Percent Composition and Atomic Mass

The video tutorial explains how to find the percent composition by mass of each element in copper II sulfate (CuSO4). It covers the calculation process for copper, sulfur, and oxygen, using their molar masses and the overall molar mass of CuSO4. The tutorial emphasizes multiplying by 100 to convert to a percentage and notes that the sum of percentages should be close to 100%.

What is the first step in finding the percent composition by mass of an element in a compound?

• Divide the atomic mass by the number of atoms

• Multiply the atomic mass by the number of atoms

• Subtract the atomic mass from the molar mass

• Add the atomic mass to the molar mass

How many copper atoms are present in copper II sulfate?

• Two

• Three

• One

• Four

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

• 63.55 grams per mole

• 64.55 grams per mole

• 62.55 grams per mole

• 65.55 grams per mole

What is the percent composition by mass of copper in copper II sulfate?

• 29.88%

• 49.88%

• 39.88%

• 59.88%

How many sulfur atoms are present in copper II sulfate?

• Four

• One

• Three

• Two

What is the percent composition by mass of sulfur in copper II sulfate?

• 20.01%

• 10.01%

• 30.01%

• 40.01%

How many oxygen atoms are present in copper II sulfate?

• Five

• Four

• Three

• Two

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

• 17 grams per mole

• 14 grams per mole

• 15 grams per mole

• 16 grams per mole

What is the percent composition by mass of oxygen in copper II sulfate?

• 60.10%

• 40.10%

• 30.10%

• 50.10%

What should the sum of the percent compositions of all elements in copper II sulfate be approximately?

• 105%

• 99.9%

• 95%

• 90%