Molecular Mass and Mole Concepts and Problems

1. What is Avogadro’s number (Nₐ)?

9.81 6.022 × 10²³ 3.14 × 10²³ 1.602 × 10⁻¹⁹

2. How many moles of Ne are in 10.2 g of Ne?

1.02 mol Ne 5.07 mol Ne 0.102 mol Ne 0.507 mol Ne

3. What is molecular mass (or molecular weight)?

The total mass of a molecule expressed in atomic mass units (amu) The number of molecules in a mole The number of atoms in a molecule The mass of one atom

4. What is a mole (n)?

Mass of one molecule Quantity of substance containing as many elementary entities as atoms in exactly 12 grams of carbon-12 Mass of one atom Number of atoms in one molecule

5. What is the molar mass of an atom?

Mass of 1 mole of atoms (g) Mass of 1 atom (amu) Number of atoms in a molecule Mass of 1 molecule (g)

6. How many grams of Fe are in 2.5 moles of Fe?

250 g Fe 100 g Fe 139.6 g Fe 55.8 g Fe

7. How many oxygen atoms are present in 18.0 g of H₂O?

1.00 × 10²³ oxygen atoms 12.04 × 10²³ oxygen atoms 6.02 × 10²³ oxygen atoms 3.01 × 10²³ oxygen atoms

8. How many moles of CO₂ are present in 22.4 g of CO₂?

0.507 mol CO₂ 1.00 mol CO₂ 2.24 mol CO₂ 0.224 mol CO₂

9. What is the formula for calculating molecular mass?

Sum of electrons in the molecule Sum of protons and neutrons Sum of atomic numbers of all atoms Sum of (atomic mass of each element × number of atoms of that element)

10. How many atoms are in 16.3 g of S?

1.00 × 10²³ S atoms 6.02 × 10²³ S atoms 3.06 × 10²³ S atoms 2.00 × 10²³ S atoms