that's a problem!!!!!

[lousy]

For a certain substance the partition coefficient for ether and water is 3:1
i.e. if an aqueous solution of the substance is shaken with ether, then the substance becomes distributed between the two immiscible liquids in such way that its concentration in ether is 3 times its concentration in water.

a) 200cm^3 of an aqueous solution containing 20g of the substance is shaken with 200cm^3 of ether. Find the amount of the substance extracted by the ether and express it as a fraction of the original amount.

b) 200cm^3 of an aqueous solution containing 20g of the substance is shaken with 100cm^3 of ether. Find the amount of the substance extracted by the ether and write down the fraction remaining in the aqueous phase.


if someone could help me to start this i would appreciate it!

 

[stapel]

a) There are twenty grams of the substance. This needs to be distributed so that the concentration in the ether is three times the concentration in the water. Since the water is 200 cubic centimeters (cc's) and the ether is 200 cc's, then you only need to split the twenty grams into four parts, putting three of the parts into the ether and the remaining part into the water.

b) In this case, the ether and water are in differing amounts. Since you have twice as much water as ether, for the concentration to be as required, you will need twice as many parts of the substance going into the water. That is, instead of three parts into the ether and one part into the water, you'll need three parts into the ether and two parts into the water, so that each 100 cc's of ether gets three parts and each 100 cc's of water gets one part. So use five parts for the substance this time, instead of four.

Hope this helps a bit.

Eliz.

 

[lousy]

thank you stapel, if i put the 3 parts into ether i have 15g. of the substance in ether so do i just do the fraction then? a) 15/20 and then i simplify 3/4


b) i got that the amount extracted by ether is 12g. of the substance and then i dont understand how to find the fraction remaining in the aqueous phase.

thanks again, can you please tell me if these are correct? and help me a bit more on the end of b)???????

 

[lousy]

i got the answer for the previous is 8/20=2/5

can someone please help me with this one????????

the 200cm^3 aqueous phase containing the remaining amount of substance is drawn off and is shaken with a fresh 100cm^3 of ether. find the amount extracted by ether and hence the total amount extracted and express it as a fraction of the original amount.

can someone help??????????????