1) Compounds:
Propane: CH3CH2CH3 or C3H8
Oxygen needed for comustion: O2
Carbon dioxide: CO2
Water: H2O
Note: any number to the right of an element is a subscript.
2) Chemical reaction:
C3H8 + 5O2 ----> 3CO2 + 4H2O
3) molar ratios:
1 mol C3H8 : 5 moles O2 : 3 moles CO2 : 4 moles H2O
Answer: 5 moles of O2 is needed for the reaction (combustion of 1 mol of propane)