Question

When iron rusts, solid iron reacts with gaseous oxygen to form solid iron(III) oxide. Write a balanced chemical equation for this reaction.

Short answer

The balanced chemical equation for the reaction of iron rusting is: 4Fe + 3O₂ → 2Fe₂O₃.

Step-by-step solution

Identify the Reactants and Products

First, identify the reactants and products involved in the reaction. The reactants are solid iron (Fe) and gaseous oxygen (O₂), and the product is solid iron(III) oxide (Fe₂O₃).

Write the Skeleton Equation

Write the unbalanced equation, also known as the skeleton equation, by placing the reactants on the left and the products on the right of an arrow that represents the direction of the reaction. The skeleton equation is: Fe + O₂ → Fe₂O₃.

Balance the Equation

Balance the chemical equation by adjusting the coefficients (the numbers placed in front of the chemical formulas) to have the same number of each type of atom on both sides of the equation. After balancing, the equation is: 4Fe + 3O₂ → 2Fe₂O₃.

Key concepts

Chemical Reactions

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. In the case of iron rusting, the chemical reaction involves the reactants iron (Fe) and oxygen (O₂) transforming into the product iron(III) oxide (Fe₂O₃). The representation of this change is done through a chemical equation that shows the conversion of reactants to products, indicating the substances involved and the changes they undergo.

For students, understanding a chemical reaction starts with recognizing the signs of chemical change, such as color change, temperature change, gas production, or solid formation (precipitate). It's essential to grasp that during these reactions, atoms are neither created nor destroyed; they simply rearrange to form new substances, following the law of conservation of mass.

Stoichiometry

Stoichiometry is a branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It allows us to predict how much product will form from a given amount of reactants or how much reactants are required to form a specific amount of product. This relies on the balanced chemical equation, which provides the mole ratios of reactants and products through its coefficients.

For instance, the balanced chemical equation for iron rusting is: \[ 4Fe + 3O_2 \rightarrow 2Fe_2O_3 \].This indicates that 4 moles of iron react with 3 moles of oxygen to produce 2 moles of iron(III) oxide. Through stoichiometry, if you know the amount of iron you have, you can calculate the amount of iron(III) oxide that will form. Additionally, understanding stoichiometry is essential for further learning in chemistry, like calculating yields, determining limiting reactants, and carrying out titrations.

Oxidation-Reduction Reactions

Oxidation-reduction reactions, also known as redox reactions, involve the transfer of electrons between chemical species. The substance that loses electrons is oxidized, while the one that gains electrons is reduced. In rusting, iron is oxidized by oxygen, which is reduced. Rust formation is a classic example of a redox reaction, where iron (Fe) loses electrons to oxygen (O₂), leading to the creation of iron(III) oxide (Fe₂O₃).

The balanced chemical equation provides insight into the redox process. Iron starts off with a neutral charge but becomes Fe³⁺ in iron(III) oxide due to the loss of three electrons. Meanwhile, oxygen gains those electrons and is reduced. Recognizing redox reactions is fundamental to understanding various chemical processes, including those in batteries, corrosion, and biological systems. It can seem complex, but remember the mnemonic 'OIL RIG': Oxidation Is Loss, Reduction Is Gain.