Percent Composition/Molecular Mass

What is the percent by mass of magnesium in MgO?

• 20%
• 40%
• 50%
• 60%

What is the percent by mass of sodium in NaCl?

• 39%
• 61%
• 35%
• 65%

What percentage of the total atomic mass of carbon monoxide (CO) is composed of carbon?

• 29%

• 43%

• 57%

• 73%

What is the percent by mass of fluorine in CaF₂ (gram-formula mass = 78 g/mol)?

• 24%
• 49%
• 51%
• 65%

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

• 20%
• 27%
• 46%
• 53%

What percentage of the total atomic mass of magnesium bromide (MgBr₂) is composed of magnesium?

• 13%

• 43%

• 63%

• 87%

What percentage of the total atomic mass of lithium phosphide (Li₃P) is composed of phosphorus?

• 13%

• 29%

• 40%

• 60%

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%

Find the percentage composition of Mg in Mg₃(PO₄)₂.

• 27.48% Mg

• 43.11% Mg

• 16.00% Mg

• 12.63% Mg

What is the percent by mass of Cu in CuBr₂?

• 50%

• 71.6%

• 28.4%

• 44.3%