In the reaction Fe + 4H2O → Fe3O4 + 4H2, what coefficient must be placed in front of Fe to balance the equation?

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Multiple Choice

In the reaction Fe + 4H2O → Fe3O4 + 4H2, what coefficient must be placed in front of Fe to balance the equation?

Explanation:
Conservation of atoms is the key. Fe3O4 contains three iron atoms per formula unit, so to balance iron you must supply three Fe on the left. Placing a 3 in front of Fe gives: 3 Fe + 4 H2O → Fe3O4 + 4 H2. Checking the other elements confirms balance: hydrogen comes from 4 H2O as 8 hydrogens, matching 4 H2 on the right; oxygen from 4 H2O is 4 oxygens, matching Fe3O4’s 4 oxygens. So the required coefficient is 3.

Conservation of atoms is the key. Fe3O4 contains three iron atoms per formula unit, so to balance iron you must supply three Fe on the left. Placing a 3 in front of Fe gives: 3 Fe + 4 H2O → Fe3O4 + 4 H2. Checking the other elements confirms balance: hydrogen comes from 4 H2O as 8 hydrogens, matching 4 H2 on the right; oxygen from 4 H2O is 4 oxygens, matching Fe3O4’s 4 oxygens. So the required coefficient is 3.

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