Final answer:
The number of electrons lost in the reaction 3Fe + 4H₂O → Fe₃O₄ + 4H₂ is 8, as iron atoms go from an oxidation state of 0 to a combined state of d. +8 in the product.
Step-by-step explanation:
The number of electrons lost or gained during the reaction 3Fe + 4H₂O → Fe₃O₄ + 4H₂ can be determined by looking at the oxidation states of Iron (Fe) before and after the reaction. Initially, Fe is in the elemental form so it has an oxidation number of 0. In the product, Fe₃O₄, iron exists in a mixed oxidation state as the compound contains both Fe2+ and Fe3+. Thus, there are two different oxidation states for iron in the product, +2 and +3. As two Fe atoms are in the +3 state and one is in the +2 state, this indicates a total charge of 2(+3) + (+2) = +8 for all the iron atoms combined. From an oxidation state of 0 in the reactants to an average oxidation state of +8/3 per iron atom in the products, it shows that 8 electrons were lost from the 3 iron atoms collectively.
Therefore, the number of electrons lost in the given reaction is d. 8.