Question

The formula unit mass of ${\text{MgCl}}_2$ is _____.

• A. 94.5 u
• B. 95 u
• C. 96.5 u
• D. 97 u

Answer 1

The correct option is B 95 u

Formula unit mass is used to calculate the mass of ionic compounds. It is the sum of the atomic masses of all the ions in the compound.

Hence, the formula unit mass of ${\text{MgCl}}_2$
= atomic mass of Mg + (2 $\times$ atomic mass of Cl) = 24 + (2 $\times$ 35.5) = 95 u.