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Weak Acids and Bases

Omkar Phatak
What are weak acids and bases? How are they classified? Read to know all about them.
Two of the most important chemical types, that you will study in your chemistry courses, are acids and bases. Testing the acidic or basic nature of a chemical is one of the first steps in their characterization, as it matters when you are choosing it for a specific application.

What are Weak Acids?
Most simply, an acid is any chemical that generates Hydrogen ions (H+), when dissolved in water. It is also defined as a proton (H+) donor. A more general definition is the following.
It is any chemical which accepts an electron pair, when it reacts with other substances. This last definition was provided by Lewis, and acids satisfying the condition are called Lewis acids.
They strongly react with metals and taste sour. A blue litmus paper will turn red, when it comes in contact with an acid. A chemical with a pH less than 7 is acidic.
The strength of an acid can be determined by how readily it dissociates in water, to release Hydrogen ions (H+), along with negative ions. Weak acids are defined as those which only partially dissociate in water. To put it simply, they do not completely ionize in water. In contrast, strong acids completely dissociate in water to release protons in the process.

Examples

Any chemical which has an ionizable proton could be a weak acid. Here are some of the most common ones found in nature.
  • Formic Acid (HCOOH)
  • Acetic Acid (CH3COOH)
  • Hydrofluoric Acid (HF)
  • Hydrogen Sulfide (H2S)
  • Hydrocyanic (HCN)

What are Weak Bases?
A base is any chemical which dissociates in water to release hydroxide ions (OH-). Bases are also defined as proton acceptors or donors of electron pairs. The electron pair donor definition is again attributed to Lewis and the ones that satisfy that condition are known as Lewis bases. Acids and bases are exactly complementary to each other.
When they come together, they neutralize each other, forming salts. A chemical with a pH greater than 7 is basic.
A weak base is any chemical, that weakly dissociates into water to produce hydroxide (OH-) ions. They are weakly ionizing bases in a water solution. These are the most common ones found in nature.

Examples

Here are the most common ones found in nature.
  • Ammonia (NH3)
  • Pyridine (C5H5N)
  • Trimethylamine (N (CH3)3)
  • Diethylamine (CH3CH2)2NH 
Weak acids and bases are more common than their strong counterparts, as they find many applications in our day-to-day life.