What is the formula unit mass of sodium chloride (NaCl)? (Atomic masses: Na = 23 u, Cl = 35.5 u)
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 58.5 u
The formula unit mass of an ionic compound is the sum of the atomic masses of all the atoms in its formula. One formula unit of NaCl has one sodium atom and one chlorine atom.
Mass of Na \(=23\,\mathrm{u}\)
Mass of Cl \(=35.5\,\mathrm{u}\)
Formula unit mass of NaCl \(=23+35.5=58.5\,\mathrm{u}\)