Which of the following statements correctly describes the formula weight (molar mass) of a compound?

• A. It is the number of molecules present in one mole of the compound.
• B. It is the sum of the atomic masses of all atoms present in one formula unit of the compound, expressed in grams per mole.
• C. It is the mass of one atom of the compound, expressed in grams.
• D. It is the ratio of the number of atoms to the number of molecules in a sample.

Answer: (B)

Verified step by step guidance

1. Understand that the formula weight (or molar mass) of a compound refers to the mass of one mole of that compound, which is related to the sum of the atomic masses of all atoms in its formula unit.
2. Recall that the atomic mass of each element is given in atomic mass units (amu) and can be found on the periodic table; the formula weight is calculated by adding these atomic masses together according to the number of each type of atom in the compound.
3. Recognize that the formula weight is expressed in grams per mole (g/mol), which means it represents the mass of one mole (6.022 \times 10^{23} entities) of the compound.
4. Note that the formula weight is not the number of molecules, nor the mass of a single atom, nor a ratio of atoms to molecules; it specifically quantifies the mass of one mole of the compound based on its atomic composition.
5. Therefore, the correct description is: the formula weight (molar mass) is the sum of the atomic masses of all atoms present in one formula unit of the compound, expressed in grams per mole.