Assertion : Higher order ionization constants `(K_(a_(2)),K_(a_(3)))` are smaller than the lower order ionization constant `(K_(a_(1)))` of polyprotic acid.
Reason : Polyprotic acid solutions contain a mixture of acids.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the question regarding the assertion and reason related to polyprotic acids, we will break down the concepts step by step.

### Step 1: Understanding Polyprotic Acids
Polyprotic acids are acids that can donate more than one proton (H⁺) per molecule. For example, phosphoric acid (H₃PO₄) can donate three protons in a stepwise manner:
1. H₃PO₄ ⇌ H₂PO₄⁻ + H⁺ (first ionization, Kₐ₁)
2. H₂PO₄⁻ ⇌ HPO₄²⁻ + H⁺ (second ionization, Kₐ₂)
3. HPO₄²⁻ ⇌ PO₄³⁻ + H⁺ (third ionization, Kₐ₃)

### Step 2: Comparing Ionization Constants
The assertion states that the higher order ionization constants (Kₐ₂ and Kₐ₃) are smaller than the lower order ionization constant (Kₐ₁). This is true due to the nature of the ionization process:
- The first ionization involves the removal of a proton from a neutral molecule (H₃PO₄), which is relatively easier.
- The second and third ionizations involve removing protons from negatively charged species (H₂PO₄⁻ and HPO₄²⁻, respectively). This process is more difficult because it leads to the formation of more negatively charged species, which are less stable.

### Step 3: Conclusion on Assertion
Since it is more difficult to remove protons from negatively charged species, we conclude that:
- Kₐ₁ > Kₐ₂ > Kₐ₃
Thus, the assertion is true.

### Step 4: Evaluating the Reason
The reason states that polyprotic acid solutions contain a mixture of acids. This is also true, as in a solution of a polyprotic acid like H₃PO₄, you will have a mixture of H₃PO₄, H₂PO₄⁻, HPO₄²⁻, and PO₄³⁻ present in equilibrium.

### Step 5: Analyzing the Relationship
While both the assertion and reason are true, the reason does not explain why Kₐ₂ and Kₐ₃ are smaller than Kₐ₁. The assertion is based on the difficulty of removing protons from negatively charged species, while the reason simply states the presence of a mixture of acids.

### Final Answer
Both the assertion and reason are true, but the reason is not the correct explanation for the assertion. Therefore, the correct choice is:
**Option B: Both assertion and reason are true, but reason is not the correct explanation of assertion.**