Empirical Formula of a Hydrate Simulation

When copper (II) sulfate hydrate, a blue crystalline solid containing embedded water molecules (called a hydrate), is heated in air, it loses the water molecules and the blue solid is transformed to a white anhydrous (no water) crystal known as copper (II) sulfate.

PURPOSE: Use the computer simulation to determine

a) the percentage of water in copper (II) sulfate hydrate

b) determine the number of water molecules per unit of copper(II)sulfate hydrate: CuSO4 X H2O. Determine the whole number value of the "X".

The computer simulation can be found at the following URL:

http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/stoichiometry/empirical.html

(You can also google “green bowe” simulations and scroll down to Percent Composition Simulation under the Stoichiometry Section)

PROCEDURE

1.  Click the gold arrow.

2.  Record the initial mass of the hydrate(ionic compound & water combined) in the data section

3.  Click the arrow gray arrow to start heating.

4.  Wait for the final mass to pop up on the screen and record the mass of the anhydrate (ionic compound only) in the data section.

5.  Copy the chemical reaction in red and list a qualitative observtion of the reaction in the data section

DATA

Chemical Reaction:

Observations of Reaction

Mass of hydrate (CuSO4 & H2O) BEFORE
Mass of anhydrate (CuSO4) AFTER

CALCULATIONS: You must show the equation if applicable, the substituted numbers into the equation and the correct answer with units & proper significant units

Percent Composition

Calculations:

1.  Determine the mass of water removed from the sample.

2.  Determine the % composition of water in the sample using your lab data.

Empirical Formula

Calculations

1.  Calculate the moles of H2O that were driven off.

2.  Calculate the mass of CuSO4 present (what is left in the crucible).

3.  Calculate the moles of CuSO4 present.

4.  Determine the SIMPLEST ratio of moles of CuSO4 to moles of water.

5.  Use the ratio to write the complete formula for copper (II) sulfate hydrate, __CuSO4 __ H2O. The ratio of moles usually refers to the subscripts of the

formula but in a hydrate, they are the coefficients of the salt and the water

ANALYSIS

1.  What does the triangle above the yield sign mean?

2.  List the chemical formula for the hydrate and the anhydrate.

3.  What would happen to the color of the anhydrous sample if a small amount (0.2ml) of water is added to it?

4.  What type of bonding is used between the Cu2+ cation and the SO42- anion, in CuSO4 (ionic, metallic, covalent...)?

5.  If Epson salt , MgSO4∙ X H2O is heated to 250ºC, all the water of hydration is lost. On heating 1.687 g sample of the hydrate,

.824 g of MgSO4 remains. What if the formula for Epson Salt? Show work!!