Under anaerobic conditions, hemoglobin (HbFe²⁺) can react with nitrite to form methemoglobin (HbFe³⁺).HbFe²⁺ + NO₂⁻ + 2H⁺ → HbFe³⁺ + NO + H₂OWhich element is reduced in the reaction?

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11ecba2d_1201_6a9a_a3bf_ab8a68f88607_MD0008_00 In a redox reaction, oxidation and reduction always occur together. An atom is reduced by gaining one or more electrons, but this is possible only if another atom loses the electrons (gets oxidized). As a means of tracking the gain or loss of electrons by atoms in reactions, an oxidation number (oxidation state) is assessed for each atom in a compound relative to the number of electrons in a neutral atom of that element. Oxidation numbers may be assessed using Lewis structures; however, for compounds in which all atoms of a given element have equivalent states, values may be alternatively found by using the compound formula and oxidation state rules. In this alternate method, atoms with consistent oxidation states (those that rarely vary) are used to determine oxidation states for atoms that have variable states (such as metals). Using the oxidation state rules to assign oxidation numbers to each atom in the chemical formulas of the reaction equation shows that the oxidation state of nitrogen decreases from +3 to +2. This shows that nitrogen is gaining a negatively charged electron and is being reduced. (Choice A) The oxidation state of iron increases from +2 to +3. This means that iron is losing a negatively charged electron and is being oxidized rather than being reduced. (Choices C and D) The oxidation states of oxygen and hydrogen do not change; therefore, these elements do not undergo oxidation or reduction. Educational objective: Using oxidation state rules, the oxidation number of each atom in a compound formula may be determined and used to track the gain (reduction) or loss (oxidation) of electrons of an atom in a redox reaction.

Under Anaerobic Conditions, Hemoglobin (HbFe2+) Can React with Nitrite to Form

Under Anaerobic Conditions, Hemoglobin (HbFe²⁺) Can React with Nitrite to Form