Wavelength of red light is absorbed by the complex

Options

A. `[Cu(CN)_(4)]^(2-)`
B. `[Cu(NH_(3))_(4)]^(2=0`
C. `CuSO_(4)`
D. `Cu(CN)_(2)`

Explanation

To solve the question regarding which complex absorbs the wavelength of red light, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Absorption of Light by Complexes**:
- Different metal complexes absorb different wavelengths of light. The color of light absorbed is complementary to the color observed.

2. **Identifying the Complex in Question**:
- The question involves complexes that can absorb red light. Red light has a longer wavelength, and its absorption typically results in the transmission of colors that are complementary to red.

3. **Analyzing the Reaction with Ammonium Hydroxide**:
- When ammonium hydroxide (NH4OH) is added to a solution containing copper(II) ions (Cu²⁺), a deep blue solution is formed. This indicates that the complex formed absorbs light in the red region of the spectrum.

4. **Writing the Reaction**:
- The reaction can be represented as:
\[ \text{Cu}^{2+} + 4 \text{NH}_4\text{OH} \rightarrow \text{Cu(NH}_3\text{)}_4^{2+} + 4 \text{OH}^- \]
- The resulting complex is \(\text{Cu(NH}_3\text{)}_4^{2+}\), which is deep blue.

5. **Understanding Color Transmission**:
- Since the complex absorbs red light, it transmits greenish-blue light, which is the complementary color to red.

6. **Evaluating the Options**:
- Based on the information provided, we need to evaluate the options given in the question. The correct complex that absorbs red light and appears blue is \(\text{Cu(NH}_3\text{)}_4^{2+}\).

7. **Final Conclusion**:
- The complex that absorbs the wavelength of red light is \(\text{Cu(NH}_3\text{)}_4^{2+}\), making it the correct answer.