chemistry
posted by whitney .
Assuming that the volumes of carbon diox
ide and of propane are measured under the
same experimental conditions, what volume
of carbon dioxide is produced by the complete
combustion of 20 L of propane?
i just don't understand

This is just another stoichiometry problem but since everything is a gas and measured at the same conditions, it allows us to use a shortcut.
C3H8 + 5O2 ==> 3CO2 + 4H2O
We may use volume in liters as if L = mols. Simply convert L C3H8 to L CO2 using the coefficients in the balanced equation.
20 L C3H8 x (3 mol CO2/1 mol C3H8)= 20 x (3/1) = 60 L CO2.