The Ksp (solubility product constant) of copper(II) chromate (CuCrO₄) is 3.6 x 10⁻⁶.
Understanding the Solubility Product Constant (Ksp)
The solubility product constant (Ksp) is a specific type of equilibrium constant that quantifies the solubility of a sparingly soluble ionic compound in a solution. When a solid ionic compound dissolves in water, it establishes an equilibrium between the undissolved solid and its dissociated ions in solution. The Ksp value represents the product of the molar concentrations of these ions, each raised to the power of their stoichiometric coefficients from the balanced dissolution equation. A higher Ksp value indicates greater solubility for the compound.
For copper(II) chromate, the dissolution equilibrium is represented as:
CuCrO₄(s) ⇌ Cu²⁺(aq) + CrO₄²⁻(aq)
The expression for its solubility product constant is therefore:
Ksp = [Cu²⁺][CrO₄²⁻]
Ksp Value of Copper(II) Chromate (CuCrO₄)
Based on established chemical data, the Ksp value for CuCrO₄ is 3.6 x 10⁻⁶. This value places CuCrO₄ among compounds considered sparingly soluble, meaning it dissolves to a small but measurable extent in water.
To provide context, here's a comparison of Ksp values for various chromates:
| Compound | Chemical Formula | Ksp Value |
|---|---|---|
| Barium Chromate | BaCrO₄ | 2.3 x 10⁻¹⁰ |
| Copper(II) Chromate | CuCrO₄ | 3.6 x 10⁻⁶ |
| Calcium Chromate | CaCrO₄ | 7.1 x 10⁻⁴ |
| Mercury(I) Chromate | Hg₂CrO₄ | 2.0 x 10⁻⁹ |
Analysis of Ksp Values:
- Relative Solubility: CuCrO₄ has a Ksp significantly higher than that of BaCrO₄ (2.3 x 10⁻¹⁰) and Hg₂CrO₄ (2.0 x 10⁻⁹). This indicates that copper(II) chromate is considerably more soluble in water compared to barium chromate or mercury(I) chromate.
- Comparison to Calcium Chromate: However, CaCrO₄ (7.1 x 10⁻⁴) exhibits the highest solubility among the listed chromates, being more soluble than CuCrO₄.
Practical Implications of Ksp Values
Understanding Ksp values is fundamental in several areas of chemistry:
- Predicting Precipitation: Ksp is critical for predicting whether a precipitate will form when two solutions containing potentially precipitating ions are mixed. If the ion product (Qsp) of the concentrations of the ions exceeds the Ksp, precipitation will occur until equilibrium is reached.
- Designing Separation Techniques: Differences in Ksp values are exploited in analytical chemistry for selective precipitation. This technique allows for the separation of specific ions from a mixture by carefully controlling the concentration of a precipitating agent. For example, if you had a solution containing both Cu²⁺ and Ba²⁺, you could selectively precipitate BaCrO₄ due to its much lower Ksp compared to CuCrO₄.
- Environmental Chemistry: Ksp values are vital for assessing the mobility and bioavailability of metal ions in environmental systems, such as soil and water. This information helps in developing strategies for pollution control and environmental remediation.
