Question

Calculate the molecular mass of (a) Sodium Sulphate

Answer 1

Part (a)

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 atomic mass of Sodium Na is 23 u.
4. The atomic mass of Sulphur S is 32 u.
5. The atomic mass of Oxygen is 16 u.

$\mathrm{Molecular}\mathrm{mass}\mathrm{of}\mathrm{Sodium}\mathrm{Sulphate}{\mathrm{Na}}_2{\mathrm{SO}}_4=(\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{Sodium})\mathrm{x}2+(\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{Sulphur})\mathrm{x}1+(\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{Oxygen})\mathrm{x}4$ $=(23\mathrm{x}2)+(32\mathrm{x}1)+(16\mathrm{x}4)$

$=142\mathrm{g}/\mathrm{mole}$

The molecular mass of sodium sulphate ${\mathrm{Na}}_2{\mathrm{SO}}_4$is 142 g/mole.