Question

What are the five characteristics of a base?

Answer 1

Hint :A base is a substance which has a characteristic bitter taste, is slippery to touch, changes the colour of litmus from red to blue, has a pH greater than $7$ and reacts with acids to undergo neutralization reaction. Bases also promote certain chemical reactions, known as base catalysis.


Complete Step By Step Answer:
In Chemistry, a base is simply put as a substance that reacts with an acid in an acid-base reaction. A base is also defined and described using theories like the Bronsted-Lowry theory, the Arrhenius theory, Lewis theory of acids and bases and the Lux-Flood concept. It is important to understand that we cannot say one theory is right or wrong; we merely use the theory that is convenient owing to the situation.
According to Arrhenius theory, a base is a hydroxyl compound which releases $O{H^ - }$ions in aqueous solution, whereas in Bronsted-Lowry theory, it is said that a base is a substance which has the tendency to accept a proton from any other substance. In Lewis theory, a base is a substance which can donate a pair of electrons. In accordance with the Lux-Flood concept, a base is a species which donates an oxide ion or other negative ions.
A base exhibits five major characteristics which include:
- Bases have characteristic bitter taste
- Bases are soapy to touch
- Bases change the colour of litmus from red to blue
- Bases have pH greater than $7$
- Bases react with acids to form salts
Some examples of bases are: $KOH,\,NaOH,\,Ba{(OH)_2}$ et cetera.

Note :
Acids show characteristics opposite to that of base: they taste sour, they change the colour of litmus from blue to red, they have pH less than $7$ , and they react with some metals. Although such differences are seen in their characters, one common feature between acids and bases is that on reacting with each other they undergo neutralization reaction, giving corresponding salt and a molecule of water as the product.