7.4: Percent Composition and Empirical Formula

Multiple Choice

What is the percent by mass of oxygen in MgO? Hint: The attached image is an example of a worked problem other than this one.

• 20%

• 40%

• 50%

• 60%

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

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

• SO
• SO2
• SO3
• SO4