The Mole Concept Test

Fill in the blanks with the most appropriate term.

6.02 x 102 is also called (1)_________________. The mass of one mole of any pure substance is called the (2)_________________ mass. For any element, this mass is equal to the atomic mass with the unit (3)_________________.
The (4)_________________ formula of a compound is the simplest whole number ratio of atoms, while the (5)_________________ formula of a compound represents the actual number of each atom in the compound.
(6)_________________ are compounds that crystallize from a water solution with water molecules clinging to the crystal particles.

Word Bank:
Avogadro’s number empirical grams/mole
hydrates molar molecular


Work each of the following problems, showing all work. These problems are representative of each type of problem worked in this unit.

1. Calculate the molar mass for ethane, C2H6.

3. Convert 4.77 x 1024 molecules of SO2 to grams.

4. What is the percentage composition of sodium hydroxide, NaOH?

5. A compound is found to contain 63% manganese, Mn, and 37% oxygen. What is the compound’s empirical formula?

6. What is the empirical formula for a substance if a 1.000 g sample of it contains 0.262 grams of nitrogen, 0.075 grams of hydrogen, and 0.663 grams of chlorine?

7. What is the molecular formula for a compound with an empirical formula of NO2 and a molar mass of 92.0 g/mol?

8. What is the formula for a hydrate that contains 6.4 g CuSO4 and 3.6 g H2O?

Click here to check your answers:

1. Avogadro’s number
2. molar
3. grams/mole
4. empirical
5. molecular
6. Hydrates

1. C2H6 2(12.0 g) + 6 (1.0 g) = 30.0 g