A CHEMISTRY QUESTION!!! PLEASE HELP?

N

Nikki

New member
heres the question:

Isopropyl alcohol is composed of C, H, O. compustion of 0.255 g of isopropyl alcohol produces 0.561 g CO2 and 0.306g H2O.

a.) what is the empirical formula?

b.) if the molar mass= 60g/mol, what is the molecular formula?
 
We seem to have to work backwards for this problem. The first thing we need to do is determine the number of moles for both CO2 and H2O.
Molar Mass CO2 = 44.0098g/mol
0.561g CO2 / 44.0098g/mol CO2 = 0.0127mol CO2
Molar Mass H2O =18.01528g/mol
0.306g H2O / 18.01528g/mol H2O = 0.0170mol H2O
0.0170mol H2O / 0.0127mol CO2 = 1.3325
There is a 1.3325:1 ratio H2O:CO2 which makes it 4:3
The products of the reaction would be 3CO2 + 4H2O, giving us the formula of C3H8O10
Now, I know what isopropyl alcohol is and I can tell you it's C3H8O not C3H8O10. I've done the math several times and double checked and what not but that's what I get. The only way I can explain this is the reaction must've occurred under an excess of oxygen. C3H8O is also the molecular formula. I'm sorry I can't be more help.
 
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