Molecular Mass and Mole Concepts and Problems

1. What is the molar mass of an atom?

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

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

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

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

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

4. What is the formula for calculating molecular mass?

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

5. 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

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

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

7. 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 Number of atoms in one molecule Mass of one atom

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

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

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

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

10. What is Avogadro’s number (Nₐ)?

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