Question

Iron reacts with atmospheric oxygen to form

Answer 1

Iron reacts with atmospheric oxygen and water to form rust, or hydrated iron (III) oxide. The rust formed does not protect the metal, leading to continuous corrosion of iron as the rust flakes off.

Step-by-step explanation:

Iron reacts with atmospheric oxygen to form a compound commonly known as rust. This process occurs in two main steps. Initially, iron is oxidized to iron (II) ions (Fe2+ (aq)) by oxygen. Following this, iron (II) ions are further oxidized in the presence of water and oxygen gas to produce hydrated iron (III) oxide, or rust. The chemical reaction can be summarized as:

• 
  
• 2 Fe(s) + O2(g) + 4 H+ (aq) → 2 Fe2+ (aq) + 2 H2O(l)
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• 4 Fe2+ (aq) + O2(g) + (4 + 2x)H2O(l) → 2 Fe2O3 · xH2O(s) + 8 H+ (aq)

The formation of rust involves the oxidation of iron in the presence of water and atmospheric oxygen. Rust is chemically Fe2O3·xH2O where x represents the number of water molecules which varies. Unlike other metals such as copper, which form a protective patina, rust does not protect the underlying iron from further corrosion. This is why rusted iron continues to deteriorate as the flaky rust exposes fresh metal to the environment, allowing the corrosion process to continue.