Pre-ap chemistry question! One question, help

C3H8 + 502 ---> 3CO2 + 4H20

If 20 liters of oxygen are consumed in the above reaction, how many liters of carbon dioxide are produced?

Please show me how to do the work so it will help me on the other problems. Thank you.

to do this we have to make assumptions about the pressure and temperature of reactants and reagents, because the volume of a gas (in Liters or whatever) depends on the pressure. Assuming that the pressure is the same before and after, and assuming that the gases will act as ideal gases, then we can remember that 1 mole of any ideal gas has the same volume at a given pressure and temperature.

The stoichiometry of the reaction tells us that for every 5 moles or 5 volumetric units (because 1 mole has the same volume for any ideal gas) or oxygen that you get 3 moles (or three volumetric units) of carbon dioxide.

so, if you have 20 liters of oxygen

and for every 5 liters you get three liters of carbon dioxide

then, 20/5 * 3 = 12

that means 12 liters of CO2 are formed

makes sense?

It takes 5L of oxygen to produce 3L of carbon dioxide.

You want your answer in L CO2, so set the units up to cancel:

3L CO2 20L O2
----------- x --------- = 12L CO2
5L O2. 1

Well, as you can see, the ration of O2 to CO2 is 5 to 3. So, 20 / x = 5 / 3. What would x be?