Final answer:
The correct coefficient for Cl2 when balancing the equation Fe + Cl2 → FeCl3 is 3. This ensures that the equation has equal numbers of both Fe and Cl atoms on both sides, satisfying the law of conservation of mass.
Step-by-step explanation:
When balancing the chemical equation Fe + Cl2 → FeCl3, we need to ensure that the number of atoms of each element is the same on both sides of the equation. This is a requirement of the law of conservation of mass. The unbalanced reaction suggests that iron (Fe) reacts with chlorine gas (Cl2) to form iron(III) chloride (FeCl3).
Iron(III) chloride contains iron with a charge of +3, which is indicated by the 3 in FeCl3, and there are three chloride ions, each with a charge of -1, to balance out the charge of iron. This means we need one Fe atom and three Cl atoms to form one molecule of FeCl3. Therefore, if we write a coefficient of 3 in front of the Cl2 and a resulting coefficient of 2 in front of the FeCl3, we get:
2 Fe + 3 Cl2 → 2 FeCl3
This ensures that we have 2 Fe atoms on both sides of the equation and 6 Cl atoms on both sides as well (3 Cl2 molecules times 2 Cl atoms per molecule). The balanced equation indicates that the coefficient for Cl2 is 3.