Which information must be known about a compound to find the molecular formula from the empirical formula?
density
formula mass
percent composition
mole ratio
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percent composition

Explanation:

Molecular formula is the chemical formula which depicts the actual number of atoms of each element present in the compound.  

Empirical formula is the simplest chemical formula which depicts the whole number of atoms of each element present in the compound.

To calculate the molecular formula we need to know the molecular weight which can be calculated when percent composition is known.

The molecular formula will be=

Thus percent composition must be known about a compound to find the molecular formula from the empirical formula.