Calculate the molecular mass of MgCO₃.

The molecular mass of the MgCO₃ can be calculated as:

Atomic mass of Magnesium = 24.3 a.m.u (a.m.u = atomic mass unit)

Atomic mass of Carbon = 12 a.m.u

Atomic mass of Oxygen = 16 a.m.u

We have one magnesium atom, one carbon atom, and three oxygen atom.

So, the total mass = 24.3 + 12 + (3 X 16)

= 84.3 a.m.u

The molecular mass of MgCO₃ is 84.3 a.m.u.