AP Chemistry Lab

by Kirsten S., Jonathan B., Daniel S., & Sabrina H.

The Determination of a Chemical Formula


Separate the components of a copper chloride hydrate sample in order to measure the mass of each. This is done by evaporating the water and conducting a chemical reaction between the copper chloride and aluminum. The calculated masses will be used to determine the empirical formula of the compound.


  • Crucible
  • Ring stand and clay triangle
  • 50 mL beaker
  • Funnel
  • Unknown solid copper chloride hydrate
  • Aluminum Wire (20 gauge)
  • 6 M hydrochloric acid solution
  • Distilled water
  • Spatula
  • Balance



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Data Analysis

How many moles of water were in the sample?

0.22 g H2O * 1 mol H2O/18.02 g H2O = 0.012 mol H2O

How many moles of copper were in the sample?

0.22 g Cu * 1 mol Cu/ 63.55 g Cu = 0.006 mol Cu

How many moles of chlorine were in the sample?

0.22 g Cl * 1 mol Cl/ 35.45 g Cl = 0.011 mol Cl

What is the empirical formula for the compound?

0.012 mol H2O / 0.006 = 2

0.006 mol Cu / 0.006 = 1

0.011 mol Cl / 0.006 = 1.83 (~2)


Error Discussion

From our experiment, we encountered various instances that may have resulted in miscalculations. When we heated the solution, we may not have properly removed all of the water within the compound and some of the chlorine was likely evaporated (resulting in the reduction during our calculations). Some more common errors included rounding and failure to completely remove all of the copper chloride sample from the crucible, resulting in a lower amount of total moles (1.8 instead of 2).