Using english to Predict rendement of product a reaction

PURIFICATION REKRISTALIZATION

CHAPTER I

PRELIMINARY

A. Background

            Getting a chemical with a very high purity is essential for chemical purposes. The method of purifying a common solid is recrystallization (the formation of recurrent crystals). This method essentially considers the difference in the solubility of the solids to be purified by impurities in a particular solvent or when possible in other solvents which solubilize only the impurities. Such purification is mostly done in industries (chemicals) or laboratories to improve the quality of the substance concerned.

            In the use of recrystallization techniques are usually backed up because of solid organic compounds isolated from rare pure organic reactions. The compound is usually contaminated with a few other compounds (impuritis) produced during the reaction. Purification of solids by crystallization is based on differences in solubility in certain solvents or solvent mixtures. When a crystal is very soluble in one solvent and very insoluble with another solvent it will give a satisfactory recrystallization result.

                   Technique separation or purification of a substance that has been contaminated or mixed can be done in several ways, including: filtering, recrystallization, decantance, absorption, sublimation, and extraction. Filtering is a separation process that is based on differences in particle size. For example filtering of lime suspension in water. Recrystallization is the whole process of dissolving the solute and crystallizing it again. An example is the purification of the salt of the kitchen. Decantation is the process of separating a substance from its mixture by depositing another substance, based on a larger mass of the type being in the lower layer. For example a mixture of sand and water. Absorption is the process of separating a substance using absorption techniques. For example, syrup is filtered by norit. Sublimation is the process of separating and purifying a sublimal substance of a mixed particle or substance. An example is the separation of naphthalene from the mixture with salt. Extraction is the process of purifying a mixed substance using the polarity properties of a substance using a separating funnel. An example is the separation of cooking oil from the mixture. However, in this practice it purifies solids by recrystallization method.

            Benzoic acid, C7H6O2 (or C6H5COOH), is a white crystalline solid and is the simplest aromatic carboxylic acid. The name of this acid comes from gum benzoin (sap of incense), which was once the only source of benzoic acid. This weak acid and its derivative salts are used as food preservatives. Benzoic acid is an important precursor in the synthesis of many other chemicals. For all synthesis methods, benzoic acid can be purified by recrystallization from water, because benzoic acid dissolves well in hot water but is bad in cold water. Avoiding the use of organic solvents for recrystallization makes this experiment safe. Other possible solvents include acetic acid, benzene, petroleum ether, and a mixture of ethanol and water.

            Based on the above statements it is necessary to know the way purification of solids by recrystallization, using a compound as a sample, so as to distinguish the separation process through recrystallization method with other methods. Therefore, this recrystallization purification experiment is performed.

B. Purpose of Practicum

            The purpose of this experiment is to purify solids by recrystallization.

C. Trial Principle

            The experimental principle of this practicum is to purify the contaminated benzoic acid with the principle of recrystallization based on its solubility in a particular solvent (water).

CHAPTER II

THEORY OF SUPPORT

            Recrystallization is a purification technique of a solid of the mixture or impurity effected by recrystallizing the agent after it is dissolved in a suitable or suitable solvent. There are several conditions for a solvent to be used in the crystallisation process, which is to provide a considerable difference in solubility between the purified substance and the impurities, leaving no impurities in the crystal, and easily separated from the crystals. In the case of purification of NaCl salt by solvent recrystallization technique used is water. The basic principle of recrystallization is the difference in solubility between the substances to be purified by the solubility of the mixer or the contaminant. The formed solution is separated from each other, then the desired solution of the substance is crystallized by saturating it (reaching the supersaturation or saturated condensation). Torites have 4 methods to create supersaturation by changing temperature, evaporating olvens, chemical reactions, and changing the solvent composition (Agustina, 2013).

            The impurities present in the crystals consist of two categories, ie impurities present on the surface of the crystal and impurities present in the crystal. The impurities present on the surface of the crystal originate from the mother liquor carrying on the crystal surface at the time of separation of solids from the parent solution (retentionliquid). The impurities on the crystalline surface can be separated only by washing. The liquid used for washing should have the property to dissolve the impurities but not dissolve the crystalline solids. One of the liquids that satisfies the above properties is the saturated solution of the crystal material to be washed, but can also be used in general solvents that meet the krteria. The impurities inside the crystal can not be removed by washing. One way to remove impurities present in crystals is by recrystallizing, by dissolving the crystals and then crystallizing them again. One of the advantages of the crystallization process compared to other separation processes is that impurities can only be carried in crystals if they are well oriented in the crystal lattice (Puguh, 2003).

