Unit 7: Percent Composition and Empirical Formula

​Ca₃(PO₄)₂

Multiple Choice

What is the percent by mass of oxygen in MgO?

• 20%
• 40%
• 50%
• 60%

Multiple Choice

What is the percent by mass of sodium in NaCl?

• 39%
• 61%
• 35%
• 65%

Multiple Choice

What is the percent composition by mass of sulfur (S) in the compound MgSO₄?

• 20.22%

• 19.85%

• 26.64%

• 28.64%

Multiple Choice

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

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

Multiple Choice

Which one is the empirical formula?

C₄H₆

• CH

• CH₃

• C₂H₃

• C₄H₆

Multiple Choice

What is the percent composition of a compound that contains 40.8 g carbon and 54.4 g oxygen?

• 42.9 %; 57.1% oxygen

• 52.9 %; 57.1% oxygen

• 42.9 %; 45.23% oxygen

• 55.9 %; 99.1% oxygen

Multiple Choice

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

• Mg₄N₃
• MgN₂
• Mg₃N₂ 
• MgN

Multiple Choice

What is the empirical formula if you have 88.80% copper and 11.20% oxygen?

• Cu₃O₈
• CuO₄
• Cu₂O
• Cu₄O₁₀