Base
Definition and meaning of Base in chemistry.
In chemistry, a base is a substance that can neutralize an acid. It donates hydroxide ions (OH⁻) in water or accepts protons (H⁺) from other molecules. Bases typically produce aqueous solutions with a pH greater than 7 at 25 °C.
In more detail
Chemists use two main theories to define how bases behave in chemical reactions. The Arrhenius theory states that a base releases hydroxide ions when dissolved in water. The broader Brønsted-Lowry theory defines a base as any molecule that accepts a proton.
A proton in this context is simply a hydrogen ion with a positive charge. Bases can be classified as either strong or weak depending on their chemical behavior. A strong base completely ionizes in water to release all its available hydroxide ions.
Sodium hydroxide is a common strong base used in drain cleaners and soap making. A weak base only partially ionizes and establishes a dynamic chemical equilibrium in solution. Ammonia is a well-known weak base used frequently in fertilizers and household glass cleaners.
Bases feel distinctly slippery to the touch because they react with oils on human skin. They turn red litmus paper blue and taste bitter, though you must never taste lab chemicals. In biological systems, specific bases help maintain the proper pH levels in human blood.
They are also essential in water treatment plants and large-scale industrial chemical synthesis. A common student misconception is that bases are inherently less dangerous than strong acids. In reality, concentrated strong bases can cause severe, immediate chemical burns to organic tissue.
Key facts
| Field | General Chemistry |
|---|---|
| pH Range | Greater than 7 at 25 °C |
| Brønsted-Lowry definition | Proton (H⁺) acceptor |
| Arrhenius definition | Hydroxide (OH⁻) donor |
| Common strong bases | NaOH, KOH, Ca(OH)2 |
| Common weak base | Ammonia (NH3) |
Ammonia (NH3) acts as a classic Brønsted-Lowry weak base in liquid water. It accepts a single proton from a water molecule during a reversible reaction. The chemical equation is NH3(aq) + H2O(l) ⇌ NH4⁺(aq) + OH⁻(aq). This process generates the hydroxide ions that give the solution its basic properties.
Frequently asked questions
What is the difference between a strong and weak base?
A strong base completely ionizes in water to release all its hydroxide ions. A weak base only partially ionizes and establishes an equilibrium between ionized and molecular forms.
How do bases interact with acids?
Bases and acids undergo neutralization reactions that typically produce liquid water and a salt. For example, mixing sodium hydroxide and hydrochloric acid creates ordinary table salt and water.
Why do basic solutions feel slippery on your skin?
Bases react with the natural oils and fatty acids found on your skin. This chemical reaction creates a small amount of soap, which causes the slippery sensation.