Question

Calculate the formula unit mass of ${\mathrm{CaCl}}_2$.

Answer 1

Definition of formula mass of an ionic compound

The sum of atomic masses of all the atoms in the ions of an ionic compound is known as the formula mass of an ionic compound.

Calculate the formula unit mass of ${\mathrm{CaCl}}_2$

${\mathrm{CaCl}}_2$ contains one calcium and two chloride ions.

We know that,

The atomic mass of calcium = $40\mathrm{u}$

The atomic mass of chlorine = $35.5$

Formula unit mass of ${\mathrm{CaCl}}_2$ = ($1\times$Atomic mass of calcium)$+$($2\times$Atomic mass of chlorine)

Formula unit mass of ${\mathrm{CaCl}}_2$ = $(1\times 40)+(2\times 35.5)\mathrm{u}$

Formula unit mass of ${\mathrm{CaCl}}_2$ = $111\mathrm{u}$.