Question

What is the formula mass of ${\mathrm{CuSO}}_4$?

Answer 1

Step 1: Formula mass:

• “The formula mass of a substance is defined as the sum of the atomic masses of constituent atoms in an ionic compound.”

Step 2: Atomic mass of each atom in ${\mathbf{CuSO}}_{\mathbf{4}}$:

Copper sulfate (${\mathrm{CuSO}}_4$) has one Copper$\mathrm{\left(}\mathrm{Cu}\mathrm{\right)}$ atom, one Sulphur$\left(\mathrm{S}\right)$ atom, and four Oxygen$\left(\mathrm{O}\right)$ atoms.

$$\begin{gathered} \text{Atomic mass of one Copper atom= 63.5 amu} \\ \text{Atomic mass of one Sulpur atom= 32 amu} \\ \text{Atomic mass of one Oxygen atom= 16 amu} \\ \text{Atomic mass of four Oxygen atoms = 4×16 amu =64 amu} \end{gathered}$$

Step 3: Formula mass of ${\mathbf{CuSO}}_{\mathbf{4}}$:

$\text{Formula mass = (63.5 + 32 + 64) amu =159.5 amu}$

Thus, the formula mass of ${\mathrm{CuSO}}_4$ is $159.5\mathrm{amu}$.