Question

What is the basicity of orthophosphoric acid?
a.) One
b.) Two
c.) Three
d.) Four

Answer 1

Hint: To solve this question first of all we will see what is orthophosphorous acid and what is basicity of an acid, how we calculate then we will be able to tell the basicity of this question easily. As we know the basicity is the number of replaceable hydrogen atoms or acidic hydrogen that an acid has in its molecule. For finding the basicity we need to draw the structure of the orthophosphoric acid.

Complete step by step solution: Acidic hydrogen- the necessary condition for a hydrogen atom to be acidic is that it must be connected to the electronegative atoms like oxygen or fluorine. In the case of orthophosphoric acid, we will see a number of hydrogen atoms connected to the oxygen for calculating its basicity.
\[\begin{array}{*{20}{c}}
  {}&{\begin{array}{*{20}{c}}
  O \\
  {||}
\end{array}}&{} \\
  {H - O - }&{P - }&{O - H} \\
  {}&{\begin{array}{*{20}{c}}
  | \\
  H
\end{array}}&{}
\end{array}\]
The above compound is the orthophosphorous acid
The number of H atoms bonded to the oxygen atoms in the above compound is equal to 2.
Therefore, the basicity of the orthophosphorous acid is 2.

Hence the correct option is B.

Note: The orthophosphorous acid is also known as phosphorous acid. It is used as a reducing agent in the chemical analysis because they are easily oxidized to phosphoric acid and phosphate salts. It is a colourless and crystalline substance. It is one of the oxyacids of the phosphorus and the other oxyacids of the phosphorus are phosphoric acid and the basicity of this acid is 3 because it contains 3 acidic hydrogen atoms. The chemical formula for orthophosphoric acid is ${H_3}P{O_4}$