Caffeine has a distribuation coefficient of about 8 between Me Cl2 and water. Given 30ml of water containing 10 grams of caffeine.
a. How much caffeine can be extracted with one 30mL portion of MeCl2?
b. How much caffeine can be extracted with three 10mL portions of Me Cl2?
c. Which is more efficient?
Ko/a = amt org layer/amt H2O layer.
K is 8
MeCl2 is 30 mL
H2O is 30 mL
Caffeine is 10g
Let X = amount extracted with org layer, then 10-x = amount left in H2O layer.
8 = (x/30)/(10-x)/30
You can cancel the 30 in the denominator. Solve for x.
You can do it three times for three extractions or you can use the following:
fn = [1+Kd*(Vo/Va)]-n
fn = fraction solute REMAINING in H2O layer
Kd is 8 in this case
Vo = volume organic
Va = volume H2O
n = number of extractions
To answer these questions, we need to understand the concept of the distribution coefficient and use it to calculate the amount of caffeine that can be extracted with different portions of MeCl2.
a. To determine how much caffeine can be extracted with one 30mL portion of MeCl2, we need to multiply the concentration of caffeine in water by the distribution coefficient.
1. Calculate the concentration of caffeine in water:
Given that 30mL of water contains 10 grams of caffeine and assuming the density of water is approximately 1g/mL, the concentration of caffeine in water is:
Concentration in water = Amount of caffeine / Volume of water = 10g / 30mL = 0.33 g/mL.
2. Calculate the amount of caffeine that can be extracted with one 30mL portion of MeCl2:
Amount of caffeine extracted = Concentration in water * Distribution coefficient
Amount of caffeine extracted = 0.33 g/mL * 8 = 2.64 grams of caffeine.
b. To find out how much caffeine can be extracted with three 10mL portions of MeCl2, we follow the same steps as in part (a), but adjusting the volume of water:
1. Calculate the concentration of caffeine in water:
Given that the total volume of water is now 3 x 10mL = 30mL, the concentration of caffeine in water remains the same:
Concentration in water = 0.33 g/mL.
2. Calculate the amount of caffeine that can be extracted with each 10mL portion of MeCl2:
Amount of caffeine extracted with each 10mL portion = Concentration in water * Distribution coefficient = 0.33 g/mL * 8 = 2.64 grams.
To find the total amount of caffeine extracted, we multiply the amount extracted with one portion by the number of portions:
Total amount of caffeine extracted = Amount of caffeine extracted with each portion * Number of portions
Total amount of caffeine extracted = 2.64 grams * 3 = 7.92 grams of caffeine.
c. To determine which extraction method is more efficient, we compare the total amount of caffeine extracted with each method:
For one 30mL portion of MeCl2, the amount of caffeine extracted is 2.64 grams.
For three 10mL portions of MeCl2, the amount of caffeine extracted is 7.92 grams.
Therefore, the extraction with three 10mL portions is more efficient as it extracts a higher total amount of caffeine.