# Hydrocarbon empirical formula question

## Homework Statement

Q. A Hydrocarbon (CnHm) is burned completely in oxygen to produce a mixture of CO2 and H2O. The total pressure of mixture is 1.200 atm and partial pressure of H2O is 0.686 atm. What is empirical formula of Hydrocarbon

## Homework Equations

pV=nRT
pa/ptotal = na/ntotal

## The Attempt at a Solution

The answer is C3H8 aka Propane

Im so confused! I don't even know where to start with this!!