Question

The empirical formula of a compound is found to be P2O5. Experiments show that the molar mass of the compound is 560g/mol. What is the molecular formula of the compound?

Answer 1

The molar mass of P2O5 is 141.94 g/mol.

Divide the given mass by the molar mass of the compound.

$\frac{560\cdot\frac{g}{\text{mol}}}{141.94\cdot\frac{g}{\text{mol}}}\approx4$

This means we need to multiply each subscript by 4 to find the molecular formula.

Therefore, the molecular formula is

$P_8O_{10}$