!! LONG ANSWER !!
Your compound's molecular formula is
This one is a little complex because there are many calculations to do before being able to determine the empirical and molecular formulas of the compound.
So, you know that your compound contains carbon, hydrogen, and oxygen. Moreover, you know that a 0.392-g sample occupies a volume of
At STP, one mole of any ideal gas occupies exactly 22.4 L - this is known as the molar volume of a gas at STP. This means that your sample contains
This implies that your compound's molar mass will be
Moving on. You know that this compound undergoes combustion and that 0.32 g of water are produced. You'll use this value to determine how much hydrogen the initial sample contained.
Start by determining the percent composition of hydrogen in water
This means that, for every 100 g of water, you get 11.19 g of hydrogen. Therefore, for 0.32 g, you get
Next, determine how much carbon your initial sample contained. Since the combustion reaction produces
Since you get 1 mole of carbon for every 1 mole of
Use carbon's molar mass to determine how many grams would contain this many moles
You can now figure out how much oxygen your initial sample had by
It's all downhill from here. Calculate how many moles of each element your sample contained by using their molar masses
You compound's empirical formula will be
To get its molecular formula, you have to use the molar mass of the empirical formula and the molar mass of the compound.
Thus, your compound's molecular formula will be
SIDE NOTE You get the same result by using the current definition of STP conditions, at which the volume occupied by an ideal gas is equal to 22.7 L, not 22.4 L.
However, I assume that your problem intended for you to use the old value, so I did the calculations using 22.4 L.