Consider the unbalanced equation for the combustion of butane: $$ \mathrm{C}_{4} \mathrm{H}_{10}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g) $$ Balance the equation and determine how many moles of \(\mathrm{O}_{2}\) are required to react completely with \(4.9 \mathrm{~mol}\) of \(\mathrm{C}_{4} \mathrm{H}_{10}\).

Stoichiometry is the section of chemistry that involves calculating the quantities of reactants and products in chemical reactions. It's a foundational concept for understanding how to balance chemical equations and to predict the outcomes of reactions quantitatively. In a balanced chemical equation, the number of atoms for each element must be the same on both sides, respecting the law of conservation of mass. This balance is essential because it reflects the precise proportion of reactants that will combine to form products.
Stoichiometry relies on the mole concept, as it allows chemists to count atoms, molecules, or ions in a given mass of a substance. Utilizing the mole ratio from the balanced equation, one can calculate the amount of reactants required to produce a desired amount of product, or vice versa. For instance, in the combustion of butane, stoichiometry helps us understand how many moles of oxygen would react with a given amount of butane to produce carbon dioxide and water.

Mole calculation is integral to stoichiometry as it connects the microscopic world of atoms and molecules to the macroscopic quantities that can be measured in the laboratory. A mole is defined as a unit that represents approximately 6.022 x 10²³ particles, which is Avogadro's number. This large constant provides a bridge between the atomic scale and the real-world scale.
To perform mole calculations in a chemical equation, you need the molar masses of the substances involved, which are typically found on the periodic table. By using the molar mass as a conversion factor, you can switch between the mass of a substance and the amount in moles. This process is critical when determining ingredients for a reaction or analyzing product yields—and it was precisely used in calculating the moles of oxygen needed to react with butane in our exercise.

Components of Combustion

A combustion reaction is a chemical process that occurs when a substance (typically a hydrocarbon) reacts with oxygen to produce energy in the form of heat and light. The general formula for a hydrocarbon combustion reaction is: Hydrocarbon + Oxygen → Carbon Dioxide + Water. These reactions are exothermic, meaning they release energy.

Characteristics and Applications

Combustion of fuel, like butane in this exercise, is a practical application of chemistry in everyday life, powering engines, heaters, and stoves. Correctly balancing a combustion reaction is important for predicting the amounts of products formed and for ensuring a reaction goes to completion with no excess reactants.

Understanding chemical reaction quantities is essential when it comes to predicting how much of each substance is involved in a chemical reaction. When you balance a chemical equation, you are effectively setting the stage to calculate these quantities. The coefficients in the balanced equation give you the mole ratio of reactants to products.
For example, if you need to find out how much carbon dioxide will be produced after burning a known amount of butane, you look at the balanced chemical equation. In the combustion reaction from the exercise, a 2:13 ratio of butane to oxygen is established. This means that for every 2 moles of butane, 13 moles of oxygen are required. It is important to note that the quantities generated or consumed in a reaction are constrained by the limiting reactant, which in this case is the butane, as you are calculating how much oxygen is needed to react with a specific amount of butane.