Question

Calculate the molecular weight of the following

Aluminium hydroxide ($\mathrm{Al}{\left(\mathrm{OH}\right)}_3$)

Answer 1

Definition of molecular weight

Molecular weight, also called molecular mass, is the mass of a molecule of a substance, based on 12 as the atomic weight of carbon-12. It is calculated in practice by summing the atomic weights of the atoms making up the substance's molecular formula.

Calculation

Atomic mass of $\mathrm{Al}=27,\mathrm{O}=16,\mathrm{H}=1$

The molecular weight = $=27+3(16+1)=78\mathrm{amu}$

Therefore, the molecular weight of Aluminium hydroxide $\mathrm{Al}{\left(\mathrm{OH}\right)}_3=78\mathrm{amu}$=78amu