Objectives: 1. To study the crystallization process. 2. To identify the best suitable solvent to use for the crystallization process. 3. Gain an experience in purifying an organic compound by the techniques of the crystallization.
Introduction. Crystallization is a technique which chemists use to purify solid compounds. It is one of the fundamental procedures each chemist must master to become proficient in the laboratory.
Organic compounds isolated from their natural sources or prepared synthetically in the laboratory are usually impure. The impurities might be compounds with properties similar to those of the desired compounds, reaction-starting materials, products of side reactions, or simple dust or soil. Pure substances are not only important to chemists in their studies of matter but also are vital in other areas of study such as medicine where those substances might be used as medications Crystallization is based on the principles of solubility: compounds (solutes) tend to be more soluble in hot liquids (solvents) than they are in cold liquids. If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound. Impurities are excluded from the growing crystals and the pure solid crystals can be separated from the dissolved impurities by filtration.
Chemical requirement.
Solvent: Distilled water, Ethanol, and Acetone.
Solute: Acetanilide.
Result: Data and Report Sheet. 1.1 Choosing a suitable solvent. Solvents | solubility | Appearances and quantity of the crystal at room temperature | | Room temperature | Hot temperature | | Distilled water | insoluble | soluble | Crystal like white needle | Ethanol | good | - | No crystal | Acetone | good | - | No crystal |
Why do you choose this solvent?
It is because Acetanilide is more soluble in hot water but not in old water, also sugar is impurity it is very soluble in cold water therefore, it fits the essential characteristics needed for the suitable solvent. 1.2 Crystallization
Appearance of acetanilide sample (before crystallization): white dust.
Mass of acetanilide sample (before crystallization): 2.15g.
Appearance of acetanilide crystal: jelly white like white needle.
Mass of filter paper: 1.42g
Mass of filter paper +acetanilide crystal:
Mass of acetanilide crystal:
Calculation.
% yield of crystal =
You May Also Find These Documents Helpful
-
The purpose of this lab is to purify solids contaminated by relatively small amount of impurities by a technique called Recrystallization. Compounds that have different solubility at different temperature usually can be recrystallized.…
- 503 Words
- 3 Pages
Satisfactory Essays -
even after scratching with a glass rod. Explain why this crystallization failed. What would you have to do at this point to make the crystallization work…
- 358 Words
- 2 Pages
Satisfactory Essays -
To make crystals, you need to make a very special kind of solution called a supersaturated solid solution. Here’s what that means: if you add salt by the spoonful to a cup of water, you’ll reach a point where the salt doesn’t disappear (dissolve) anymore and forms a lump at the bottom of the glass.…
- 976 Words
- 4 Pages
Good Essays -
The second figure illustrates the process used in the laboratory to form bromoacetanilide. Recrystallization is of key importance in the experiment because this method is used to obtain the crystals. Recrystallization is a purification technique that removes impurities from a sample. An impure solid is placed in a liquid for example water or ethanol. It is then heated making the solid dissolve into the solvent. When the solvent cools back down again, the solid will precipitate out of the solution and leave the impurities behind, still dissolved in the solvent. This method purifies the solid.…
- 1035 Words
- 5 Pages
Better Essays -
Recrystallization, referred to as the second crystallization, is a method in which two crystallization processes are performed. It is a process of dissolving the solid to be crystallized in a hot solvent or solvent mixture and then cooling the solution slowly. This technique can be used for large or small quantities of materials, and is usually very effective and efficient. The most important aspect of the recrystallization technique is the selection of the solvent. A large number of solvents are commonly used for recrystallization of organic compounds. Among these are water, ethanol, ethyl ether, methanol, and hexane to name just a few. A solvent, which works beautifully for one recrystallization, may be totally unsuitable for purification of a different compound - the choice for recrystallization solvent is made on a case-by-case basis. This is because of the variation of solubility of different organic compounds in these solvents. A desirable recrystallizing solvent would increase the solubility of the solute as the temperature rises.…
- 1376 Words
- 6 Pages
Better Essays -
The product was placed in a beaker, and enough aqueous methylated spirit (IMS) was added whilst the mixture was heated to dissolve the product. The mixture was then left to cool and was placed in ice to aid crystallization. The product was vacuum filtrated after a few minutes of standing in ice and the crystals were collected and dried in a vacuum oven at 40 degrees celsius. The mass of the crystals was calculated and the melting point was determined.…
