The speration of lanthanides by ion exchanges method is based on

Options

A. Size of the ions
B. Oxidation state of the ions
C. The solubility of their nitrates
D. basicity of hydroxides of lanthanides

Answer

To solve the question regarding the separation of lanthanides by the ion exchange method, we will analyze the options provided and determine the correct basis for this separation.

### Step-by-Step Solution:

1. **Understanding Ion Exchange Method**:
- The ion exchange method is a widely used technique for separating ions based on their charge and size. It involves the use of synthetic resins that can exchange ions with the solution.

2. **Analyzing the Options**:
- We have four options to consider:
- A) Size of the ions
- B) Oxidation state of the ions
- C) Solubility of the nitrates
- D) Basicity of hydroxides of lanthanides

3. **Evaluating Each Option**:
- **Option A: Size of the ions**:
- The size of the ions is crucial in the ion exchange process. Smaller ions can fit better into the resin and have a stronger interaction with it. This is particularly important for lanthanides, which exhibit lanthanide contraction, leading to smaller ionic radii.
- **Option B: Oxidation state of the ions**:
- While oxidation states can influence the chemical behavior of ions, they do not directly affect the ion exchange process in this context.
- **Option C: Solubility of the nitrates**:
- The solubility of nitrates does not play a significant role in the ion exchange method; it is more about the interaction of ions with the resin.
- **Option D: Basicity of hydroxides of lanthanides**:
- Basicity is not a factor in the ion exchange method for separating lanthanides.

4. **Conclusion**:
- Based on the analysis, the correct answer is **A) Size of the ions**. The separation of lanthanides by the ion exchange method is primarily based on the size of the ions, as smaller ions adhere better to the resin used in the process.

### Final Answer:
The separation of lanthanides by ion exchange method is based on **the size of the ions**.