Percent Composition and Molar Mass

The video tutorial explains how to find the percent composition by mass for each element in calcium nitrate (Ca(NO3)2). It begins with calculating the molar mass of the compound, followed by determining the percent composition of calcium, nitrogen, and oxygen. The tutorial provides step-by-step calculations and concludes with a summary of the results.

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

• Measure the volume of the compound

• Find the atomic number of each element

• Calculate the molar mass of the compound

• Determine the number of atoms in the compound

What is the molar mass of calcium nitrate (Ca(NO3)2)?

• 150.50 grams per mole

• 200.20 grams per mole

• 100.10 grams per mole

• 164.10 grams per mole

How many calcium atoms are present in calcium nitrate?

• One

• Four

• Three

• Two

What is the percent composition of calcium in calcium nitrate?

• 24.42%

• 50.00%

• 10.00%

• 30.00%

How many nitrogen atoms are present in calcium nitrate?

• Three

• Four

• Two

• One

What is the percent composition of nitrogen in calcium nitrate?

• 17.07%

• 20.00%

• 25.00%

• 15.00%

How many oxygen atoms are present in calcium nitrate?

• Seven

• Four

• Six

• Five

What is the percent composition of oxygen in calcium nitrate?

• 55.00%

• 60.00%

• 50.00%

• 58.50%

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

• 95%

• 90%

• 100%

• 110%

Why might the total percent composition not exactly equal 100%?

• Due to measurement errors

• Due to rounding errors

• Because of incorrect calculations

• Because of missing elements