- 652 Words
- 3 Pages
Good Essays -
We were required to complete parts B, C, D and E. The procedure for parts B, C and D were followed by the book. (CHMY 221/223 “A Microscale Approach to Organic Laboratory Techniques,” 5th Edition, Donald L Pavia, George S. Kriz, Gary M. Lampman, Randall G. Engel, 2013, Cegage Learning pages 26-30 and 687-693). Part D involved identifying an unknown. Part E involved using polarity and solubility theories to determine the best solvent for crystallization, which compound was too soluble and which compound was not soluble enough. The Merck Index was used to get exact solubility’s and polarities to determine which solvent would be best to crystallize the given solute.…
- 1182 Words
- 5 Pages
Powerful Essays -
3. Outline the successive steps in the crystallization of an organic solid from a solvent and state the purpose of each operation.…
- 587 Words
- 2 Pages
Good Essays -
Crystallization is a liquid and solid chemical separation that takes place due to mass transfer of a solute from the liquid solution to a pure solid crystalline, a phase that occurs after the reaction occurs.…
- 741 Words
- 3 Pages
Good Essays -
Nucleation As in solidification, nucleation occurs most easily on surfaces already present in the structure, thereby minimizing the surface energy term. Thus, the precipitates heterogeneously nucleate most easily at grain boundaries and other defects.…
- 457 Words
- 2 Pages
Good Essays -
The objective of this lab is to introduce the participating students to qualitative analytical chemistry. The group will be given an unknown pure organic liquid sample and will need to perform a series of tests in order to identify the species in question. The tests being: determining the boiling point using two methods (distillation and capillary tube), determining the refractive index, and obtaining UV/VIS and FT-IR absorption spectra. After the results from the various tests are obtained, the boiling point and refractive index should be compared to literature data while the absorption spectra should be analyzed. Finally, this should allow the group to accurately identify the nature of the chemical species that constituted the sample.…
- 559 Words
- 3 Pages
Good Essays -
Crystallization is when magma cools off; crystallization is also the formation of an igneous rock. This occurs in multiple ways, one is being under the earth’s surface or after an eruption on the surface. A number of weathering elements are exposed to this newly formed rock. The rock will be deteriorated by these weathering elements, turning them into sediments. This is where the water cycle comes into to play, it often carries sediment down the watershed into any number of basins: deserts, swamps, the ocean, or riverbeds.…
- 341 Words
- 2 Pages
Good Essays -
Crystallization only happens in a floatng charge. Crystallization is the conversion from a floatng chrge to a fxed chrge. The event of crystallization occurs only when the compny go into liquidaton or stops to cary on its busness, the court or debenture holders apoint a recever and when a specfic evnt has occurred for automatc crystalization.…
- 785 Words
- 4 Pages
Good Essays -
The fundamental information that environmental engineers and scientists need concerning organic chemistry differs considerably from that which the organic chemist requires. This difference is due to the fact that chemists are concerned principally with the synthesis of compounds, whereas environmental engineers and scientists are concerned, in the main, with how the organic compounds in liquid, solid, and gaseous wastes can be destroyed and how they react in the environment. Another major difference lies in the fact that the organic chemist is usually concerned with the product of the reaction: the by-products of a reaction are of little interest to him or her. Since few organic reactions give better than 85 percent yields, the amount of by-products and unreacted raw materials that represent processing wastes is of considerable magnitude. In addition, many raw materials contain impurities that do not enter the desired reaction and, of course, add to the organic load in waste streams. A classical example is formaldehyde, which normally contains about 5 percent of methanol unless special precautions are taken in its manufacture. Unfortunately, organic chemists have presented very little information on the nature of the by-products of reactions to aid environmental engineers and scientists in solving industrial and hazardous waste problems. Fortunately, this is changing because of the large liabilities that companies now face from discharge of environmental pollutants. Awards are now being given for “green chemistry,” that is, for changing the ways chemicals are produced in order to reduce the environmental harm they or their production cause. The environmental engineer and scientist, like the biochemist, must have a fundamental knowledge of organic chemistry. It is not important for either to know a multiplicity of ways of preparing a given organic compound and the yields to be expected…
- 35092 Words
- 141 Pages
Powerful Essays -
Organic chemistry is one of the ‘branches’ of chemistry and is seen as distinct from other branches, such as inorganic and physical chemistry.…
- 717 Words
- 3 Pages
Good Essays