Question

Why must a chemical equation be balanced? What law is obeyed by a balanced chemical equation?

Short answer

Chemical equations must be balanced to obey the law of conservation of mass.

Step-by-step solution

Understanding Chemical Equations

A chemical equation describes a chemical reaction by using the symbols and formulas of the reactants and products. Each compound is represented by its chemical formula, and the number in front of each formula indicates the quantity of each substance involved in the reaction.

Conservation of Mass

The law of conservation of mass states that in a closed system, mass is neither created nor destroyed during a chemical reaction. This means that the total mass of the reactants must equal the total mass of the products.

Balancing the Equation

To obey the law of conservation of mass, a chemical equation must have the same number of each type of atom on both sides of the equation. This is achieved by adjusting coefficients, the numbers in front of the formulae, to ensure that atom counts are equal for each element.

Checking the Balance

After adjusting the coefficients, it's important to recount the atoms of each element on both sides of the equation to ensure that they match. If they do, the equation is balanced, confirming the reaction respects the law of conservation of mass.

Verifying the Law Obeyed

A balanced chemical equation inherently respects the law of conservation of mass as it reflects equal masses and a constant total number of atoms for both reactants and products.

Key concepts

Chemical Reaction

A chemical reaction is a process where substances, known as reactants, are transformed into new substances called products. During this transformation, the chemical bonds between atoms are broken and reformed to create different arrangements. These changes are often shown using a chemical equation, a concise way to represent the reactants turning into products using symbols. It is essential to understand that although the substances change, the atoms themselves are neither created nor destroyed in the process.

• Reactants: The starting substances in a chemical reaction.
• Products: The new substances formed as a result of the chemical reaction.

Each reaction is unique, but they all follow some fundamental principles, such as maintaining the conservation of mass.

Conservation of Mass

The conservation of mass is a key principle in chemistry stating that mass is neither created nor destroyed in a closed system during a chemical reaction. This means the total mass of the substances before the reaction must be equal to the total mass afterwards. This principle was first put forth by Antoine Lavoisier, a pioneering scientist, who found that the same amount of each type of atom must be present in the products as in the reactants.

When balancing chemical equations, our goal is to ensure that this law is respected. Regardless of the complexity of the chemical reaction, the masses and the number of each type of atom remain unchanged between reactants and products. This is why balancing chemical equations is vital—not just to comply with theoretical principles, but to reflect real-life phenomena accurately.

Chemical Formulas

Chemical formulas are a shorthand way to represent substances in a chemical equation. Each formula consists of symbols from the periodic table to represent the elements involved and subscripts to show the number of atoms of each element in a molecule. By understanding chemical formulas, we can identify the quantities and types of atoms that participate in the reaction.

When a formula appears in a chemical equation, it tells us about both identity and amount, which is essential when balancing the equation. For example:

• Water (H₂O) consists of 2 hydrogen atoms and 1 oxygen atom.
• Carbon dioxide (CO₂) consists of 1 carbon atom and 2 oxygen atoms.

Understanding this representation helps in seeing how elements combine and rearrange during chemical reactions to form new substances, making the balancing act an accurate depiction of what occurs on a molecular level.

Reactants and Products

In a chemical equation, reactants and products are crucial to understanding the transformations happening during a chemical reaction. Reactants are the substances initially present before the reaction begins, and are found on the left side of the equation. Products, which are formed as the reaction occurs, are shown on the right side.

To visualize these transformations, consider the combustion of methane:

• Reactants: Methane (CH₄) and Oxygen (O₂).
• Products: Carbon dioxide (CO₂) and Water (H₂O).

Balancing the equation ensures that each type of atom from the reactants is accounted for in the products, maintaining the law of conservation of mass. This balancing act confirms that the chemical reaction is not just about new product formation, but also about the precise reorganization of atoms from the reactants.