chem
posted by wll.i.am .
a simple hwk question.. i don't understand what i need to do..
1butanol (shown below) burns in the presence of oxygen to give off carbon dioxide and water by the following reaction:
C4H9OH + 6 O2 ==> 4 CO2 + 5 H2O
If 40.88 mL of 1butanol burns completely, how many grams of 1butanol have burned? grams
(Hint: The density of 1butanol is 0.810 g/mL)

You only have to solve for the mass; everything else is irrelevant to the answer. I hate it when teachers give you a bunch of extra information that you do not need to solve a straight forward problem.
Density=mass/volume
So, solve for mass
density *volume=mass=(0.810g/mL)*(40.88mL)=33.1g of 1butanol
notice that the mL's cancel out and you are only left with grams (g). 
wait okay I figured it out till there... but then later I got this question and got stuck
How many moles of 1butanol does this number of grams represent? 
mols = grams/molar mass