            The impurity binder is a substance or substance which can be used to bind foreign substances that are unwanted in pure substances. In theory salt circulating in the community as consumption salt should have a minimum NaCl content of 94.7% for non-iodized salts. According to SNI number 01-3556-2000, iodized salt is consumption salt containing main component of NaCl (Sodium Chloride / mineral) 94,7%, water maximum 7% and Potassium Iodate (KIO3) mineral 30 ppm, and other compounds according With the requirements specified, but in fact the NaCl content of the kitchen salt is substantially below the standard.Therefore, this study was conducted to determine the elevated levels of purified NaCl without the addition of impurities binder, with the addition of Na2C2O4 and Na2CO3 impurities binder or the addition of Na2C2O4 and NaHCO3 with Varying concentrations in the manufacture of salt from old water (Sulistyaningsih, 2010)

            The high value of anthocyanin rendement obtained from the extraction using methanol and 1% HCl and 95% citrine added 3% citric acid compared to using other solvents due to the matching of polarity between the solvent and the dissolved material, so that the solvent mixture is able to dissolve more anthocyanins out of the protoplasm Red cabbage cells and yield more rendemen. This opinion is supported by Pifferi and Voccari (1983 in Sari 2003) explaining that the amount of rendement is affected by the effectiveness of the solvent to extract the anthocyanin, which will ultimately affect the stability of the anthocyanin during the extraction process (Wirda, 2011).

            The yellow solids present in the fractions A and D are recrystallized using the same solvent ie n-hexane acetone. The choice of the solvent is based on the principle of recrystallization ie the sample which is not soluble in a solvent at room temperature but soluble in solvent at room temperature. Thus recrystallization involves the initial step of dissolving the compound to be purified in the least possible solvent or solvent mixture in the heat state or even to the boiling temperature so as to obtain a clear solution and the subsequent step of cooling the solution which will lead to crystalline formation and then separated by filtration (Paint, 2010).

CHAPTER III

PRACTICAL METHOD

A. Tools and Materials

1. Tools

A. Glass cup 100 mL 1 piece

B. Buchner funny 1 piece

C. Spatula 1 piece

D. Vacuum pump 1 piece

E. Stir bar 1 stem

F. Bottle spray 1 piece

2. Materials

A. Benzoic acid is contaminated

B. Distilled water

C. Ice water

D. 2-sheet filter paper

B. Work Procedures

1. Heat the distilled water to boiling

2. Considering Acid Benzoate contaminated as much as 1 gram

3. Incorporate the contaminated benzoic acid into a beaker

4. Dissolving Acid Benzoate is contaminated with hot water

5. Screen the benzoic acid solution in a hot state with a Buchner funnel

6. Separate the residual (impurities) with the filtrate

7. Cool the filtrate with ice cubes to form a crystal

8. Menyaringkristal formed

9. Separating the Crystalline Benzoic Acid with the solvent (water)

10. Acquired 0,543 gram of Benzoic Acid Crystals

11. Determining the weight of rendemen (%)

CHAPTER IV

RESULTS AND DISCUSSION

A. Data on Practicum Results

  

No	Treatment	Observations
1	Distilled water is heated to boiling	Boiling water
2	1 gram tamarind benzoic acid dissolved with hot water	The solution is clear and white deposits
3	The solution is filtrate using a Buchner funnel	Obtained filtrate and filtered
4	The filtrate is cooled and filtered	Crystal form
	The crystal of benzoic acid is separated from the solvent	Acid Crystal benzoate is obtained from the impurities
5	The crystal is weighed	As many as benzoic acid crystals
6	Determined weight the rendement	the yield of rendement results of 54.3%

B. Calculations

The weight of empty filter paper = 0.76 grams

Weight of sample (benzoate acid contaminated) = 1 gram

Crystal Weight in filter paper = 1.303 grams

The weight of crystal benzoic acid = 1.303 grams - 0.76 grams

                                                             = 0.543 grams

Dit: Rendemen Level ...?

Resolution:

Rendement = 54.3%

Impurities = 100% - 54.3%

                 = 45.7%

C. Discussion

            Separation and purification is the process of separating two or more substances which are mutually mixed and to obtain a pure substance from a substance that has been contaminated or mixed. Recrystallization is one of the means of purifying a commonly used solid, in which the said substances or solids are Dissolved in a solvent and then recrystallized. This depends on the solubility of the substance in a particular solvent when the temperature is magnified. Since the total concentration of impurities is usually smaller than the concentration of the purified substance, when cold, the low concentration of the impurities but in the temporary solution of the highly concentrated product will precipitate.

