Caffeine contains C, H, O, N.
If the combustion of 1g Caffeine produces 1.813g Co2 and .4639g H2O and the sample contains .2885g 'N'. Estimate the molecular formula of caffeine using the mas spec of caffeine. (mother ion=194)

Where do i start?

Question

Caffeine contains C, H, O, N. 
If the combustion of 1g Caffeine produces 1.813g Co2 and .4639g H2O and the sample contains .2885g 'N'. Estimate the molecular formula of caffeine using the mas spec of caffeine. (mother ion=194)

Where do i start?

anonymous · Answer

Ok so i figured out the mole of C, H, and N 
C= .0412 mol
H= .0514mol 
N= .02059 mol

But i cant seem to figure out O...
@aaronq  can you please help me

anonymous · Answer

@aaronq can you please help

aaronq · Answer

sorry, i dont get notifications right away, it's something to do with the site.


the moles of O will be half of the moles of $H_2$, because in water there are 2 H's and 1 O.

anonymous · Answer

can you help me with another question @aaronq ?

anonymous · Answer

$$Cu + S_8 \rightarrow ?$$ 
Mass of Cu wire is 1.056g
Mass of crucible is 24.681
Copper Sulfide and crucible is 26.033g so Copper sulfide is 1.352

We have to find the empirical formula, which i know how to do, but for some reason this problem is confusing. me. @aaronq

anonymous · Answer

@paki can you help me?

aaronq · Answer

so find the mass of S (subtract 1.056 from 1.352)

convert both masses (Cu and S) to moles, etc

anonymous · Answer

So i have .0166mol Cu
and .0092mol S

Then you divide buy .0092 which gives the empirical formula of Cu2S, correct?

anonymous · Answer

So the product of Cu + S8 would be Cu2S? Copper (II) sulfide? @aaronq

aaronq · Answer

if that's what the math says, yes

anonymous · Answer

Awesome, thanks :)