The term formula mass is a general term that can be applied to both ionic compounds and molecular compounds because

(a) ionic compounds exist as individual molecules
(b) molecular formulas are always empirical formulas
(c) not all formulas represent individual molecules
(d) molecular formulas are always Lewis formulas

is the answer letter a?

I don't think so; in fact, answer a is the reason some profs like to use formula mass instead of molar mass. That is, ionic compounds do NOT exist as individual molecules.

so it it letter c?

No, the correct answer is (c) not all formulas represent individual molecules. The term formula mass is a general term that can be applied to both ionic compounds and molecular compounds because not all formulas represent individual molecules. Ionic compounds exist as a lattice structure of alternating positive and negative ions, while molecular compounds exist as discrete molecules. Therefore, the concept of formula mass is used to calculate the total mass of the formula, regardless of whether it represents an ionic compound or a molecular compound.

No, the correct answer is option (c) - not all formulas represent individual molecules.

The term "formula mass" is used to refer to the sum of the atomic masses of all the atoms in a chemical formula. It can be applied to both ionic compounds and molecular compounds.

In the case of ionic compounds, the chemical formula represents the ratio of ions in the ionic lattice rather than individual molecules. For example, in sodium chloride (NaCl), the formula represents the ratio of one sodium ion to one chloride ion.

On the other hand, in molecular compounds, the chemical formula represents the actual number and types of atoms present in a molecule. For example, in water (H2O), the formula indicates that there are two hydrogen atoms bonded to one oxygen atom.

It is important to note that not all chemical formulas represent individual molecules. Some formulas may represent ionic compounds, which exist as a lattice of ions, or they may represent polyatomic ions, which are charged groups of atoms bonded together.

Therefore, the correct answer is option (c) - not all formulas represent individual molecules.