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) 4 Fe(s) + 3 O₂(g) → 2 Fe₂O₃(s)
(2) P₄(s) + 5 O₂(g) → P₄O10(s)
(3) C₃H8(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(l)
(4) 2Mg(s) + O₂(g) →MgO(s)