AP Chemistry P.3
Crystal Growing and Empirical Formula Determination Lab
What is the ideal molarity of a cupric sulfate solution for growing crystals at room temperature?
Cupric sulfate and water form hydrous crystals when mixed together in a solution. This experiment will test the ideal molarity for growing these crystals at room temperature. Various amounts of cupric sulfate will create different molarities and in turn produces different size and numbers of crystals grown. The water is the controlled variable and the excess reactant in this experiment. The cupric sulfate salt will be dissolved in water, and left overnight to enable the crystals to grow. To determine the empirical formula of the crystals that were produced the largest one will be picked to be heated so that the water is derived off, and then the empirical formula can be determined.
CuSO4 (s) + xH2O (l)
Bunsen burner (hot plate)
2 Petri dishes
1. Mass out between 20-30 g. of CuSO4 salt in a beaker.
2. Using a graduated cylinder measure 50-mL of distilled water, and add it to the beaker containing the salt.
3. Heat this solution until all of the CuSO4 salt or the solute is dissolved completely.
4. Determine the new volume of the solution.
5. Take 2 Petri dishes and evenly distribute the solution into the dishes. Then place a cover onto one dish, leaving the other open.
6. Set these dishes aside, allowing them to sit overnight and enabling the crystals to form.
7. Calculate the molarity of the solution, and record it.
8. Clean station and equipment.
9. Next day, select a large crystal out of either Petri dish.
10. Mass an empty evaporating dish.
11. Mass the evaporating dish and the large crystal.
12. Place the...