A hydrocarbon is burnt completely to give 3.447g of #sf(CO_2)# and 1.647g of #sf(H_2O)#. What is the empirical formula ?
Your compound's empirical formula is
I'll show you an alternative approach to getting the number of moles of carbon and of hydrogen the hydrocarbon sample contained.
This method uses the percent composition of carbon and of hydrogen in carbon dioxide and water, respectively.
So, you know that the combustion reaction produces 3.447 g of carbon dioxide. If you use the molar mass of carbon and that of carbon dioxide, you can determine the percent composition of carbon in
This means that, for every 100 g of
Do the same for water and hydrogen, but keep in mind that you get 2 hydrogen atoms for every molecule of water.
Since every 100 g of water will contain 11.21 g of hydrogen, your hydrocarbon contained
Now use the molar masses of carbon and hydrogen to determine how many moles of each you have
Once again, divide both numbers by the smallest one to get the mole ratio carbon and hydrogen have in the hydrocarbon
You sample contained
Multiply by 3 to get rid of the fractional subscript
The empirical formula is
Convert moles to grams by dividing by the
So the empirical formula is