Understanding Light Absorption in CuSO₄ Solution

Copper sulfate (CuSO₄) solution appears blue because of its light absorption properties. The color we see is the complementary color to the one absorbed.

Step 1: Identify the Ion Responsible

The blue color comes from hydrated copper ions ${\left[\mathrm{Cu}\right(H_{2}O\left)6\right]}^{2+}$ in solution.

Step 2: Understand Absorption Spectrum

These ions absorb light in the orange-red region of the visible spectrum (approximately 600-800 nm wavelength).

Step 3: Apply Complementary Color Principle

Since orange-red light is absorbed, the transmitted light appears as its complementary color. The complementary color to orange-red is blue-green, but in practice, the solution appears blue due to the specific wavelengths involved.

Final Answer

The color of light absorbed by an aqueous solution of CuSO₄ is Orange-red.

Related Topics

• Coordination Chemistry
• Electronic Transitions in Transition Metals
• Beer-Lambert Law
• Colorimetry

Key Formulae and Theory

Beer-Lambert Law: $A=\epsilon cl$

Where A is absorbance, ε is molar absorptivity, c is concentration, and l is path length.

Complementary Colors: Colors opposite each other on the color wheel are complementary. When a substance absorbs one color, we perceive the complementary color.

Crystal Field Theory: Explains how d-d transitions in transition metal complexes lead to color absorption through splitting of d-orbitals.