Comparing interaction of diluted and concentrated sulfuric acid with iron

Sulfuric acid (H₂SO₄) is a strong acid that can interact with iron to form iron(III) sulfate (Fe₂(SO₄)₃) and hydrogen gas (H₂). The extent and rate of this reaction depend on the concentration of the sulfuric acid.

Method of electron balance: This method involves balancing the number of electrons lost and gained by each species involved in the reaction in order to determine the oxidizing and reducing agents.

Reaction: 2Fe + 3H₂SO₄ → Fe₂(SO₄)₃ + 3H₂

Electron balances: Since iron (Fe) is oxidized from 0 to +3, it loses 3 electrons, making it the reducing agent. On the other hand, each sulfur atom (S) in sulfuric acid gains 2 electrons, reducing from +6 to +4. This makes the sulfuric acid the oxidizing agent.

Oxidation process: Iron atoms lose electrons, increasing their oxidation state from 0 to +3, and forming iron(III) ions (Fe³⁺).

Reduction process: Sulfur atoms gain electrons, reducing their oxidation state from +6 to +4, and forming sulfate ions (SO₄^2-).

Conclusion: Diluted sulfuric acid has a lower concentration of acid molecules per unit of volume compared to concentrated sulfuric acid. Therefore, there are fewer sulfur atoms for iron to interact with in diluted acid. This results in a slower and less intense reaction between sulfuric acid and iron compared to concentrated acid. Furthermore, the oxidizing and reducing agents for this reaction are iron and sulfuric acid, respectively.