Studying science involves understanding the concepts that shape science.
Acid-base reactions can be described in several ways: by formula equations as reactions between substances, or by ionic equations as proton transfer reactions according to Bronsted’S model
The term ACID was first used in the seventeenth century; it comes from the Latin root ac-, meaning “sharp”, as in acetum, vinegar. Acids have long been recognized as a distinctive class of compounds whose aqueous solutions exhibit the following properties:
- A characteristic sour taste
- Ability to change the color of litmus from blue to red.
- React with certain metals to produce gaseous H2
- React with bases to form a salt and water.
- HNO3 + Ca(OH)2 àCa(NO3)2 + H2O
- NaOH + H2SO4 àNa2SO4 + H2O
The first chemical definition of an acid turned out to be wrong: in 1787, Antoine Lavoisier, as part of his masterful classification of substances, identified the known acids as a separate group of the “complex substances” (compounds). Their special nature, he postulated, derived from the presence of some common element that embodies the “acidity” principle, which he named oxygen, derived from the Greek for “acid former”. Lavoisier had assigned this name to the new gaseous element that Joseph Priestly had discovered a few years earlier as the essential substance that supports combustion. Many combustion products (oxides) do give acidic solutions, and oxygen is in fact present in most acids, so Lavoisier’s mistake is understandable.
The name BASE has long been associated with a class of compounds whose aqueous solutions are characterized by:
- A bitter taste
- A“soapy” feeling when applied to the skin;
- Ability to restore the original blue color of litmus that has been turned red by acids
- Ability to react with acids to form salts. The word “alkali” is synonymous with base. It is of Arabic origin, but the root word comes from the same Latin kalium (potash) that is the origin of the symbol for potassium; wood ashes have been the traditional source of the strong base KOH since ancient times.