Question

Write an equation showing the combustion of propane, \(\mathrm{C}_{3} \mathrm{H}_{8}\). How do we make use of combustion reactions?

Short answer

The balanced chemical equation for the combustion of propane is: \(C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O\). Combustion reactions are crucial for producing heat and energy, which can be utilized for cooking, heating, transportation, and electricity generation, as well as in industrial processes and rocket propulsion.

Step-by-step solution

Write the unbalanced equation

Let's write down the unbalanced chemical equation for the combustion of propane. In combustion reactions, the fuel (in this case, propane) reacts with oxygen gas to produce carbon dioxide and water. C3H8 + O2 → CO2 + H2O

Balance the chemical equation

To balance this equation, we need to ensure that the number of atoms of each element on both sides of the equation is equal. We can adjust the coefficients (the numbers in front of the chemical formulas) until the equation is balanced. C3H8 + 5O2 → 3CO2 + 4H2O Here, the equation is balanced as follows: - 3 carbon atoms in 1 propane molecule (C3H8) equals 3 carbon atoms in 3 CO2 molecules. - 8 hydrogen atoms in 1 propane molecule (C3H8) equals 8 hydrogen atoms in 4 H2O molecules. - 10 oxygen atoms in 5 O2 molecules equals 6 oxygen atoms in 3 CO2 molecules + 4 oxygen atoms in 4 H2O molecules. The balanced chemical equation is: C3H8 + 5O2 → 3CO2 + 4H2O.

Explain the importance of combustion reactions

Combustion reactions are important for several reasons: 1. Energy production: Combustion reactions produce a significant amount of heat and light energy, which can be used for various purposes like cooking, heating, transportation, and electricity generation. 2. Industrial processes: Combustion reactions provide heat needed for various industrial processes such as metal production and chemical synthesis. 3. Rocket propulsion: In rocket engines, combustion reactions provide the high-speed release of energy needed to propel a rocket into space. These are just a few examples of how we make use of combustion reactions in our daily lives and various industries.

Key concepts

Balanced Chemical Equation

Understanding the balance in chemical equations is fundamental for comprehending chemical reactions. A balanced chemical equation has an equal number of atoms of each element on both sides of the reaction. It follows the law of conservation of mass, implying that matter cannot be created or destroyed in a chemical reaction. To balance an equation, one may only adjust the coefficients, which are the numbers placed before the chemical formulas, and not the subscripts, which indicate the number of atoms in a molecule.

For instance, the combustion of propane, represented by the unbalanced equation \( \mathrm{C}_{3}\mathrm{H}_{8} + \mathrm{O}_{2} \rightarrow \mathrm{CO}_{2} + \mathrm{H}_{2}\mathrm{O} \), requires careful adjustment of coefficients to ensure each element's atom count is equal on both sides. It's also essential to balance the elements in a specific order, typically starting with the most complex molecule. Only after correctly assigning the coefficients, \( 5\mathrm{O}_{2} \) for oxygen in this case, can we claim the chemical equation is balanced and truly representative of the chemical process.

Combustion Reactions

A combustion reaction is an exothermic process where a fuel reacts with an oxidant, emitting heat, and sometimes light. The quintessential example of a fuel is propane, \( \mathrm{C}_{3}\mathrm{H}_{8} \), which reacts with oxygen to produce carbon dioxide and water. This kind of reaction is of immense practical value as it releases energy harnessed for heating, transportation, and in power plants.

Combustion is not only limited to burning in the open air but also includes controlled reactions such as those in vehicle engines and industrial furnaces. Significantly, efficient combustion requires adequate mixing of the fuel with the oxidant, often air, and must reach a sufficient temperature to ignite. Awareness of the conditions required for different combustion reactions is crucial for both safety and the optimization of energy production. For instance, in the case of propane, an ideal mix of fuel and air will ensure a 'clean' combustion, wherein the byproducts are just carbon dioxide and water, minimizing pollutants like carbon monoxide.

Chemical Stoichiometry

The concept of chemical stoichiometry deals with the quantitative relationships between reactants and products in a chemical reaction. It stems from the balanced chemical equation and enables us to understand the proportion of materials needed and produced. Stoichiometry is the bridge between the molecular world and the practical world, where we measure substances in grams, liters, or moles.

Take the balanced equation for the combustion of propane, for example: \( \mathrm{C}_{3}\mathrm{H}_{8} + 5\mathrm{O}_{2} \rightarrow 3\mathrm{CO}_{2} + 4\mathrm{H}_{2}\mathrm{O} \). Here, stoichiometry informs us that one mole of propane reacts with five moles of oxygen to produce three moles of carbon dioxide and four moles of water. This sets the stage for further calculations, such as determining the amount of oxygen needed to burn a specific quantity of propane or the volume of carbon dioxide produced in the process. Chemical stoichiometry is essential in industrial applications to ensure efficiency and cost-effectiveness and to minimize waste and environmental impact.