Question

Mercury chloride is a commercial fungicide. If the molar mass is 470 g/mol and the percent composition is 85.0% Hg and 15.0% Cl, what is the empirical and molecular formula of the fungicide?

Answer 1

Data: molar mass 470 g/mol

Percent composition:

Hg = 85.0%
Cl = 15.0%

Solution:

1)  Convert % to molar ratios

A. Base: 100 g

=> Hg = 85.0 g / 200.59 g/mol = 0.4235 mol

     Cl = 15.0 g / 35.45 g/mol = 0.4231 mol

B. divide by the higher number and round to whole number

Hg = 0.4325 / 0.4231 = 1.00

Cl = 0.4231 / 0.4231 = 1.00

=> Empirical formula = Hg Cl

2) Find the mass of the empirical formula:

HgCl: 200.59 g/mol + 35.45 g/mol = 236.04

3) Determine how many times is the empirical mass contained in the molecular mass:

470 g/mol / 236.04 = 1.99 ≈ 2

=> Molecular formula = Hg2 Cl2.

Answers:

Empirical formula HgCl
Molecular Formula Hg2Cl2