Calculating Percent Composition in Chemistry

This video tutorial by Mr. Millings explains how to calculate the percent composition by mass of different compounds and molecules. It begins with a basic example using marbles to illustrate the concept of percentage calculation. The tutorial then applies this concept to chemical compounds, demonstrating how to calculate the percent composition of elements in water, glucose, and ammonium sulfate. The video emphasizes the importance of understanding the part-to-whole relationship and using the periodic table for atomic masses.

What is the first step in calculating the percentage composition by mass?

• Identify the total mass of the compound.

• Understand the concept of a percentage.

• Determine the mass of each element in the compound.

• Calculate the total number of moles.

How many total marbles were in the jar used in the example?

• 35 marbles

• 40 marbles

• 25 marbles

• 30 marbles

What percentage of a water molecule's mass is oxygen?

• 25%

• 11.2%

• 88.8%

• 50%

What is the total mass of a water molecule?

• 16.00 g/mol

• 18.02 g/mol

• 20.00 g/mol

• 22.02 g/mol

What is the mass percent of carbon in glucose?

• 10%

• 39.99%

• 50%

• 25%

What is the molar mass of glucose?

• 180.18 g/mol

• 160.18 g/mol

• 200.18 g/mol

• 180.18 amu

What element in ammonium sulfate has the highest mass percent?

• Nitrogen

• Hydrogen

• Sulfur

• Oxygen

What is the total mass of ammonium sulfate?

• 132.17 g/mol

• 132.17 amu

• 150.00 g/mol

• 120.00 g/mol

How is the percentage of an element in a compound generally calculated?

• Total moles divided by element's moles times 100%

• Element's moles divided by total moles times 100%

• Total mass divided by element's mass times 100%

• Element's mass divided by total mass times 100%

Which of the following is not a step in calculating percent composition by mass?

• Determining the mass of each element.

• Multiplying the mass ratio by 100.

• Calculating the total mass of the compound.

• Calculating the density of each element.