The reaction provided, \(4 \text{Fe} + 3 \text{O}_2 \rightarrow \text{rust}\), indicates that iron (Fe) combines with oxygen (O₂) to form rust. Rust is primarily composed of iron(III) oxide, which is represented as \( \text{Fe}_2\text{O}_3 \).
To apply the law of conservation of mass, the products must have the same number of atoms of each element as the reactants.
In the reaction:
- There are 4 iron atoms (Fe) consumed on the left side.
- On the right side, to balance the iron atoms, we can have \(2 \text{Fe}_2\text{O}_3\), which contains 4 iron atoms (2 × 2 = 4 Fe) and 6 oxygen atoms (2 × 3 = 6 O).
Thus, the product of the reaction can be \(2 \text{Fe}_2\text{O}_3\).
So, in your list of responses, the correct answer for the product of the reaction based on the law of conservation of mass is: 2Fe₂O₃.