Propane a fuel that is used in camp stoves produces carbon dioxide and water vapor on combustion follows given that the molar mass of h2o is 18.02g/mol how many liters of propane are required at sfo to produce 75g of h2o from this reaction

find the number of moles of H2O using the molar mass of H2O 

moles of H2O = 75g/18.02 g/mol = 4.162 moles 

go between the H2O and the propane to find the mole of propane

4.162 moles H2O its a 1 : 4 ratio so divide 4.162 / 4 = 1.041mol of propane

use this equation to find the volume of gas required : V = nRT/P

n is the moles of gas (propane)

R is the universal gas constant (0.082057338)

T is the temperature of the gas (273K)

V = (1.041) x (0.08206 L-atm/mol-K) x (273K)/(1 atm)

V = 23.3 L of C3H8

hope that helps

it means there are 3 atoms of oxygen