Chemical Formulas and Equations: A Comprehensive Overview

Chemical Formulas

Definition and Types

A chemical formula expresses the composition of a substance, both qualitatively and quantitatively. It shows the elements forming the substance and the proportions of their atoms.

There are three main types of chemical formulas:

• Empirical Formula: Provides qualitative and relative quantitative information. It shows the elements and their relative proportions in the substance.
• Molecular Formula: Indicates the exact number of atoms of each element in a molecule.
• Structural Formula: Shows the distribution of atoms in the molecule and the types of bonds between them. Commonly used for organic compounds.

Determining Empirical and Molecular Formulas

The empirical formula is determined through quantitative analysis. By knowing the mass of each element in a sample, we can calculate:

1. The number of moles of each element.
2. The proportion of moles relative to the element with the smallest number of moles.

These proportions, expressed as small whole numbers, become the subscripts in the formula.

Chemical Equations

Representation and Basis

Chemical reactions are represented by chemical equations, which reflect all substances involved qualitatively and quantitatively.

Chemical equations are based on the Law of Conservation of Mass. This law states that the total mass of reactants equals the total mass of products in a chemical reaction.

Balancing Equations

Based on the law of conservation of mass, chemical equations must have the same number of atoms of each element on both sides. This is achieved by introducing coefficients, which represent the number of moles of each substance involved.

While coefficients can sometimes represent the number of molecules, they generally indicate the number of moles.