Chem I Worksheet #25 Empirical Formulas and Molecular Formulas Name _______________________

Vocabulary: empirical formula, molecular formula

Text Reference pg 229-233

1) Give the empirical formula that corresponds to each of the following molecular formulas:

a) sodium peroxide, Na₂O₂

b) terephthalic acid, C₈H₆O₄

c) phenobarbital, C₁₂H₁₂N₂O₃

d) 1,4-dichloro-2-butene, C₄H₆Cl₂

2) Analysis of a compound indicates that it contains 1.04 g K, 0.70 g of Cr, and 0.86 g of O. Find its empirical formula.

3) A compound is found to contain 36.48% Na, 25.41% S, and 38.11% O. Find its empirical formula.

4) Find the empirical formula of a compound that contains 53.70% iron and 46.30% sulfur.

5) When 2.004 g of calcium is heated in pure nitrogen gas, the sample gains 0.4670 g of nitrogen. Calculate the empirical formula of the calcium nitride formed.

6) How does the molecular formula of a compound differ from the empirical formula? Can a compound’s empirical and molecular formulas be the same? Explain and give an example?

7) A compound with the empirical formula CH₂O was found to have a molar mass of about 90 g/mole. What is the molecular formula of the compound?

8) A compound consists of 40.00% C, 6.713% H and 53.28% O on a mass basis and has a molar mass of about 180 g/mole. Determine the molecular formula of the compound.

9) A compound with the empirical formula C₂HF₄ was found to have a molar mass of about 200g/mole. What is the molecular formula of the compound?

10) Naphthalene is a soft solid that is often used in mothballs. Its molar mass is 128.18g/mole and it contains 93.75% carbon and 6.25% hydrogen by mass. Determine the empirical and molecular formulas of napthalene.