Post a New Question

Organic Chem

posted by .

A 20 g mixture containing 95% (by weight) of A and 5% of B is recrystallized in toluene (b.p. 110 C). Solubility for compound A is 1.5 g @20 degrees and 10 g @ 110 degrees. For compound B solubility is 0.5 g @20 degrees and 8 g @ 110 degrees. What amount of solvent is needed to obtain pure A and how much pure A will be recovered?

  • Organic Chem -

    Nowhere in your problem do you say what the volume is for the solubility. In most cases it is quoted as 100 mL; therefore, I ASSUME that 1.5 g @ 20 C MEANS 1.5 grams A will dissolve in 100 mL toluene at 20 C, etc.
    20 g sample is
    95%A or 20 x 0.95 = 19 grams A.
    5% B or 20 x 0.05 = 1 grams B.

    How much toluene do we need to dissolve the 19 g A? It is 100 mL x (19/10) = 190 mL toluene needed to dissolve 19 grams A @ 110 C. Will that dissolve all of the B? Yes, because you have only 1 g B and the solubility of B at 110 C is 8 grams.

    Now we cool the 190 mL toluene to 20 C. How much A comes out?
    1.5 g x (190/100) = 2.85 grams A dissolve; thus, 19-2.85 = ?? grams recrystallize so your percent recovery (although the problem doesn't ask for that) is (16.15/20)*100 = ??
    You may want to check to see if it will be contaminated with B. We had the 1 g B dissolved in 190 mL toluene at 110 C. At 20 C, B dissolves to the extent of
    0.5 x (190/100) = 0.95. Since we had 1.0 g B, all of it will stay in solution at the lower temperature. Check my thinking.

  • Organic Chem -

    Your answer is correct.

  • Organic Chem -


  • Organic Chem -


Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Math

    From a window 40 feet above the ground in a certain building, the angle of elevation to a window in a second building is 43 degrees. If the distance between the buildings is 110 feet how far above ground level is the second window. …
  2. chem

    a compound containing only boron, nitrogen and hydrogen was found to be 40.3% B, 52.2%N, and 7.5% H by mass. If 3.301g of this compound is dissolved in 50.00g of benzene, the solution produced freezes at 1.30 degrees celsius. If Kf(freezing …
  3. organic chemistry

    The solubility of a compound is 59g per 100mL in boiling methanol and 30g per 100mL in cold methanol, whereas its solubility in water is 7.2g per at 95 degrees Celsius and 0.22g per 100mL at 2 degrees Celsius. Which solvent would be …
  4. Organic Chemistry

    Would it be possible to separate hexane (b.p. 68.95 degrees Celsius) from toluene (b.p. 110.6 degrees Celsius) by simple distillation?
  5. physical scince

    answer the following question: QUESTION 4: What does it mean if a compound has a solubility of 15g in 100g of water at 0 degrees Celcius?
  6. Chemistry

    An unknown compound X is one of the four compounds listed in the table below. A mixture of X with o-toluic acid melts at 100 degrees Celsius, a mixture of X with benzoic acid melts at 112 degrees Celsius, a mixture of X with phenyl …
  7. organic chem

    Calculate Percent Composition of the Unknown Mixture : Methanol BP 64.7 Toluene Bp 110.6
  8. Chem Lab Questions

    1. Use the Van der Waals equation to calculate the pressure exerted by 1.00 mol of Cl2; in 22.41 L at 0.0 degrees C. The constants for Cl are a = 6.49 L2 atm/mol2 and b = 0.0526 L/mol. 2. How much potassium chlorate is needed to produce …
  9. organic chemistry

    4. A 300-ml aqueous solution containing 40 g compound A is to be extracted with ether. The solubility of compound A in either at room temperature is 20 g per 100 ml and in water is 13.3 g per 100 ml. calculate the weight of the compound …
  10. Organic Chemistry

    Compound A has solubility at 20 degrees celsius of .029 g / 10.0 mL. How much of compound A will remain in solution after cooling to 20 degrees C?

More Similar Questions

Post a New Question