# chemistry

posted by .

Ibuprofen, the active ingredient in advil, is made up of carbon, hydrogen, and oxygen atoms. When a sample of ibuprofen, weighing 5.000 g, burns in oxygen, 13.86 g of CO2 and 3.926 g of water are obtained. What is the simplest formula of ibuprofen?

My work:
13.86 g CO2/ 12.01 g C= 1.15 g C
3.926 g H2O/ 2.02 = 1.94 g H
13.86 g CO2 + 3.926 g H2O = 17.48sub6 g products
17.48sub6 g - 3.09 = 14.40 g O
1.15 g C x 1mol/12.01 g= .0957sub5 mol C
1.94 g H x 1mol/1.01 g= 1.92sub0 mol H
14.40 g O x 1mol/16.00= .9000 mol O
divide all by .0957sub5...
the formula comes out to C10H201O94
My problem is, the 14.40 g O isn't just the oxygen in the ibuprofen, but the oxygen in the combustion as well. how do I find out just what's in the ibuprofen so I get the correct formula?

To get the grams of C in CO2, find the fraction of C in CO2, which is 12/(12+2*16)= 12/40
Then, grams C= 13.86 * 12/40 g C
then moles C= gramsC/12

Do the same with H.
Then, to find O, add the grams H and grams C, subtract them from 5.000. Then figure the grams O, and moles O.

Now, having moles of all, do this.
moles C xxxx
moles H yyyy
moles O zzzz

take the smallest of the three numbers, and divide it into all the numbers to get a whole number ratio.

example
moles C 4.53
moles H 9.05
moles O 12.22

divide all by 4.53
moles C 1
moles H 2
moles O 3
CH2O3 in this example. Here is another more complicated:
moles C 4.53
moles H 11.35
moles O 12.22
divide,
moles C 1
moles H 2.5
moles O 3
Now here, to get a whole number ratio , double the numbers..
moles C 2
moles H 5
moles O 6
C2H5O6

Thank you, I assumed something was wrong when I didn't end up using the 5.000 g in my calculation.
I've used this set-up before, and for this problem after doing it this way, I received C101H70O20. This doesn't seem right to me. I think any error I have might have occurred around here:
moles C= .3149sub 2
moles H= .217sub 8
moles O= .0623sub 6
I divided everything by .0623sub 6 [smallest number] and got
moles C= 5.05
moles H= 3.5
moles O= 1
and multiplied everything by 20 to get a whole number ratio.
The molar masses I used for all my calculations:
12.01 g/mol = C
1.01 g/mol = H
16.00 g/mol = O
Did I make an error, or is this correct?

Thank you, I assumed something was wrong when I didn't end up using the 5.000 g in my calculation.
I've used this set-up before, and for this problem after doing it this way, I received C101H70O20. This doesn't seem right to me. I think any error I have might have occurred around here:
moles C= .3149sub 2 OK to here,
moles H= .217sub 8 There are 2 mols H in H2O. This will change mols H as well as grams H AND grams oxygen.
moles O= .0623sub 6
I divided everything by .0623sub 6 [smallest number] and got
moles C= 5.05
moles H= 3.5
moles O= 1
and multiplied everything by 20 to get a whole number ratio.
The molar masses I used for all my calculations:
12.01 g/mol = C
1.01 g/mol = H
16.00 g/mol = O
Did I make an error, or is this correct?

• chemistry -

im getting that the moles C = .347
moles H = .436
moles O = 0.025

and getting a formula of C14H17O
However, i looked it up on wiki and saw that the formula for ibuprofen is in fact i C13H18O2.
the C/H discrepancy is understandable, but the O2 to O is not. Could i have missed something that leads to a doubling of the moles O?

## Similar Questions

1. ### chemistry

a carbon containing 3 atoms of carbon and 8 atoms of hydrdren combinend in reactionwith oxygen molecules the 2 end products of this equation are carbon dioxide co 2 an water what element should i look at first inn this oxygen hydrogen …
2. ### Chemistry

A compound containg 3 atoms of carbon and 8 atoms of hydrogen is combined in a reaction with oxygen molecules. The two end products of this equation are carbon dioxide (CO2) and water. What element should you look at first in balancing …
3. ### Chemistry

A compound containg 3 atoms of carbon and 8 atoms of hydrogen is combined in a reaction with oxygen molecules. The two end products of this equation are carbon dioxide (CO2) and water. What element should you look at first in balancing …
4. ### chemistry

Ibuprofen, the active ingredient in Advil, is made up of carbon, hydrogen, and oxygen atoms. When a sample of ibuprofen, weighing 5.000 g, burns in oxygen, 13.86g of CO2 and 3.926 g of water are obtained. What is the simplest formula …
5. ### chemistry

This is for organic chem lab. I don't understand how to calculate the relative Rf values by setting ibuprofen to 1.00. For example, my Rf value for aspirin is 0.046, so how do I calculate the Rf relative to ibuprofen (1.00)?
6. ### science

Hydrogen burns with blue flame.Oxygen support burning when two atoms of Hydrogen combines with one atom of oxygen forms water this water put off the flames why?
7. ### Chemistry

A compound containing 3 atoms of carbon and 8 atoms of hydrogen is combined in a reaction with oxygen molecules. The two end products of this equation are carbon dioxide and water. What element should you look at first in balancing …
8. ### Intro. Chemistry

Based on the law of definite composition, Dalton proposed that one atom of carbon combines with two atoms of oxygen to always produce CO2. Similarly,he proposed that two atoms of hydrogen combine with one atom of oxygen to give a molecule …
9. ### Chemistry

Using the compound for Ibuprofen C13H18O2 find molecules of Ibuprofen that contain 2.84 x10 23 atoms of Hydrogen So for every 1 mol of H= 6.022 x 10 23 molecules of H?
10. ### Chemistry

Test corrections :) They're calculations/short answers. I'd just like something to compare answers to or help me get the full answer (all partial credits). Thanks! #9. When water is electrolyzed it produces hydrogen and oxygen. If …

More Similar Questions