Percent Composition in Chemistry

Dr. Kent explains how to calculate the percent composition of compounds by mass. He provides examples using water, H2S, glucose, and iron(II) phosphate, demonstrating the calculation process for each element in the compounds. The video emphasizes the importance of adding percentages to ensure they sum to 100% and discusses significant figures in calculations.

What does percent composition measure in a compound?

• The percentage of each element by density

• The percentage of each element by mass

• The percentage of each element by volume

• The percentage of each element by molarity

How do you calculate the percent composition of an element in a compound?

• Divide the molar mass of the element by the molar mass of the compound and multiply by 100

• Multiply the molar mass of the element by the molar mass of the compound

• Add the molar mass of the element to the molar mass of the compound

• Subtract the molar mass of the element from the molar mass of the compound

What is the molar mass of H2S?

• 16.04 g/mol

• 18.02 g/mol

• 32.07 g/mol

• 34.09 g/mol

What percentage of H2S is sulfur by mass?

• 0.07%

• 94.07%

• 5.93%

• 32.07%

What is the total mass of carbon in glucose?

• 180.18 g

• 96.0 g

• 12.2 g

• 72.6 g

What is the percentage of oxygen in glucose?

• 6.727%

• 39.99%

• 53.28%

• 100%

How many atoms of oxygen are in glucose?

• 8

• 4

• 6

• 12

What is the molar mass of iron(II) phosphate?

• 61.94 g/mol

• 167.55 g/mol

• 128.00 g/mol

• 357.49 g/mol

What percentage of iron(II) phosphate is iron by mass?

• 46.868%

• 100%

• 17.33%

• 35.805%

What is the percentage of phosphorus in iron(II) phosphate?

• 17.33%

• 46.868%

• 35.805%

• 100%