Assertion : `La(OH)_3` is more basic than `Lu(OH)_3` .
Reason : Basic character of hydroxides of lanthanoids decrease on moving from `La^(3+)` to `Lu^(3+)`

Options

A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understanding the Assertion
The assertion states that `La(OH)₃` is more basic than `Lu(OH)₃`.

**Hint:** Basicity of hydroxides generally depends on the ionic size and the ability of the cation to stabilize the hydroxide ion.

### Step 2: Understanding the Reason
The reason provided states that the basic character of hydroxides of lanthanides decreases as we move from `La³⁺` to `Lu³⁺`.

**Hint:** Consider how the size of the cation affects the covalent character of the hydroxides and their ability to donate hydroxide ions.

### Step 3: Analyzing the Trend in Lanthanides
As we move from `La³⁺` to `Lu³⁺`, the ionic size decreases due to lanthanide contraction. This means that `Lu³⁺` is smaller than `La³⁺`.

**Hint:** Remember that smaller cations tend to have a higher charge density, which can lead to increased covalent character in their compounds.

### Step 4: Covalent Character and Basicity
With the decrease in size from `La³⁺` to `Lu³⁺`, the covalent character of the hydroxides increases. Increased covalent character means that the hydroxides are less likely to dissociate and release hydroxide ions, leading to decreased basicity.

**Hint:** Think about how covalent character affects the solubility and ionization of hydroxides in water.

### Step 5: Conclusion
Since `La(OH)₃` has a more ionic character compared to `Lu(OH)₃`, it is more basic. Therefore, both the assertion and the reason are correct, and the reason correctly explains the assertion.

**Final Answer:** Both the assertion and the reason are correct, and the reason is the correct explanation of the assertion.