Propane reacts with oxygen to produce \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\), as shown in the balanced equation: $$ \mathrm{C}_{3} \mathrm{H}_{8}+5 \mathrm{O}_{2} \rightarrow 3 \mathrm{CO}_{2}+4 \mathrm{H}_{2} \mathrm{O} $$ Write this reaction in words using the word mole(s) four times.

Stoichiometry is the branch of chemistry that provides the quantitative relationship between reactants and products in a chemical reaction. It involves calculations that rely on the mole concept to determine the amount of substances that are consumed and produced in a reaction.

Educational exercises focus on understanding these relationships and often involve calculations. For instance, in practice, one might need to find out how much product will result from a certain amount of reactants or vice versa. This ties directly into the law of conservation of mass, which states that matter cannot be created nor destroyed in a chemical reaction, ensuring that the amount of matter remains constant.

The mole concept is a fundamental principle in chemistry that allows chemists to count particles at the atomic level using the unit 'mole.' One mole is defined as the amount of substance containing as many particles (atoms, molecules, ions, or electrons) as there are atoms in 12 grams of carbon-12, which is approximately 6.022 x 10^23 particles, known as Avogadro's number.

In stoichiometric calculations, the mole concept is used to convert between mass and number of moles, and vice versa, with the help of the molar mass of substances.

A balanced chemical equation accurately represents the conservation of matter. It ensures that the number of atoms of each element is the same on both the reactant and product sides of a chemical reaction. This is crucial because it allows for the stoichiometric calculations to be accurate.

The coefficients in a balanced equation, like the '5 moles of oxygen' and '3 moles of carbon dioxide' from our example with propane, represent the relative amounts of moles of each substance involved in the reaction. These coefficients are essential in stoichiometric calculations and help to establish molar ratios between reactants and products.

Combustion reactions are a type of chemical reaction where a substance combines with oxygen and releases energy in the form of light or heat. These are exothermic reactions, meaning they give off heat. The general form of a combustion reaction typically involves a hydrocarbon reacting with oxygen to produce carbon dioxide and water.

Stoichiometry becomes especially important in combustion reactions to calculate the amount of reactants needed to ensure complete combustion, preventing the formation of harmful byproducts, and to calculate the amount of energy released in the process.