Molar Mass and Atomic Calculations

The video tutorial covers calculating the average atomic mass of elements like bromine and boron, determining isotope abundance, understanding and calculating molar mass, converting between grams, moles, and atoms, and finding the mass percent composition of elements in compounds. It provides step-by-step examples and explanations to help learners grasp these fundamental chemistry concepts.

What is the average atomic mass of bromine if the isotopes have masses of 78.9183 amu and 80.9163 amu with abundances of 50.69% and 49.31% respectively?

• 81.00 amu

• 80.92 amu

• 79.90 amu

• 78.92 amu

If the average atomic mass of boron is 10.81 amu, what is the percent abundance of the isotope B10 if B11 is 80% abundant?

• 70%

• 20%

• 30%

• 50%

How many B10 atoms are there in a sample of 600 boron atoms if B10 is 20% abundant?

• 240

• 120

• 480

• 60

What is the molar mass of potassium fluoride (KF) if the atomic masses of potassium and fluorine are 39.1 and 19 respectively?

• 98.1 g/mol

• 118.1 g/mol

• 78.1 g/mol

• 58.1 g/mol

How many moles are in 72 grams of methane (CH4) if its molar mass is 16.042 g/mol?

• 3.5 moles

• 5.5 moles

• 2.5 moles

• 4.5 moles

How many grams are in 2.5 moles of NO2 if its molar mass is 46.01 g/mol?

• 92.02 grams

• 161.04 grams

• 138.03 grams

• 115.00 grams

How many atoms of carbon are present in 7.2 moles of carbon?

• 7.3358 x 10^24 atoms

• 4.3358 x 10^24 atoms

• 5.3358 x 10^24 atoms

• 6.3358 x 10^24 atoms

How many grams are in 4.6 x 10^23 atoms of nickel if 1 mole of nickel is 6.022 x 10^23 atoms?

• 2.7639 grams

• 1.7639 grams

• 3.7639 grams

• 0.7639 grams

What is the mass of 25 carbon atoms in atomic mass units (amu) if the atomic mass of carbon is 12.01 amu?

• 300.25 amu

• 301.25 amu

• 302.25 amu

• 303.25 amu

What is the percent composition by mass of carbon in C6H12O6 if its molar mass is 180.156 g/mol?

• 50%

• 60%

• 40%

• 70%