Question

Calculate the molecular mass of: (a) Sodium Sulphate (b) Calcium Phosphate

Answer 1

Part (b)

1. Molar mass is the sum of the masses of all the individual atoms present in a molecule or compound.
2. The chemical formula of Sodium Sulphate is ${\mathrm{Na}}_2{\mathrm{SO}}_4$
3. The chemical formula of Calcium Phosphate ${\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2$
4. The atomic mass of Sodium Na is 23 u.
5. The atomic mass of Sulphur S is 32 u.
6. The atomic mass of Oxygen is 16 u.
7. The atomic mass of Phosphorous P is$$\begin{gathered} \mathrm{Molecular}\mathrm{mass}\mathrm{of}\mathrm{Calcium}\mathrm{Phosphate}{\mathrm{Ca}}_3{\left(\mathrm{PO}4\right)}_2=(\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{Calcium})\mathrm{x}3+(\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{Phosphorous})\mathrm{x}2 \\ +(\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{Oxygen})\mathrm{x}8 \end{gathered}$$

$=(40\mathrm{x}3)+(31\mathrm{x}2)+(16\mathrm{x}8)$

$=310\mathrm{g}/\mathrm{mole}$

The molecular mass of ${\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2$is 310 g/mole.