Percent Composition Empirical and Molecular Formulas

Given the following: 42.07% Na, 18.89% P, and 39.04% O, determine the empirical formula.

•  NaPO2

• Na2PO3

• Na3PO4

• NaPO4

A compound consists of 72.2% magnesium(Mg) and 27.8% nitrogen(N) by mass. What is the empirical formula?

• Mg₄N₃

• MgN₂

• Mg₃N₂ 

• MgN

You are given the following percentages: 40.05% S and 59.95% O. Find the empirical formula for these elements.

• SO

• SO2

• SO3

• SO4

What is the molecular formula if the empirical formula is CH₂O and the molecular molar mass is 180.18?

• CH₂O

• C₂H₄O₂

• C₄H₈O₄

• C₆H₁₂O₆

What is the empirical formula for a compound if it contains 70% iron (Fe) and 30% oxygen (O) by mass? Assume atomic masses: Fe = 56 g/mol, O = 16 g/mol.

• FeO

Tags

NGSS.HS-PS1-7

Complete the formula for % Composition.

a

b

c

total mass of compound

100

mass of element

A compound contains 40% sulfur and 60% oxygen by mass. What is the empirical formula of the compound? Assume the molar mass of sulfur (S) is 32 g/mol and oxygen (O) is 16 g/mol.

• SO

• 25%

• 20%

• 75%

• 14.3%

• 5

• 7

• 10

• 12

(Page 38-40) Complete the formula for % Composition.

a

b

c

mass of element

total mass of compound

100