In chemistry, a base is a substance that can accept protons or donate electron pairs. When dissolved in water, bases increase the concentration of hydroxide ions. Understanding the characteristics of strong bases is important for their safe handling and appropriate use.
Defining a Strong Base
A strong base is characterized by its ability to completely dissociate into ions when dissolved in water. For bases, this process primarily involves the release of hydroxide ions (OH-). The higher the concentration of these free hydroxide ions in a solution, the stronger the basicity of that solution. This fundamental chemical property differentiates strong bases from weak bases, which only partially dissociate in water.
Observable Properties and Tests
Strong bases can be identified by several key properties and tests. One primary indicator is pH measurement. Strong bases produce solutions with a very high pH, typically ranging from 13 to 14. This can be determined using pH paper, which changes color when dipped into the solution, or with a pH meter, which provides a more precise numerical reading.
pH indicators also help identify strong bases. For instance, phenolphthalein is a common indicator that remains colorless in acidic or neutral solutions but turns bright pink in the presence of a strong base, typically above pH 10. Litmus paper, another widely used indicator, changes from red to blue when exposed to a basic solution.
Strong bases also exhibit excellent electrical conductivity when dissolved in water. This property stems directly from their complete dissociation into ions. When a strong base dissolves, it releases a high concentration of mobile ions, such as metal cations and hydroxide anions, which can readily carry an electrical charge through the solution. If a circuit is completed through a strong base solution, a light bulb connected to it would glow brightly, indicating the presence of many charge carriers. This contrasts with weak bases, which produce fewer ions and thus conduct electricity less effectively.
Common Examples of Strong Bases
Several common substances are recognized as strong bases, primarily including the hydroxides of alkali metals and some alkaline earth metals. Sodium hydroxide (NaOH), commonly known as lye or caustic soda, is a widely used strong base found in drain cleaners and soap manufacturing. Potassium hydroxide (KOH), or caustic potash, is another strong alkali metal hydroxide used in liquid soaps and some industrial processes. Lithium hydroxide (LiOH) is also a strong base, often used in carbon dioxide absorption systems, such as those in spacecraft.
Alkaline earth metal hydroxides are also strong bases, though their solubility varies. Calcium hydroxide (Ca(OH)2), known as limewater or slaked lime, is used in agriculture to neutralize acidic soils and in water treatment. Barium hydroxide (Ba(OH)2) is another example, utilized in various chemical syntheses. Strontium hydroxide (Sr(OH)2) is similarly a strong base, finding applications in refining sugar.
Safety When Handling Strong Bases
Handling strong bases requires careful attention to safety due to their corrosive nature. These substances can cause severe burns to skin and eyes upon contact, sometimes without immediate pain, leading to extensive tissue damage. It is important to always wear personal protective equipment (PPE), including chemical-resistant gloves, splash goggles, and a lab coat, to prevent direct exposure. A face shield should be used when handling larger quantities or when there is a potential for splashing.
Proper ventilation is important when working with strong bases, as some may produce irritating or hazardous fumes. When preparing solutions, always add the base slowly to water, rather than adding water to the base. This procedure helps to control the significant heat generated during the dissolution process, which can otherwise cause violent boiling and splashing. In case of accidental skin or eye contact, immediately rinse the affected area with plenty of water for at least 15 minutes and seek medical attention.