IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: aiyla on October 25, 2009, 03:59:35 pm

Title: chemistry moles help please ?
Post by: aiyla on October 25, 2009, 03:59:35 pm

Concentration of cholesterol C27H4O6 in a patients blood was found to be 6 millimole
a. find the concentration in mole/dm3
b. find the concentration in grams/dm3
c. what is the mass of cholesterol in 10cm3 of the patients blood .


please if some one can answer this ,, its not much .. cud u like show what formula;s you used ?

Title: Re: chemistry moles help please ?
Post by: @d!_†oX!© on October 25, 2009, 04:15:50 pm

Quote from: aiyla on October 25, 2009, 03:59:35 pm

Concentration of cholesterol C27H4O6 in a patients blood was found to be 6 millimole
a. find the concentration in mole/dm3
b. find the concentration in grams/dm3
c. what is the mass of cholesterol in 10cm3 of the patients blood .


please if some one can answer this ,, its not much .. cud u like show what formula;s you used ?

can u check the question plss
i think the question should be 6 millimole per dm^3 (or litre or cm^3 cuz d concentration cannot be just 6 millimoles)
check the question and let me know

Title: Re: chemistry moles help please ?
Post by: nid404 on October 25, 2009, 04:26:12 pm

Is it 6 millimolar ???

Title: Re: chemistry moles help please ?
Post by: aiyla on October 25, 2009, 04:44:36 pm

yes its 6 millimole per dm^3

Title: Re: chemistry moles help please ?
Post by: nid404 on October 25, 2009, 04:47:57 pm

I assume it is millimolar.
So u get millimolar=10-3 molar
1 molar= 1mol/l
1l=1dm3
therefore
 a)6 millimolar= 0.006 molar or mol/dm3
b)1 mole= 27X12 + 4 + 6X16=424g
therefore 0.006moles/dm3 = 0.006X424g/dm3
c)conc is 0.006mol/dm3. volume=10cm3 which is 0.01dm3
conc=mole/vol
moles=concXvol
so no of moles of cholestrol in 0.01dm3 are 6X10^-5

hope this helps :)
therefore mass is 6X10^-5 X 424

Title: Re: chemistry moles help please ?
Post by: aiyla on October 25, 2009, 05:08:20 pm

thanks aalot ... thats the way i wanted it ..

but in the end u multiplied by 242 instead of 424



<3

Title: Re: chemistry moles help please ?
Post by: nid404 on October 25, 2009, 05:12:37 pm

Quote from: aiyla on October 25, 2009, 05:08:20 pm

thanks aalot ... thats the way i wanted it ..

but in the end u multiplied by 242 instead of 424



<3

oh im sorry abt that...haste leads to waste...I'll edit my post

Title: Re: chemistry moles help please ?
Post by: aiyla on October 25, 2009, 05:40:24 pm

how did u convert 6 millimolar to 0.006 mol/dm3

i dont get that part ):

Title: Re: chemistry moles help please ?
Post by: aiyla on October 25, 2009, 05:48:47 pm

i got the first part ,, but here this in the second one

0.006X424g/dm3

why did we multiply instead of divide ? 
to find g/dm^3  isnt it  .. mass of solute/volume of solution  ????

Title: Re: chemistry moles help please ?
Post by: nid404 on October 25, 2009, 06:45:56 pm

Quote from: aiyla on October 25, 2009, 05:48:47 pm

i got the first part ,, but here this in the second one

0.006X424g/dm3

why did we multiply instead of divide ? 
to find g/dm^3  isnt it  .. mass of solute/volume of solution  ????

we r simply converting moles to gms. so u just multiply the moles by the mass of 1 mole.

mass= no.of moles X molar mass