Question

Write a chemical equation for iron metal combining with chlorine gas to give yellow ferrous chloride solid.

Short answer

The chemical equation is: Fe (s) + Cl₂ (g) → FeCl₂ (s).

Step-by-step solution

Understand the Reactants and Product

Identify the reactants: iron metal (Fe) and chlorine gas (Cl₂), and the product: ferrous chloride (FeCl₂). Ferrous chloride contains Fe in a +2 oxidation state.

Write a Skeleton Equation

Start by writing the skeleton equation indicating reactants turning into products: \[ \text{Fe (s) + Cl₂ (g) → FeCl₂ (s)} \] This shows iron and chlorine gas reacting to form ferrous chloride.

Balance the Chemical Equation

Ensure the number of atoms of each element is equal on both sides of the equation. Since there are already one iron atom and two chlorine atoms in FeCl₂, the equation is already balanced: \[ \text{Fe (s) + Cl₂ (g) → FeCl₂ (s)} \]

Key concepts

Understanding Reactants and Products

In any chemical reaction, we start by identifying the substances involved. These are the building blocks that undergo the transformation.
Reactants are the starting substances in a chemical reaction. In our example, we have two reactants: iron metal, denoted as \( ext{Fe} \), and chlorine gas, which is represented as \( ext{Cl₂} \). These substances react together in a given reaction.
Products are what the reactants transform into during the reaction. For the reaction between iron and chlorine gas, the product formed is ferrous chloride, or \( ext{FeCl₂} \). This substance has iron in a +2 oxidation state and appears as a yellow solid.
By identifying these key players—the reactants and the products—we set the stage for writing the chemical equation that represents this transformation.

Drafting a Skeleton Equation

A chemical equation is like a sentence describing a chemical reaction.
The skeleton equation acts as the preliminary draft of the chemical equation, where we jot down the formulas of the reactants and the products. It is one of the simplest forms of chemical equations, showing how substances start and finish, but not yet balanced.
In our example, when iron reacts with chlorine gas, the skeleton equation appears as:
\[ \text{Fe (s) + Cl₂ (g) → FeCl₂ (s)} \]
Here, the symbols "(s)" and "(g)" denote the physical states of the substances, solid and gas respectively. This skeleton equation clearly indicates that iron and chlorine gas are combining to produce ferrous chloride. It becomes our foundational outline before proceeding to balance the atoms involved.

Balancing Chemical Equations

The purpose of balancing a chemical equation is to ensure the conservation of mass in accordance with the law of conservation of mass. This ensures that the number of atoms for each element is the same on both sides of the equation.
For our example equation, initially, we have one iron atom and two chlorine atoms in the reactants. In the product, ferrous chloride (\( ext{FeCl₂} \)), there is one iron atom and two chlorine atoms. Since these numbers match on both sides, our equation is already balanced:
\[ \text{Fe (s) + Cl₂ (g) → FeCl₂ (s)} \]
Balancing chemical equations may require adjusting coefficients (the numbers before molecules) so that they reflect the same quantity of each type of atom before and after the reaction. But, in this particular case, no adjustments are needed because it is already balanced.
Understanding and balancing chemical equations are crucial skills in chemistry as they thereby allow you to predict the proportions of chemicals involved and the products formed.