In chemistry, a base is any substance which receives protons. Sometimes called alkalies, bases are defined as many things although there are three major definitions, Arrhenius, Lewis, and Brönsted-Lowry bases. Any substance with a pH level higher than 7 is basic, being opposite of acids on the pH scale. They react with acids, making them neutral and forming water and salts. There are a wide variety of uses for basic substances, the most common of which is cleaning.
The most defining property of bases is their ability to readily accept protons from other substances. Another major property of bases is their reaction with acids. When an acid and a base are mixed the base reacts with the acid and neutralizes it, forming salts and water. Basic substances react with grease and oil, dissolving them. A slippery sensation is felt when basic solutions are touched which is partly attributed to the ions. When tasted, bases are very bitter and give certain foods their bitter taste where they are present. When red litmus is exposed to a basic solution, it changes from a red hue to a blue one. The strength of bases varies depending on how readily it receives protons. Strong bases are often caustic, or corrosive. When caustic substances come into contact with the skin they cause severe chemical burns.
The three definitions of bases are Arrhenius bases, Brönsted-Lowry bases, and Lewis bases.
An Arrhenius base is one that gives up hydroxide ions into aqueous solutions. This definition was put forth by the Swedish chemist Svante Arrhenius in the 1880's. This definition is outdated because it only concerns bases in aqueous solutions and does not take into consideration basic compounds that do not have an OH group. As a result this is the most narrow of the three definitions of bases(Cox p389-390).
A Brönsted-Lowry base is defined as a substance which receives protons. This definition was created by a Danish chemist by the name of J. N. Brönsted and a British chemist named I. M. Lowry in 1923. Brönsted-Lowry bases are paired with acids, forming what is referred to as conjugate pairs. When a Brönsted-Lowry acid goes through deprotonation (the process of losing a proton) it forms something that will readily receive a proton, forming the conjugate base. The same is true when the process is reversed and a Brönsted-Lowry base becomes the conjugate acid. All bases that fall under the definition of an Arrhenius base are also a Brönsted-Lowry base and, because the Brönsted-Lowry definition is more broad, it includes bases that do not fall under the Arrhenius definition(Cox, Porch, Wetzel, p391). This is the most commonly used definition of bases.(Cox p392)
Brönsted and Lowry were not the only chemists proposing new ideas about bases in 1923, an American chemist named Gilbert N. Lewis proposed his own definition in the same year. The Lewis definition is the most broad of the three and includes Arrhenius bases, Brönsted-Lowry bases, and more. A Lewis base is one that that is able to give a pair of electrons. The definition is based off of the fact that bases have at least one unbonded pair of electrons and acids have at least one unoccupied orbital. Lewis bases that are combined with lewis acids form covalent bonds between the two substances.(Cox p392)
- Main Article: pH
The pH scale measures how acidic or basic a substance is. It was created by Danish chemist Soren P. L. Sorenson in 1909. The pH scale was created to describe the concentrations of hydronium and hydroxide ions in acids and bases in a quick and easy way(Cox, Porch, Wetzel p396). The scale goes from 0 to 14; the middle of the scale, 7, is neutral. Any substance that has a pH above 7 is basic and any substance below 7 is acidic. Weak bases are those that are closer to pH 7 while strong bases are closer to pH 14. The formula for pH is -log [H3O+]. The higher the concentration of hydronium ions, the higher the pH.
There are a wide array of uses for bases in our world. Most of them are industrial but bases can be found in the home and they are even used by the human body.
Bases are widely used for industrial purposes in America. A very common basic compound is Sodium Hydroxide or caustic soda. Its chemical formula is NaOH and it is most commonly used to neutralize acids but is also used in the manufacture of multiple products such as soaps, rayon, and paper. In the rayon manufacturing process the reaction that occurs between between sodium hydroxide and cellulose is the key process. It is also used in the petroleum refining process to neutralize or remove acids. Sodium hydroxide can also be utilized for its sodium ions in reactions that create other sodium compounds.
Bases are used in cleaning solutions such as soap because they can dissolve grease. Sodium hydroxide is also used in several domestic cleaning products such as drain and oven cleaners. When a clog forms in a drain pipe it is usually comprised of fats and grease so it makes sense to use a compound such as sodium hydroxide because it converts these fats to soap which will then dissolve in water. This process also occurs with the oven cleaner because it converts the fats in the oven to soap which can then be easily wiped away. Another commonly used basic substance is Ammonia, which is found in fertilizers and cleaners.
Basic substances are found all throughout nature. Human blood is a weak base ranging from pH 7.35 to 7.45 depending on how much CO2 is in the blood.(Wile, Shannon p318,436) There are many basic compounds in the body which act to neutralize acids, one of these is bicarbonate (HCO3). It is a weak base and found in extracellular fluids. Its function is to neutralize any acids that find their way into the extracellular fluids. Another weak base within the human body is hydrogen phosphate (HPO42-). Hydrogen phosphate can be located in cells and nephron tubules.(Wile p473-474)
- Bases ScienceByJones.com, Larry Jones, March 2, 2007.
- Chemistry for Christian Schools, Heather E. Cox, Thomas E. Porch, D.M.D., John S Wetzel, M.S,. Bob Jones University Press.
- pH Scale Virtual Chembook. Elmhurst College. Charles E. Ophardt. 2003.'
- Sodium Hydroxide - Sodium hydroxide in household products, Industrial uses of sodium hydroxide Science Encyclopedia, jrank.org
- The Human Body: Fearfully and Wonderfully Made! by Dr. Jay L. Wile, and Marilyn M. Shannon, M.A., Apologia Educational Ministries, Inc., 2001.
- Ammonia Multiple Authors, Wikipedia.org.