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Extraction Extraction is a general theory for the recovery of a substance from a mixture by bringing it into contact with a solvent which preferentially dissolves the desired material. In organic chemistry, the reaction product is frequently obtained as a solution in water along with other organic and inorganic byproducts.
Let’s get started • To begin this lesson, click on the web address below and view this first 12 pages. • http://www.slideshare.net/Atharsaeedi/extraction-theory • Return to this powerpoint after viewing the first 12 pages.
Let’s do the math By definition, the distribution coefficient is: concentration in the organic layer concentration in the water layer Let us consider compound A: 10g of compound A will dissolve in 100ml ethyl ether (an organic compound) 2g of compound A will dissolve in 100ml of water Calculate the KD for compound A KD=
Determining the KD concentration in the organic layer = 10g/100ml concentration in the water layer 2g/100ml KD= 5 If you are given a solution of 1g of compound A dissolved in 100ml of water, how much could you extract if you did three extractions using 25ml of ethyl ether with each extraction? KD=
Set up the problem Solve for X by cross multiplying two times. Go to the next page to see the value for X.
X = 0.556g • This means that 0.556g of compound A has now moved to the ethyl ether layer. • How much compound A remains in the water? • 1g – 0.556g = 0.444g of compound A in the water. • Now set up the problem for the next extraction:
2nd Extraction Cross multiply twice and solve for X.
X=0.247g • This means that 0.247 more grams of compound A have moved from the water layer to the ethyl ether. • How much compound A remains in the water? • 0.444g-0.247g = 0.197g of compound A are still in the water. • Set up the problem for the third extraction.
3rd Extraction Solve for X and you should obtain X = 0.109g of compound A. What is the total amount of compound A extracted? 0.556g + 0.247g + 0.109g = 0.912g extracted in the ethyl ether. 1g – 0.912g = 0.88g of compound A remaining in the water.
Try another problem? • 15g of compound J dissolves in 100ml of benzene. • 5g of compound J dissolves in water. • You are given a solution with 2g of compound J dissolved in 100ml of water. If you do two extractions with 50ml of benzene in each extraction, how many grams of compound A can you extract from the water?