Finding the Formula of a Hydrate from
Experimental Data
- State the purpose of the experiment: The
amount of water of hydration in copper sulfate hydrate was determined.
- Describe the procedure used: Three samples
of copper sulfate hydrate crystals were heated in a test tube over a Bunsen
burner. The samples were weighed before and after heating.
- Observe and record what happened:
a. Qualitatively: The blue crystals
turned into a white powder
- b. Quantitatively: (x is the
unknown): CuSO4 x H2O(s) --> CuSO4(s)
+ x H2O(l)
- Organize the data in tables or
graphs
| Sample |
mass hydrate |
mass CuSO4 |
mass H2O |
|
1 |
5.52
g |
3.53 g |
1.99
g |
| 2
|
4.62 g
|
2.94
g
|
1.68 g
|
|
3
|
3.05
g
|
1.70
g
|
1.35 g
|
- Process the data and find regularities
-
|
Sample |
mol
CuSO4 |
mol H2O |
mole ratio CuSO4/ H2O |
| 1 |
0.0221 |
0.110 |
1 / 4.98 |
| 2 |
0.0184 |
0.0932 |
1 / 5.07 |
|
3 |
0.0191 |
0.0943 |
1 / 4.94 |
- Interpret: There are 5 moles of water of
hydration per mole of CuSO4. The formula of the hydrate is
CuSO4. 5 H2O.
An EXAMPLE
for you to work out