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

Answer : The correct option is, (B) formula mass

Explanation :

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

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

For determining the molecular formula, we need to determine the valency which is multiplied by each element to get the molecular formula.

The equation used to calculate the valency is :

The empirical mass can be calculated from empirical formula and molar mass must be known.

Hence, the correct option is, (B) formula mass

plasma is the state of matter where the substance is ionized and has no definite shape or volume. the fact of being ionized makes the substance a good electrical conductor.