Answer:
18.
Step-by-step explanation:
1) according to the reaction (M(Fe)=56; M(O₂)=32; V₀=22.4):
4Fe+3O₂⇒2Fe₂O₃; - ν(O₂)=0.75*ν(Fe);
2) ν(Fe)=m(Fe)/M(Fe)=60/56≈1.071 [mol];
3) ν(O₂)=0.75*1.071=0.804 [mol];
4) V(O₂)=V₀*ν(O₂); ⇒ V(O₂)=22.4*0.804=18 [lit].