Percent Composition Practice

What percent of 40 is 15?

• 375%

• 2.67%

• 267%

• 37.5%

You ate 3 eggs for breakfast out of a dozen. What percentage of the eggs did you eat?

• 25%

• 3%

• 100%

• 75%

A mineral sample contains many elements, but has a large amount of copper in it. The sample has a mass of 6.0 g and the copper in the sample has a mass of 5.5 g. What is the percentage of copper in the sample?

• 33%

• 102%

• 0.92%

• 92%

What is the percent by mass of oxygen in MgO?

• 20%
• 40%
• 50%
• 60%

What is the percent by mass of magnesium in MgO?

• 20%
• 40%
• 50%
• 60%

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

• 20%
• 27%
• 46%
• 53%

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 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%

Which element has an abundance of 39.03% in the compound sodium phosphate, Na₃PO₄

• Na

• P

• O

• None of the above

Carbon monoxide, a deadly gas, has a chemical formula of CO (one carbon atom with one oxygen atom). If you look at the total atomic mass of CO, does carbon or oxygen make up more of the mass?

• carbon

• oxygen

• they are exactly the same

• it is impossible to tell