Percent Composition and Atomic Counts

The video tutorial explains how to calculate the percent composition by mass of each element in lead(II) nitrate (Pb(NO3)2). It covers the general formula for percent composition, using the molar mass of each element and the total molar mass of the compound. The tutorial provides step-by-step calculations for lead, nitrogen, and oxygen, showing how to multiply the molar mass by the number of atoms, divide by the compound's molar mass, and multiply by 100 to get the percentage. The video concludes by ensuring the sum of percentages is close to 100%.

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

• Add the atomic masses of all elements

• Subtract the atomic number from the molar mass

• Multiply the molar mass by the number of atoms

• Divide the total mass by the number of atoms

What is the molar mass of lead (Pb) used in the calculation for Pb(NO3)2?

• 100.0 grams per mole

• 16.00 grams per mole

• 14.01 grams per mole

• 207.2 grams per mole

How many lead atoms are present in Pb(NO3)2?

• Four

• Three

• One

• Two

What is the percent composition of lead in Pb(NO3)2?

• 29.0%

• 8.46%

• 50.0%

• 62.5%

How many nitrogen atoms are there in Pb(NO3)2?

• Four

• Three

• Two

• One

What is the percent composition of nitrogen in Pb(NO3)2?

• 62.5%

• 8.46%

• 29.0%

• 14.01%

How many oxygen atoms are present in Pb(NO3)2?

• Eight

• Six

• Four

• Two

What is the percent composition of oxygen in Pb(NO3)2?

• 16.00%

• 62.5%

• 8.46%

• 29.0%

What should the sum of the percent compositions of all elements in a compound be approximately?

• 50%

• 75%

• 150%

• 100%

Who is the presenter of the video tutorial?

• Dr. A

• Dr. D

• Dr. C

• Dr. B