Question

A compound containing phosphorus and oxygen has a molar mass of 157.9 g/mol and an empirical formula of PO3 .

Answer 1

Answer: The molecular formula of the compound is $P_2O_6$

Explanation:

The molecular formula is the chemical formula that tells about the number of atoms of each element present in a compound. Molecular formula and empirical formula can also be the same when the number of atoms is in the simplest whole-number ratio.

To calculate the molecular formula, the number of atoms of the empirical formula is multiplied by a factor known as valency that is represented by the symbol, 'n'.

$n=\frac{\text{Molecular mass}}{\text{Empirical mass}}$        ...(1)

Given empirical formula is $PO_3$

Empirical mass = $[(1\times 30.97) + (3\times 15.99)]=78.94 g/mol$

Molecular mass = 157.9 g/mol

Plugging values in equation 1:

$n=\frac{157.9 g/mol}{78.94g/mol}\\\\n=2$

Molecular formula of the compound becomes $P_{2\times 1}O_{2\times 3}=P_2O_6$

Hence, the molecular formula of the compound is $P_2O_6$