# what is the total combined mass of carbon dioxide and water that is produced?

I always get stuck on story problems....please help, I'm not sure what to do with this...........                     An auto gas tank holds 42kg of gasonline. when the gasoline burns, 168kg of oxygen are consumed and carbon dioxide and water are produced. What is the total combined mass of carbon dioxide and water that is produced??

### first write the balanced

first write the balanced equation;

2 C8H18 + 25 O2 → 16 CO2 + 18 H2O

now this equation gives you a very important info that 2 moles of octane burns in presence of 25 moles of O2  to produce 16 moles of CO2 ad 18 moles of H2O .

so, when 168 kg of O2 are consumed how much CO2 and water will produced this is something that you could using mole- mole ratio.

first convert 168 kg O2 to moles , using;

kg -----> g ------> moles, lets say you get x moles of O2

then, use conversion factor;

25 moles of O2 = 16 moles of CO2

so, x moles of O2 will produce?

x moles of O2 *   16 moles of CO2 / 25 moles of O2 = ? moles of CO2

do the same thing with O2

then convert the moles to mass in grams and grams to kgs, add the masses of CO2 and H2O to get your final answer.