Question

What is the basicity of ${H_4}{P_2}{O_7}$ $?$

Answer 1

The basicity is the condition of an acid of being a base or the difficulty for an acid to react with a base determined by the number of hydrogen atoms that can be replaced in the acid. Simply the number of hydrogen atoms replaced by a base in a particular acid to get basicity of the given acid. Hence the basicity of the acids is equal to the hydrogen atom present in the acid.

Complete answer:
Basicity of a given acid is measured on a scale called the pH scale. The range pH scale goes from $0$ to $14$ . The pH value less than $7$ indicates acidity, whereas a pH value greater than $7$ indicates a basicity. When a pH value is $7$ indicates the given substance is neutral.
An ion is a positively or negatively charged atom (or group of atoms). Ions are classified into two types, namely cations and anions. Cations have more protons than electrons and so cations are positive charged ions. Whereas, anions have more electrons than protons and so anions are negative charged ions.
Given acid ${H_4}{P_2}{O_7}$ contains $4$ replaceable $H$ −atoms.
Hence, the basicity of ${H_4}{P_2}{O_7}$ is $4$ and it is a tetrabasic acid.

Note:
An ion is formed when an atom loses or gains electrons, so it contains an unequal number of electrons and protons. Also note that, anions are ions which gain one or more than one electron, whereas cations are ions which lose one or more than one electron.
A base is a substance that can accept hydrogen ions in water and can neutralize an acid.