Strong Bases: Properties, Applications and Examples

Laboratory technician using a pipette to fill a solution in a test tube, close-up. — Chemists need to know how acids, bases and aqueous solutions all interact. Guido Mieth / Getty Images

In chemistry, the classification of substances into acids and bases is fundamental.

Within this spectrum, strong bases, such as sodium hydroxide and calcium hydroxide, are potent agents capable of driving critical chemical reactions and facilitating various industrial processes. This makes them useful in both academic research and practical applications.

Let's take a closer look at the properties, behaviors and applications of strong bases to better understand their significance.

What Are Strong Bases?

In the world of chemistry, bases are substances that can accept protons (H⁺ ions) or donate pairs of electrons. When you dissolve bases in water, they increase the concentration of hydroxide ions (OH^-).

A strong base, unlike a weak base, dissociates (separates) completely into ions when it dissolves in water. This property makes it a highly efficient proton acceptor and catalyst for chemical reactions.

What Are Proton Acceptors?

Proton acceptors are molecules with the ability to accept a proton (H⁺) from another substance during a chemical reaction. Proton acceptors are bases, which can be either strong or weak.

In the context of acid-base reactions, when a proton acceptor accepts a proton from an acid, it forms a new compound called a conjugate acid.

In aqueous solutions, proton acceptors often involve species with lone pairs of electrons, such as hydroxide ions (OH^-) in a strong base or ammonia (NH₃) in a weak base.

These lone pairs of electrons are attracted to the positively charged hydrogen ion (proton), allowing the proton to bond with the proton acceptors and form new compounds.

Proton Acceptor Example

Take, for example, the reaction between ammonia (NH₃) and water (H₂O):

NH₃ + H₂O → NH₄+ + OH^-

In this reaction, ammonia acts as a proton acceptor, accepting a proton (H⁺) from water to form the ammonium ion (NH₄⁺) and hydroxide ion (OH^-). Thus, ammonia is acting as a base by accepting a proton.

Chemical Properties of Strong Bases

Strong bases exhibit several key chemical properties due to their ability to completely dissociate into hydroxide ions (OH^-) and cations in an aqueous solution. Some of the notable chemical properties of strong bases include:

Conductivity: Aqueous solutions of strong bases are good conductors of electricity due to the presence of ions. The high concentration of ions allows for the flow of electric current.
Corrosive: Strong bases are often corrosive to organic materials, metals and tissues. They can cause severe chemical burns upon contact with your skin. Protective gear, such as gloves, goggles and lab coats, is essential to mitigate these risks.
High pH: Strong bases cause aqueous solutions to have a high pH, typically greater than 7 on the pH scale. This is due to the high concentration of hydroxide ions produced when the base dissociates completely.
Ionization: Strong bases ionize completely in aqueous solutions, meaning that nearly all of the molecules of the base dissociate into ions. This results in a high concentration of hydroxide ions in the solution.
Neutralization: Strong bases react readily with strong acids to form water and a salt. This process is known as neutralization. For example, when sodium hydroxide (NaOH) reacts with hydrochloric acid (HCl), it forms water (H₂O) and sodium chloride (NaCl).
Solubility: Many strong bases are highly soluble in water, facilitating their use in various applications such as chemical synthesis, cleaning agents and pH regulation.

8 Examples of Strong Bases

Several compounds exemplify the strength of bases. Prominently among them are hydroxides of alkali and alkaline earth metals. Here are eight strong bases to familiarize yourself with:

Calcium hydroxide: Ca(OH)₂
Lithium hydroxide: LiOH
Sodium hydroxide: NaOH
Potassium hydroxide: KOH
Barium hydroxide: Ba(OH)₂
Strontium hydroxide: Sr(OH)₂
Rubidium hydroxide: RbOH
Cesium hydroxide: CsOH

These compounds, when they dissolve in water, liberate hydroxide ions readily, showcasing their strong basic nature.

Applications of Strong Bases

Strong bases find extensive utility across various fields. In industries, they are crucial in the production of soaps, detergents and various chemicals.

Sodium hydroxide, commonly known as caustic soda, is indispensable in the manufacture of paper, textiles and cleaning agents. Potassium hydroxide is essential in the production of fertilizers and batteries.

Additionally, strong bases play a vital role in wastewater treatment, neutralizing acidic sewage to prevent environmental damage.

Strong Bases vs. Strong Acids

To better understand strong bases, it helps to contrast them with strong acids. These two categories of compounds have distinct properties and behaviors in aqueous solutions.

Strong bases, such as sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)₂) and barium hydroxide (Ba(OH)₂), are typically hydroxides of alkali metals and alkaline earth metals. They are known for their ability to completely dissociate into hydroxide ions (OH^-) and cations in aqueous solutions.

For instance, when calcium hydroxide (Ca(OH)₂) dissolves in water, it ionizes completely to produce calcium ions (Ca₂⁺) and hydroxide ions (OH^-). Strong bases are capable of neutralizing strong acids and turning litmus paper blue.

On the other hand, strong acids, such as hydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃), hydrobromic acid (HBr) and hydroiodic acid (HI), are acids that completely dissociate into hydrogen ions (H⁺) and anions in aqueous solutions.

For example, when hydrochloric acid (HCl) dissolves in water, it ionizes completely to form hydrogen ions (H⁺) and chloride ions (Cl^-). Strong acids have a very low pH and, like strong bases, are capable of causing severe chemical burns. They are also strong proton donors.

Weak Bases vs. Weak Acids

Weak bases, such as ammonia (NH₃) and organic amines, are compounds that partially dissociate in aqueous solutions to release hydroxide ions (OH^-) and cations. They are characterized by being electron pair donors and proton acceptors.

Weak acids also only partially dissociate in aqueous solutions. Examples include carbonic acid (H₂CO₃), acetic acid (CH₃COOH) and citric acid (C₆H₈O₇). They have higher pH values compared to strong acids and do not completely ionize.

4 Other Types of Bases

In addition to strong bases and weak bases, there are other ways of categorizing chemical bases. Here are some different categories worth knowing.

Arrhenius bases: These are substances that produce hydroxide ions (OH^-) when they dissolve in water. Examples include sodium hydroxide (NaOH), potassium hydroxide (KOH) and calcium hydroxide (Ca(OH)₂).
Brønsted-Lowry bases: According to the Brønsted-Lowry theory, bases are substances that can accept protons (H⁺ ions). This theory extends the concept of bases beyond hydroxide ions. An example of a Brønsted-Lowry base is ammonia (NH₃).
Conjugate bases: This is the species that remains after an acid donates a proton in a reaction. A conjugate base forms when an acid loses a hydrogen ion (H⁺). For example, in the reaction between hydrochloric acid (HCl) and water (H₂O), chloride ion (Cl^-) is the conjugate base of hydrochloric acid (HCl).
Lewis bases: These substances can donate electron pairs to form coordinate covalent bonds. This definition of bases is broader than both Arrhenius and Brønsted-Lowry definitions. Lewis bases include molecules with lone pairs of electrons, as well as molecules with pi bonds or other electron-rich regions.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.