Final answer:
To find the molecular formula of a compound whose empirical formula is P2O5 and molar mass is 283.89 g/mol, calculate the molar mass of the empirical formula and divide the molar mass of the compound by this to find the ratio. The molecular formula is found to be P4O10, which is twice the empirical formula.
Step-by-step explanation:
The empirical formula provided is P2O5, which indicates the most basic ratio of phosphorus to oxygen in the compound. To find the molecular formula, you first need to calculate the molar mass of the empirical formula (empirical molar mass). The atomic masses of phosphorus and oxygen are approximately 30.97 g/mol and 16.00 g/mol, respectively. Thus, the molar mass of P2O5 is (2 × 30.97) + (5 × 16.00) = 141.94 g/mol.
Next, you divide the experimental molar mass of the compound by the empirical molar mass to find the ratio of the molecular formula to the empirical formula: 283.89 g/mol ÷ 141.94 g/mol ≈ 2. Therefore, the molecular formula is twice that of the empirical formula.
Multiplied by the ratio, the molecular formula for the compound is P4O10.