Find the formula unit mass of potassium chloride (KCl). Atomic mass — K = 39 u; Cl = 35.5 u.
74.5 u
Explanation
The formula unit mass of an ionic compound is the sum of the atomic masses of all the atoms present in a formula unit. For potassium chloride (KCl), the formula unit consists of one potassium atom and one chlorine atom. By multiplying the atomic mass of each element by the number of atoms of that element in the formula unit and adding them together, we arrive at the total formula unit mass.
Solution Steps
Identify atoms: Potassium chloride (KCl) contains 1 atom of Potassium (K) and 1 atom of Chlorine (Cl).
Note atomic masses: Atomic mass of K = 39 u, Atomic mass of Cl = 35.5 u.
Set up formula: Formula unit mass of KCl = (Atomic mass of K × 1) + (Atomic mass of Cl × 1)
Calculate: = (39 u × 1) + (35.5 u × 1) = 39 u + 35.5 u = 74.5 u