Percent Composition and Atomic Counts

The video tutorial explains how to calculate the percent composition by mass of each element in sodium sulfate (Na2SO4). It begins by introducing the concept and formula for percent composition. The tutorial then provides step-by-step calculations for sodium, sulfur, and oxygen, using their respective molar masses and the total molar mass of Na2SO4. The video concludes by summarizing the results and ensuring the calculated percentages add up to approximately 100%.

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

• Multiply the atomic mass by the number of atoms

• Divide the atomic mass by the molar mass

• Add the atomic masses of all elements

• Subtract the atomic mass from the molar mass

How many sodium atoms are present in Na2SO4?

• Four

• Three

• Two

• One

What is the molar mass of sodium sulfate (Na2SO4) used in the calculations?

• 120.04 g/mol

• 142.04 g/mol

• 160.04 g/mol

• 180.04 g/mol

What is the percent composition by mass of sodium in Na2SO4?

• 99.99%

• 45.06%

• 32.37%

• 22.56%

How many sulfur atoms are present in Na2SO4?

• Four

• Three

• Two

• One

What is the percent composition by mass of sulfur in Na2SO4?

• 99.99%

• 22.56%

• 45.06%

• 32.37%

How many oxygen atoms are present in Na2SO4?

• One

• Two

• Three

• Four

What is the percent composition by mass of oxygen in Na2SO4?

• 99.99%

• 45.06%

• 32.37%

• 22.56%

What should the total percent composition of all elements in a compound add up to?

• 150%

• 100%

• 75%

• 50%

What is the acceptable total percent composition for Na2SO4 as mentioned in the video?

• 99.99%

• 98.00%

• 100.00%

• 101.00%