3. Chloroform is an excellent solvent for extracting caffeine from water. KD 9 f

Question

3. Chloroform is an excellent solvent for extracting caffeine from water. KD 9 for caffeine in chloroform-water at 25 C. What weight of caffeine would be recovered from a solution of 4.0g caffeine in 100 mL water by a single extraction of 100 mL of chloroform? extractions using 50 mL of chloroform each time? layer: What could you do to determine which layer is which? 4. For the situation in Question 3, what total weight of caffeine could be removed by two 5. Suppose that, during an extraction, you lost track of which flask contained the aqueous

Explanation / Answer

3. Given that ,

KD = 9

i.e. when volume of both the solvent is same (say 100 mL, both) then 90% of caffeine comes in chloroform.

Hence, if 4.0 g of caffeine in 100mL water is extracted with 100 mL chloroform,

(4.0 X 90) / 100 = 3.6 g

i.e. 3.6 g of caffeine could be extracted once.

4. Given that ,

KD = 9

i.e. solvent ratio 1:1 = extraction ratio 9:1            i.e. (9/10)x100 = 90%

hence , solvent ratio 1:2 = extraction ratio 9:2     i.e. (9/11)x100 = 81.81%

Hence, first time 81.81% of 4.0 g caffeine = 3.2727 g caffeine will be extracted.

Then second time 81.81% of 4.0-3.2727 = 0.727273 g caffeine = 0.5950 g caffeine will be extracted.

Hence, total caffeine extracted = 3.2727 g + 0.5950 g

= 3.8677 g

5. If I lost the track of which flask contain aqueous layer, there will be 2 flasks with me.

I will add small amount of chloroform to both flask and look for miscibility.

The flask were my added chloroform does miscible with the existing solution, that flask is of aqueous layer.

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

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