Question

The major use of alkanes has been in _____ reactions, as a source of heat and light.

Short answer

The major use of alkanes has been in combustion reactions, as a source of heat and light.

Step-by-step solution

Identify the properties and reactions of alkanes

Alkanes are hydrocarbons that have only single covalent bonds between carbon atoms (C-C) and between carbon and hydrogen atoms (C-H). They are generally unreactive and nonpolar, making them poor solvents for polar substances. The most common reactions that alkanes undergo are combustion reactions, where they react with oxygen to form carbon dioxide and water.

Fill in the blank with the appropriate reaction type

As alkanes undergo combustion reactions with oxygen to generate heat and light, the correct answer is that the major use of alkanes has been in combustion reactions. So, the complete sentence would be: The major use of alkanes has been in combustion reactions, as a source of heat and light.

Key concepts

Properties of Alkanes

Alkanes, often referred to as paraffins, are hydrocarbons that constitute the simplest class of organic compounds. Their distinguishing feature is the presence of only single covalent bonds within their molecular structure. This specific bonding leads to a unique set of properties that include being generally non-reactive, which is why they are not easily broken down by acids or bases.

They are also nonpolar molecules and, as such, do not mix well with polar solvents like water — this property is crucial when considering their applications. For instance, the nonpolarity of alkanes makes them useful as lubricants or as part of the hydrophobic cores in cell membranes. Most importantly, alkanes are excellent energy sources due to their high carbon and hydrogen content, making them pivotal in combustion reactions to produce heat and light. This combustion involves a chemical reaction with oxygen that results in the formation of carbon dioxide, water vapor, and energy release.

Hydrocarbons

Hydrocarbons are organic compounds composed entirely of hydrogen and carbon atoms. They are the foundation of organic chemistry and serve as the building blocks for more complex molecules. Alkanes form a major subset of hydrocarbons where each carbon atom is saturated with hydrogen atoms to produce a stable, tetrahedral carbon framework.

Hydrocarbons are divided into various categories based on their structure — alkanes, alkenes, alkynes, and aromatic hydrocarbons. These categories differ based on the types of bonds between carbon atoms; alkanes have single bonds, alkenes have double bonds, alkynes have triple bonds, and aromatic hydrocarbons have a ring with alternate single and double bonds. Hydrocarbons play a significant role in modern society, primarily as fuels like gasoline, diesel, and natural gas, due to their combustibility and energy-rich nature.

Covalent Bonds

Covalent bonds are a type of chemical bond where pairs of electrons are shared between atoms. This kind of bonding is found in nonmetallic elements and compounds, including organic molecules like alkanes. In a covalent bond, the shared electrons allow each atom to achieve a stable electronic configuration, usually resembling that of a noble gas.

The strength of covalent bonds plays a key role in determining the stability and properties of a molecule. In alkanes, each carbon atom forms four covalent bonds with either other carbon atoms or hydrogen atoms, resulting in a saturated hydrocarbon chain. These bonds give alkanes their stable, non-reactive nature, which is why they do not easily participate in chemical reactions unless conditions are extreme, like high temperatures in combustion processes, where they can be oxidized to release energy.