Percent Composition and Molar Mass

The video tutorial explains percent composition by mass, using carbon dioxide (CO2) as an example. It details how to calculate the molar mass of CO2 and then determine the percent composition of carbon and oxygen in the molecule. The tutorial also introduces a shortcut for calculating percent composition when dealing with only two elements.

What is the basis for calculating percent composition?

• Mass

• Volume

• Number of atoms

• Density

Which molecule is used as an example to explain percent composition?

• Oxygen (O2)

• Water (H2O)

• Carbon Dioxide (CO2)

• Methane (CH4)

What is the molar mass of carbon used in the calculation?

• 18.02 grams per mole

• 16.00 grams per mole

• 12.01 grams per mole

• 14.01 grams per mole

How do you calculate the total molar mass of CO2?

• Add the masses of two carbons and two oxygens

• Add the masses of one carbon and two oxygens

• Add the masses of one carbon and one oxygen

• Add the masses of two carbons and one oxygen

What is the total molar mass of CO2?

• 28.02 grams per mole

• 44.01 grams per mole

• 32.00 grams per mole

• 18.02 grams per mole

What is the molar mass of oxygen used in the calculation?

• 12.01 grams per mole

• 14.01 grams per mole

• 18.02 grams per mole

• 16.00 grams per mole

What is the percent composition of carbon in CO2?

• 44.01%

• 50.00%

• 72.71%

• 27.29%

What is the percent composition of oxygen in CO2?

• 72.71%

• 27.29%

• 44.01%

• 50.00%

What is the shortcut method for finding the percent composition of the second element in a two-element molecule?

• Multiply the mass of the second element by 100

• Subtract the percent of the first element from 100%

• Divide the total mass by the mass of the first element

• Add the percent of the first element to 100%

Why might the shortcut method not work well for more complex molecules?

• It requires more than two elements

• It is only for ionic compounds

• It only works for gases

• It is only applicable to liquids