Percent Composition and Empirical Formulas Review

What is the molar mass of Ca(OH)₂?

• 58.10 g/mol

• 73.09 g/mol

• 74.10 g/mol

• 114.18 g/mol

Calculate the molar mass for Al(OH)₃

• 78.0 g/mol

• 72 g/mol

• 28 g/mol

• 25 g/mol

What percentage of the total atomic mass of magnesium bromide (MgBr₂) is composed of bromine? Hint - consider the mass of both atoms of bromine in your calculation.

• 13%

• 43%

• 63%

• 87%

What is the percent composition by mass of sulfur in the compound MgSO₄ (gram formula mass = 120 g/mol)?

• 20%
• 27%
• 46%
• 53%

What is the percent composition of Benzene, C₆H₆?

• C = 50%
  H = 50%
• C = 85.7 %
  H = 14.3%
• C = 92.2%
  H = 7.8%
• C = 71.9%
  H = 28.1%

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

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

Which of the following is considered an empirical 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

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

• SO

• SO₂

• SO₃

• SO₄

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

• NaPO₂

• Na₂PO₃

• Na₃PO₄

• NaPO₄