Chemistry combustion analysis gas problem

[Nellen2222]

Homework Statement

Complete combustion of a 0.0150 mol sample of a hydrocarbon, CxHy, gives 1.680L of CO2 at STP and 0.810g of H2O
a) what is the molecular formula
b) what is empirical formula

Homework Equations

pv=nRt

The Attempt at a Solution

a) mol of co2: n=pv/Rt=1 atm * 1.680L/0.0821*273= 0.074955495mol

- Mol of h2o: 0.810g/18.02g/mol * 2 = 0.08990011 mol H2

mol ratio: 0.08990011/0.074955495= 1.199379845... * 5 = 6

molecular formula: c5h6.

Is this wrong? is it possible to multiply by four and round the number to 5 instead of 6? so that it would be c4h5? Or is the above one correct?also: how do i get the molecular formula? i can't get a lowest whole number ratio here.
Thanks!

 

[chemisttree]

Looks good to me provided you did the math correctly. Could also be C10H12 or C15H18...

 

[Borek]

0.0150 mol sample of a hydrocarbon

Could also be C10H12 or C15H18...

C₅H₆ it is, OP started with the number of moles.

 

[chemisttree]

Argh! That should have been Nellen's reply.

 

[Borek]

Oops.