The minimum amount of O2 (g) consumed per gram of reactant is for the reaction:
(Given atomic mass: Fe = 56, O = 16, Mg = 24, P = 31, C = 12, H = 1)1
4Fe (s) + 3O2 (g) → 2Fe2O3 (s)
2
P4 (s) + 5O2 (g) → P4O10 (s)
3
C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (I)
4
2Mg (s) + O2 (g) → 2MgO (s)