[Luddus]

Hi. I have a bit of a conondrum. Its probably easy to find out, but i cant for the life of me understand how. Here Goes:

I have an unknown hydrocarbon (CxHx) being incinerated with a surpluss of oxygen. From the incineration i am left with 206,4mg of CO2 and 56,2mg of H2O.

What is the empirical formula for the hydrocarbon and how can i calculate this?

[Hunter2]

Get the moles of water and carbondioxide, these correspond to the moles of C and H.
Then compare both and get ratio with both.

[Luddus]

Thank you very much!

It should be something like this then?

206,4g*10-3/44,01g/mol=4,689*10-3mol
56,2g*10-3/18,01g/mol=3,12*10-3
CxHy +O2 -> CO2 + H2O
Cx/Hy= 4,689*10-3mol/3,12*10-3mol=1,50
CH1,5
C2H3

[Borek]

56,2g*10-3/18,01g/mol=3,12*10-3

3.12×10^-3 of what?

[Luddus]

my bad, it should say 3,12*10^-3mol

[Hunter2]

But that is not the question. Recheck moles of H. How many moles H you have, if you have 1 mol H2O.

[Luddus]

i would still have two moles of H, right?

[Hunter2]

 Yes, so what does it mean for your exercise value.

[Luddus]

i would have to double my H value? thus getting C2H6?

[Hunter2]

No

You have 4,68  x10^-3 C and 6,24 × 10^-3 H
This number you have to convert to unbroken number.
Start convert C to 1. What is the result for H then.
If you have that continue to multiply until both unbroken.

[Luddus]

i am not sure, but taking the %weight of each atom and converting it to moles gave me 0,006 moles of H, 0,01 moles of O and 0,0046 moles of C. I am not sure how to proceed from this though

[Hunter2]

No


4,68  x10^-3 C and 6,24 × 10^-3 H
1 C to  6,24×10^-3/4,68x10^-3 H means
1 C to 1,33333 H
Now calculate further that you dont have broken number of H

[Luddus]

did you switch up your numbers? You have different values on line 1 and 2

[Hunter2]

What do you mean.
You have xC and yH

C = y/x* H

[Luddus]

No


4,68  x10^-3 C and 6,24 × 10^-3 H
1 C to  6,24×10^-3/4,68x10^-3 H means
1 C to 1,33333 H
Now calculate further that you dont have broken number of H

you have 4,68 x10^-3 C on the first line, and on the second you have 6,24x10^-3 on the second. I'm just a little confused, but thank you so very musch for your help, i really appreaciate it!