Question

Formula unit mass is used for:
A. Molecules
B. Ionic compounds
C. Uncharged compounds
D. All of the above

Answer 1

Hint: In a chemical formula, we use the elemental symbols from the periodic table to indicate which elements are present, and we use subscripts to indicate how many atoms of each element exist within the molecule. Now figure out what could be a formula unit mass.

Complete step by step answer:

Molecules: A molecule is defined as two or more atoms of the same element that are bound together. A molecule may be homonuclear, which means, it consists of atoms of one chemical element, as with oxygen $({ O }_{ 2 })$; or it may be heteronuclear, a chemical compound composed of more than one element, as with water $({ H }_{ 2 }O)$.
Ionic compounds: An ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. The compound is neutral overall, but consists of positively charged ions called cations and negatively charged ions called anions.
Uncharged compounds: The sum of the oxidation numbers in an uncharged compound is zero.
Formula unit mass: We need the ability to determine the mass of the formula of an ionic compound. This quantity is called the formula mass. The formula mass is obtained by adding the masses of each individual atom in the formula of the compound. Because a proper formula is electrically neutral (with no net electrons gained or lost), the ions can be considered atoms for the purpose of calculating the formula mass.

Hence, concluding all these statements we can finally get the correct answer for the above question is B.

Note: Calculating the formula mass of sodium chloride (NaCl):
This formula mass is the sum of the atomic masses of one sodium atom and one chlorine atom, which we find from the periodic table; here, we use the masses to two decimal places:
Na: 22.99 amu
Cl: +35.34 amu
Total: 58.44 amu
To two decimal places, the formula mass of NaCl is 58.44 amu.