Formula mass is applicable in the case of ionic compounds.

Ionic compounds are formed by the transfer of electrons between a metal and a non-metal. In these compounds, the atoms are held together by strong electrostatic forces of attraction between positively charged metal ions and negatively charged non-metal ions. The overall charge of an ionic compound is neutral, meaning that the total positive charge from the metal ions is balanced by the total negative charge from the non-metal ions.

Ionic compounds have a definite chemical formula that represents the ratio of ions in the compound. This formula indicates the types and number of atoms present in the compound. The formula mass, also known as the molar mass or molecular weight, is calculated by summing up the atomic masses of all the atoms in the compound according to the ratio given in the chemical formula.

The formula mass is expressed in atomic mass units (amu) and is used to determine the amount of a substance in moles. It is an important concept in stoichiometry, which involves the quantitative relationships between reactants and products in chemical reactions. By knowing the formula mass of an ionic compound, we can determine the number of moles of the compound present in a given mass or vice versa using Avogadro's number and the molar mass.

In contrast, formula mass is not applicable to non-polar covalent compounds or non-polar organic compounds. Non-polar covalent compounds are formed by the sharing of electrons between two non-metal atoms. These compounds do not have charged ions, so the concept of formula mass, which is based on the ratio of ions, is not relevant. Instead, non-polar covalent compounds have a molecular mass, which represents the sum of the atomic masses of all the atoms in a molecule.

Similarly, non-polar organic compounds, which are covalent compounds composed of carbon and hydrogen atoms, also have a molecular mass rather than a formula mass. The molecular mass is calculated in the same way as the formula mass, by summing up the atomic masses of all the atoms in the molecule.

IONIC COMPOUND.