Question

Calculate the formula unit mass of CaCl2.

Answer 1

The formula unit mass is the sum of the atomic masses of all the atoms present in the formula of the compound multiplied by the number of atoms involved in the compound.

To calculate the formula unit mass of a CaCl₂ (Calcium chloride), we should know the following things.

1. Atomic mass calcium (Ca) = 40 u
2. Atomic mass of chlorine (Cl) = 35.5 u
3. Number of atoms of calcium (Ca) = 1
4. Number of atoms of chlorine (Cl) = 2

Calculations.

$$\begin{gathered} \mathrm{Formula}\mathrm{unit}\mathrm{mass}=(\mathrm{atomic}\mathrm{mass}\mathrm{of}\mathrm{calcium}\mathrm{x}1)+(\mathrm{atomic}\mathrm{mass}\mathrm{of}\mathrm{chlorine}\mathrm{x}2) \\ =(40\mathrm{x}1)+(35.5\mathrm{x}2) \\ =111\mathrm{amu} \end{gathered}$$

Thus, the formula unit mass of CaCl₂ is 111 amu.