Stoichiometry

Stoichiometry

Combustion reaction of methane

Stoichiometry is a branch of chemistry that deals with the quantitative relationships between the amounts of reactants and products in a chemical reaction. It is based on the law of conservation of mass, which states that matter is neither created nor destroyed in a chemical reaction. Stoichiometry allows chemists to predict the quantities of substances consumed and produced in a given reaction.

Basic Concepts

Stoichiometry involves several key concepts, including:

Mole Concept

The mole is a fundamental unit in chemistry that represents a specific number of particles, usually atoms or molecules. One mole is defined as exactly 6.022 x 10^23 particles, known as Avogadro's number. The mole allows chemists to convert between the mass of a substance and the number of particles it contains.

Balanced Chemical Equations

A chemical equation represents a chemical reaction using symbols and formulas. A balanced chemical equation has the same number of each type of atom on both sides of the equation, reflecting the conservation of mass. Balancing chemical equations is a crucial step in stoichiometry.

Molar Ratios

Molar ratios are derived from the coefficients of a balanced chemical equation. They indicate the proportions of reactants and products involved in the reaction. These ratios are used to calculate the amounts of substances consumed or produced.

Stoichiometric Calculations

Stoichiometric calculations involve using the balanced chemical equation to determine the quantities of reactants and products. The steps typically include:

1. Writing and Balancing the Chemical Equation: Ensure the chemical equation is balanced. 2. Converting Mass to Moles: Use the molar mass of substances to convert between mass and moles. 3. Using Molar Ratios: Apply the molar ratios from the balanced equation to find the moles of other substances. 4. Converting Moles to Mass: Convert moles back to mass if needed.

Example: Combustion of Methane

The combustion of methane is a common example used to illustrate stoichiometry. The balanced chemical equation for the combustion of methane is:

\[ \text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O} \]

In this reaction, one mole of methane reacts with two moles of oxygen to produce one mole of carbon dioxide and two moles of water. Using stoichiometry, one can calculate the amount of oxygen needed to completely combust a given amount of methane, or the amount of carbon dioxide produced.

Related Pages

• Chemical reaction
• Mole (unit)
• Avogadro's number
• Chemical equation
• Conservation of mass