching process had ended at the exact moment the

  2. Objective: 1) To perform an acid-alkaline extraction. 2) To recover benzoic acid and ...

    The formula for calculating the percentages of recovery: The formula for calculating the relative accuracy of melting point: Chemicals/reagents: Benzoic acid (1g), p-dichlorobenzene (1g), ether (40ml), 10% (30ml), conc. , distill water, (35ml), anhydrous . Glass wares: Separatory funnel, Buchner funnel.

  1. Forensic Chemistry - Ion Selective Electrode. The objective of experiment is to determine ...

    This is why dilute samples are preferred for measurement with ISE's. It is possible to 'fix' the solution so that activity and concentration are equal. This can be done by adding a constant concentration of an inert electrolyte to the solutions under test.

  2. Determination of the density of an unknown liquid

    The filled pycnometer was left at room temperature°C for 5 minutes. 4. The neck of pycnometer was picked up by using two layers of papers between the fingers to avoid expansion of the pycnometer due to heat of the hand.

  1. The two central objectives of this experiment are the production of Aspirin from esterification ...

    The initial amount of salicylic acid was dissolved in the solution of acetic anhydride and concentrated sulphuric acid, it has not completely dissolved into the solution, even when it was heated. This could have a slight impact on the results of the overall yield of aspirin because it was possible that not all of the salicylic acid was synthesized.

  2. The objective of this experiment is to determine how a buffer system resists large ...

    The pH of solution of buffer containing acetic acid and sodium acetate is calculated as by first identifying the acid-base properties of the various species in solution, and then consider the possible proton transfer reaction these species can undergo. Since acetic acid is largely undissociated in aqueous solution and since

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work