Explanation:
Balanced chemical reaction equation will be as follows.
[tex]2Fe^{2+}(aq) + 2H^{+}(aq) \rightleftharpoons 2Fe^{3+}(aq) + H_{2}(g)[/tex]
In human body, the neutral iron changes into [tex]Fe^{2+}[/tex](aq) cation. There will be an oxidation-half reaction and a reduction-half reaction. Equations for this reaction are as follows.
Oxidation: 2Fe^{2+}(aq) \rightleftharpoons 2Fe^{3+}(aq) + 2e^{-}[/tex] .... (1)
Reduction: [tex]2H^{+}(aq) + 2e^{-} \rightleftharpoons H_{2}(g)[/tex] ...... (2)
On adding both equation (1) and (2), the overall reaction equation will be as follows.
[tex]2Fe^{2+}(aq) + 2H^{+}(aq) \rightleftharpoons 2Fe^{3+}(aq) + H_{2}(g)[/tex]
Therefore, neutral iron is a part of Heme - b group of Hemoglobin and in an aqueous solution it dissolutes as a part of Heme group. Hence, then it becomes an [tex]Fe^{2+}[/tex] cation.