5. [16 pts] Compound Y is in 90 mL of water. The distribution coefficient for co

Question

5. [16 pts] Compound Y is in 90 mL of water. The distribution coefficient for compound Y are as follows K eyelopentane/water 6.2 K dichloromethane-water -2.1 K diethylether!water = 8.0 A) [2pts] The bestsolvent for extraction of Y is: Name Structure 6pts] If 50 mg Y is in 80 mL of water, use the distribution coefficient (K) values for the best solvent, B) [ show how much of Y is extracted into 100 mL of organie solvent. (show your work) C) [6pts] For above question, if a student used 50 mL of organic solvent each time, and he did extrac (he also used 100 mL total of organic solvent) for extracting 50 mg of Y in 80 mL of water. Hown is extracted into 100 mL combined organic solvent? Structure D) 12pts] The worst solvent for extraction of Y is: Name

Explanation / Answer

(A)

Distribution coefficient, K, = Solvent / Extracting solvent

Since,

Kdiethyl ether / water = 8 > 6.2 > 2.1.

So,

The best solvent for extraction of Y is dieyjyl ether. C2H5OC2H5.

(B)

Distribution coefficient, K, = Solvent / Extracting solvent

Kdiethyl ether / water = 8

KD water / diethyl ether = 1/8

We know that

w = W { KD V / (KD V + v) }

Where,
w = solute (Y) remain unextracted
W = Mass of the solute = 50 mg
KD = Distribution coefficient = 1/8
V = volume of the solution containing Y = 80 mL
v = volume of the extracting solvent (Diethyl ether) = 100 mL

Substituting the values, we get;

w = 50 [ { (1/8) x 80 ) } ] / [ { (1/8) x 80 ) } + 100 ]
    = 50 [ 10 / ( 10 + 100) ]
    = 50 ( 10/110)
    = 4.55 mg

So, amount of Y extracted = 50 mg – 4.55 mg = 45.45 mg

(C)

wn = W { KD V / (KD V + v) }n

Where,
w = solute (Y) remain unextracted
W = Mass of the solute = 50 mg
KD = Distribution coefficient = 1/8
V = volume of the solution containing Y = 80 mL
v = volume of the extracting solvent (Diethyl ether) = 100 mL
n = number of times extracted = 2

Substituting the values, we get;

w = 50 [ { (1/8) x 80 ) } ] / [ { (1/8) x 80 ) } + 100 ]2
    = 50 [ 10 / ( 10 + 100) ]2
    = 50 ( 10/110)2
    = 0.41mg

So, amount of Y extracted = 50 mg – 0.41 mg = 49.59 mg

(D)

Since,

Kdichloromethane / water = 2.1 < 6.2 < 8.

So,

The best solvent for extraction of Y is dichloromethane. CH2Cl2.

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