You have 1.00 g salicylic acid dissolved in 50.0 mL dichloromethane, and you hav

Question

You have 1.00 g salicylic acid dissolved in 50.0 mL dichloromethane, and you have 90.0 mL of water available in your hood. The partition coefficient, K, for CDCM/C water is equal to 3.5. If you want to maximize the amount of salicylic transferred to the water layer, would you do one extraction with 90.0 mL of water or two extractions with 45.0 mL of water? Calculate the number of grams of salicylic acid transferred in both scenarios to support your answer. (1 pt) What could you do to your water solution to increase the amount of salicylic acid transferred? What will this do to K, above? (You can still only use 90.0 mL total.) (1/2 pt)

Explanation / Answer

(a) Kd = g in DCM/g in water

with 1 g salicylic acid in 50 ml

let x g be the amount of salicylic acid extracted in water with 1 90 mL portion

then 1-x g be the amount left in DCM phase

Kd = 3.5 = (1-x/50)/(x/90)

3.5x/90 = 1-x/50

x = 3.4 g

So, 3.4 g is extracted in water phase

Now lets do double extraction with 45 ml portion of water each time

let x g be the amount of salicylic acid in water extracted frist time, then,

Kd = 3.5 = (1-x/50)/(x/45)

3.5x/45 = 1-x/50

x = 0.206 g

amount remaining in DCM phase = 1-0.206 = 0.794 g

Second extraction, again say x g extracted in water, then,

Kd = 3.5 = (0.794-x/50)/(x/45)

3.5x/45 = 0.794-x/50

x = 0.162 g

So total amount extracted after 2 45 mL portion of water extraction = 0206+0.162 = 0.37 g

This is higher then the amount extracted with 1 90 ml portion of water.

So multiple extraction is a better method for isolating salicylic acid.

(b) If we increase the number of extraction steps say, we do the extraction with 22.5 ml portion of water 4 times, the amount of salicylic acid in water would increase.

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.