The equation for the decomposition reaction of copper sulfate pentahydrate is CuSO₄ ⋅ 5H₂O (s) → CuSO₄ (s) + 5H₂O (g). This reaction occurs when the hydrated compound is heated, leading to the release of its water of hydration.
Understanding the Decomposition Process
Copper sulfate pentahydrate (CuSO₄ ⋅ 5H₂O) is a common hydrated salt, characterized by its vibrant medium blue color. When this compound is subjected to heat, it undergoes a chemical change known as thermal decomposition, specifically a dehydration reaction. During this process, the water molecules that are chemically bonded within the crystal structure are released.
The heat energy provided breaks the bonds holding the water molecules to the copper sulfate, causing them to escape as water vapor (gas). The remaining solid is anhydrous copper sulfate (CuSO₄), which is distinctly light blue or almost white in appearance, signifying the removal of the water of hydration.
Reactants and Products Overview
The table below summarizes the key components involved in this chemical transformation:
| Component | Chemical Formula | Physical State | Color (Typical) | Description |
|---|---|---|---|---|
| Reactant: | ||||
| Copper Sulfate Pentahydrate | CuSO₄ ⋅ 5H₂O | Solid (s) | Medium Blue | The hydrated form, stable at room temperature. |
| Products: | ||||
| Anhydrous Copper Sulfate | CuSO₄ | Solid (s) | Light Blue | The dehydrated form, resulting from water removal. |
| Water | H₂O | Gas (g) | Colorless | Released as water vapor during heating. |
Practical Aspects and Observations
This decomposition reaction is a classic example of a reversible chemical process and has several practical implications:
- Color Change: The distinct color change from medium blue to light blue (or white) serves as a visual indicator that the dehydration has occurred. This color transition is often used in chemistry demonstrations to illustrate the concept of water of crystallization.
- Test for Water: Anhydrous copper sulfate, being hygroscopic (water-absorbing), can be used as a test for the presence of water. If water is added to the light blue anhydrous form, it will rehydrate and turn back to its characteristic medium blue color.
- Industrial Applications: Understanding such dehydration processes is crucial in various industrial applications, including the purification of chemicals and the preparation of anhydrous salts for specific reactions where water presence is undesirable.
