Can you help me answer these question based on my data? Thanks Name Recrystalliz
ID: 531307 • Letter: C
Question
Can you help me answer these question based on my data? Thanks
Name Recrystallization OBJECTIVES Purify an impure of an antibiotic Practice the crystallization technique. INTRODUCTION The purpose of this experiment is to introduce the technique of crystallization. a very common procedure used to purify crude solids in the organic laboratory. The general technique involves dissolving the material to be crystallized in a hot solvent and cooling the solution slowly. The dissolved material has a decreased solubility at lower temperatures and will separate from the solution as it is cooled. This phenomenon is called if the growth is slow and selective or precipitation if the process is rapid and nonselective. Since the impurities are usually present in much smaller amounts than the compound being crystallized, most of the impurities will remain dissolved in the solvent even when it is cooled. The purified substance can then be separated from the solvent and impurities by filtration. in this experiment, you carry out a crystallization of impure sulfanilamide using 95% ethyl alcohol as the solvent. will of the sulfa drugs, the first generation of antibiotics to be used in successfully Sulfanilamide is one treating many major diseases such as malaria, tuberculosis, and leprosy. Sulfanilamide The solubility of sulfanilamide in 95% ethyl alcohol is given in the following table: Temperature Solubility (mg/mL) 200C 24 40°C 60°C 88 Notice 210 that the solubility increases significantly as the temperature increases. Therefore, 95% ethyl alcohol is an excellent solvent for crystallizing A graph of this is shown on the next page You will crystalize a sample of impure sulfanilamide by dissolving it in the minimum amount of boiling 95% ethyl alcohol (78 oC) and then cooling the solution, first to room temperature, and then to 0 C in an ice-water bath crystals The purity of the final material after will be determined by observing the color of youn and by performing a melting point on your sample. You will also weigh your sample and calculate the percent recovery. It is not likely that you will obtain a 100% recovery. This is true for several reasons experimental loss, the original sample is not 100% sulfanilamide, and some sulfanilamide is soluble in the solven even at 0 C. Because of this latter factor, some sulfanilamide will remain dissolved in the mother liquor (the liquid remaining after crystallization has taken place)Explanation / Answer
Answer to Q1)
Pure sulfanilamide crystals are white coloured as it does not have the necessary chromophore to absorb visible radiations. The yellow colour is from the presence of some coloured impurities.
Answer to Q2)
The reasons for recovery not being 100% are as follows:
a)The sample provided was impure and not 100% sulfanilmide. Hence, the recovery can never be 100%. Had the recovery been 100%, it suggests that the impurity was not separated from the product and the experiment was unsuccessful.
b)The solubility of the product is not completely insoluble at 0 deg C. 14 mg mL-1 of sulfanilamide will still be retained in the mother liquor. This contributes to experimental loss.
c)Other factors such as loss of product on the filter bed, rise in temperature while filtration will also contribute to experimental loss.
Answer to Q3)
Recrystallisation is a process of purification of a substance. The process involves making a saturated solution of the substance i.e. dissolving entire stuff in minimum amounts of solvent followed by cooling it to crystallise it again. Thus the solubility of substance at higher temperature determines the quantity of solvent required for making saturated solutions and have efficient recrystallisation.
At 78 deg C the solubility of sulfanilamide is 210 mg mL-1 while at 40 deg C it is only 46 mg mL-1. If the solution containing impure sulfanilamide and ethanol is heated to only 40 deg C, not entire quantity of this impure product will be soluble in ethanol and some impurity will still be insoluble. When this solution is cooled to 0 deg C and filtered, the impurity will be carried with the product and the resultant product will not be completely pure.