To demonstrate the Law of Conservation of Mass, the number of each type of atom must be the same on both sides of the equation. The original equation is:
\( 4 \text{Fe} + \text{O}_2 \rightarrow 2 \text{Fe}_2\text{O}_3 \)
Let's count the atoms:
-
Reactants:
- Fe: 4
- O: 2
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Products:
- Fe: 2 (from \( 2 \text{Fe}_2\text{O}_3 \) since each \( \text{Fe}_2\text{O}_3 \) has 2 Fe, so \( 2 \times 2 = 4 \))
- O: 6 (from \( 2 \text{Fe}_2\text{O}_3 \) since each \( \text{Fe}_2\text{O}_3 \) has 3 O, so \( 2 \times 3 = 6 \))
The equation does not demonstrate the Law of Conservation of Mass because the number of oxygen atoms differs (2 on the reactant side and 6 on the product side).
To balance it, we need to have the same number of O atoms on both sides.
We can change the equation by placing a coefficient of 3 in front of \( \text{O}_2 \):
Corrected Equation: \( 4 \text{Fe} + 3 \text{O}_2 \rightarrow 2 \text{Fe}_2\text{O}_3 \)
Now recounting:
-
Reactants:
- Fe: 4
- O: 6 (from 3 \( \text{O}_2 \))
-
Products:
- Fe: 4 (remains the same)
- O: 6 (remains the same)
With this change, the number of each type of atom is equal on both sides of the equation.
Final answer: On the reactant side, put a 3 in front of O2.