To burn 1 molecule of c9h20 to form co2 and h2o (complete combustion), how many molecules of o2 are required?

14 oxygen molecules First, count the number of carbon and hydrogen are in the original molecule of c9h20 9 carbon. 20 hydrogen. Each carbon atom will make 1 molecule of CO2 and will require 2 oxygen atoms per molecule, so multiply 9 by 2 to get the number of oxygen atoms needed. 9 * 2 = 18 It takes 2 hydrogen atoms to make a water molecule and it takes 1 oxygen atom. So divide the number of hydrogen atoms by 2 to get the number of water molecules you can make. 20 / 2 = 10 So you need a total of 18 plus 10 oxygen atoms giving a total of 18+10 = 28 oxygen atoms. But you don't want to know the number of oxygen atoms, you want to know the number of oxygen molecules. Since there's 2 oxygen atoms per oxygen molecule, just divide by 2. Giving 28 / 2 = 14 Therefore you need 14 oxygen molecules for full combustion of 1 C9H20 molecule.