Percent Composition and Chemical Mass

This video tutorial explains the concept of percent composition, which is the percentage by mass of each element in a compound. It uses water (H2O) as an example to demonstrate how to calculate the percent composition of hydrogen and oxygen. The tutorial also provides a general formula for calculating percent composition and illustrates its application using experimental data. The lesson concludes with a summary and encourages students to bring any questions to class.

What does percent composition represent in a substance?

• The mass of each element in a substance

• The volume of each element in a substance

• The number of atoms of each element in a substance

• The density of each element in a substance

What is the mass of water (H2O) in grams per mole?

• 20 g per mole

• 16 g per mole

• 18 g per mole

• 22 g per mole

How many grams per mole is the mass of hydrogen?

• 4 g per mole

• 3 g per mole

• 2 g per mole

• 1 g per mole

What percentage of water's mass is hydrogen?

• 10%

• 12%

• 11%

• 13%

What is the general formula for calculating the percent mass of an element in a compound?

• Mass of element * Total mass of compound / 100

• Total mass of compound / Mass of element * 100

• Mass of element / Total mass of compound * 100

• Total mass of compound * Mass of element / 100

What does a percentage represent in general?

• A ratio of two whole numbers

• A fraction or part of a whole

• A whole number

• A decimal number

In the experimental data example, what is the total mass of the substance?

• 55 g

• 45 g

• 40 g

• 50 g

How many grams of nitrogen are present in the experimental data example?

• 10 g

• 12 g

• 15 g

• 13 g

What is the percent composition of nitrogen in the experimental data example?

• 26%

• 25%

• 30%

• 20%

What should you do if you have any questions from the lesson?

• Ignore them

• Search online

• Ask a friend

• Write them down and bring them to class