Question

What is the molecular weight of $S{O}_4$ ?

Answer 1

Hint: We have to remember that the molecular weight is defined as the sum of all atoms in the molecule. When two or more atoms combine they form a molecule. Each atom has a specific mass and by using that we can calculate the total molecular weight of the molecule. Mass of sulphur is $32.07g/mol$ and that of oxygen is $16g/mol$ here mole represents mole which is the SI unit for the amount of substance.

Complete answer:
As we know in the molecule we have sulphur atom and oxygen atom. The subscript of oxygen that is $4$ indicates there are four atoms of oxygen.
Hence by using the mass given the molecular weight is calculated.
Since in the molecule given two kinds of atoms are present one of sulphur and one oxygen.
The formula can written as:
$\text{Molecular weight}=\text{Mass of atom}\times \text{Number of atom}$
In $S{O}_4$,
Atom 1 = Sulphur $$ Number of atom 1 = one atom
Atom 2=Oxygen $$ Number of atom 2 = four atoms
Molecular weight = (mass of sulphur × $1$) +( mass of oxygen ×$4$)
Molecular weight $=\left(32.07\times 1\right)+\left(16\times 4\right)$
Molecular weight $=32.07+64$
Molecular weight $=96.07g/mol$
The molecular weight of $S{O}_4$ is calculated as $96.07g/mol$

Note:
As we know that the molecular mass is similar to molecular weight. It is calculated the same way as the molecular weight is calculated, the only difference lies in the unit for molecular mass it is amu which is called atomic mass unit. Whereas Formula mass is another mass which is calculated for species which have positive and negative entities, it also calculated the same way.