            The steps in recrystallization are (1) Dissolution (2) Filtering (3) Heating (4) Cooling. Some good solvent requirements for recrystallization include: a) having high solvency at high temperatures and low solvency; B) Produce fine crystals of the purified compound; C) may dissolve other compounds; D) Has a relatively low boiling point (easily separated by pure crystals); E) The solvent does not react with the purified compound.

            A precipitate is easily filtered and washed largely depending on the structure of the precipitate morphology, which comprises the shape and size of the crystals. The larger crystals formed during the course of precipitation, the easier the filtration process may be and (although not necessarily) the faster the crystals -the crystal will drop out of the solution, which will help filtering. The shape of crystals is also important. Simple structures such as cubes, octahedrons, or needles, are very advantageous, because they are easy to wash after filtering. Crystals with more complex structures, which contain curves and holes, will retain mother fluid, even after careful washing. With a precipitate comprising such crystals, quantitative separation is less likely to be achieved.

            The size of the crystals formed during the precipitation, depends on two important factors: the rate of nucleation (nucleation) and the rate of crystal growth. If the rate of formation of a nucleus is high, a lot of crystals will form, but none of these will grow too large, so a precipitate of small particles is formed. The rate of nucleation formation depends on the degree of saturation of the solution. The higher the degree of saturation, the more likely it is to form a new nucleus, so the greater the rate of core formation. The rate of crystal growth is another factor that affects the size of the crystals that formed during the deposition. If this rate is high, large crystals will form that are affected by degrees of saturation.

            Benzoic acid used in this experiment is benzoic acid that is not pure or still dirty. Therefore purification of the benzoic acid to be free of impurities by heating with the solvent. The solvent used is water. Water is used as a benzoic acid solvent because the boiling point of water is lower than the benzic acid melting point of 249 ˚C. According to the requirements as an appropriate solvent, the solvent's boiling point must be low to facilitate the crystal drying process formed.

            Under this condition, the boiling point of water as the solvent is lower than the boiling point of the benzoic acid so that the desired crystal at the time of drying may be formed, the use of water as a benzoic acid solvent is also related to the solubility. In accordance with the condition of the second solvent is solvent can only dissolve the substance to be purified and not dissolve the pollutant. The reaction between water and benzoic acid causes the formation of hydrogen bonds, this is what causes water to dissolve benzoic acid.

            The first step is to dissolve the benzoic acid in solid form to become a solution. The solvent used to dissolve this benzoic acid is a suitable solvent. It is intended that the diluted benzoic acid may dissolve completely. Benzoic acid dissolved in hot water will decompose into ions The next step is done after heating is filtering the solution into a container by using filter paper. This filtration is intended to separate between the soluble substance and the impurities in order to obtain a more pure substance, but to obtain maximum results then this treatment is done by using a tool known as buchner funnel.

            The next step again is to cool down. If crystal has not formed then the solution is saturated by evaporation, so that the sediment can be formed easily. But if the crystals have begun to form, then filtering is done by using filter paper. It aims to separate the sediment from the solution. The filtrate of the filtrate will be used for crystallization at a later stage. In order for this recrystallization process to run properly, the impurities have greater solubility than the desired compound. If this is not fulfilled then the dirt will co-crystallize with the desired compound. The impact causes the crystals obtained is not pure anymore, where the purity of a substance is determined by the yield obtained, the higher the yield of a substance the higher the purity will be higher while the smaller the yield value obtained from a substance the lower the purity level and from the results of this experiment Obtained a pure benzoate acid weight of 0.543 grams. Thus, the yield of the benzoic acid crystals obtained from the ratio of pure benzoic acid to benzoic acid was contaminated by 54.3%. So that the pollutants (residues) in the sample of benzoic acid were contaminated in this experiment of 45.7%. Sedikinya results obtained rendemen, can be caused by dissolving benzoic acid and followed by filtering the water temperature is not too hot so that benzoic acid is not very soluble (soluble perfectly).

CHAPTER V

CLOSING

A. Conclusion

            Based on the experimental results and observations made it can be concluded that purification is recrystallized based on the difference in solubility between the purified substance and the impurities in a particular solvent. Crystalline Acid Benzoic acid can be separated and recovered from its impurities (contaminated benzoic acid). Crystalline Acid Benzoic which can be recovered as much as 0.543 grams with the amount of rendemen as much as 54.3%.

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