Percent Composition, Empirical Formula, and Molecular Formula

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

• Mg₄N₃
• MgN₂
• Mg₃N₂ 
• MgN

Find the percent composition of Cu₂S?

• %Cu= 67.987 %S= 32.013
• %Cu= 79.854   %S= 20.145
• %Cu= 35.946   %S= 64.054

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

• CH₂O
• C₂H₄O₂
• C₄H₈O₄
• C₆H₁₂O₆

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

•  NaPO2
• Na2PO3
• Na3PO4
• NaPO4

What is the molecular formula for a compound with the empirical formula: K₂SO₄ and a molecular mass of 696g.

• K₂SO₄ 
• K₈SO₁₆
• K₈S₄O₈ 
• K₈S₄O₁₆ 

What is the empirical formula if you have 81.82% carbon and 18.18% hydrogen?

• C3H8
• CH4
• C2H2
• C4H10

A formula with the lowest whole # ratio of elements in a compound is called

• Molecular Formula
• Chemical Formula
• Empirical Formula 
• Distance Formula

What is the percentage of chlorine in sodium chloride? (NaCl)

• 60.7%
• 39.3%
• 60%
• 40%

What is the percent by mass of oxygen in MgO?

• 20%
• 40%
• 50%
• 60%

Which pair has the same empirical formula?

• NaCrO₄ and Na₂Cr₂O₇
• C₂H₄O₂ and C₆H₁₂O₆
• C₃H₆O₃ and C₂H₆O₂
• CH₄ and C₂H₆