Xenon trioxide `(XeO_(3))` forms xenate ion in alkaline medium.
`XeO_(3)+NaOH rarr Na[HXeO_(4)]`
But the xenate ions slowly disproportionate in alkaline solution as `Na[HXeO_(4)]+NaOH rarr Z+Xe+O_(2)+H_(2)O`
The compound Z is expexted to be

Options

A. `Na_(2)XeO_(3)`
B. `Na_(2)XeO_(4)`
C. `Na_(4)XeO_(6)`
D. `Na_(4)XeO_(4)`

Answer

To solve the problem, we need to analyze the reactions involving xenon trioxide `(XeO3)` and its behavior in alkaline medium.

### Step-by-Step Solution:

1. **Identify the Initial Reaction**:
The first reaction given is:
\[ XeO_3 + NaOH \rightarrow Na[HXeO_4] \]
Here, xenon trioxide reacts with sodium hydroxide to form the xenate ion, `Na[HXeO_4]`. In this reaction, xenon is in the +6 oxidation state.

**Hint**: Remember that xenon can exhibit multiple oxidation states, and in this case, it is +6 in the xenate ion.

2. **Disproportionation Reaction**:
The next part of the problem states that the xenate ion undergoes disproportionation in alkaline solution:
\[ Na[HXeO_4] + NaOH \rightarrow Z + Xe + O_2 + H_2O \]
Here, we need to identify the compound `Z`.

**Hint**: Disproportionation reactions typically involve a species being oxidized and reduced simultaneously.

3. **Determine the Oxidation States**:
In the xenate ion `Na[HXeO_4]`, xenon is in the +6 oxidation state. During the disproportionation, xenon can potentially be oxidized to a higher oxidation state. The maximum oxidation state of xenon is +8.

**Hint**: Consider the possible oxidation states of xenon and how they can change during the reaction.

4. **Formulate the Reaction**:
If xenon is oxidized to +8, we can represent the product `Z` as sodium perxenate, which has the formula `Na4[XeO6]`. This means that in the reaction:
\[ 2Na[HXeO_4] + 2NaOH \rightarrow Na4[XeO_6] + Xe + O_2 + 2H_2O \]

**Hint**: Balancing the reaction is crucial. Ensure that the number of atoms on both sides of the equation is equal.

5. **Final Identification of Compound Z**:
From the above formulation, we conclude that the compound `Z` is sodium perxenate, which can be written as:
\[ Z = Na_4[XeO_6] \]

**Hint**: When identifying compounds, always check the oxidation states and the overall charge balance.

### Conclusion:
The expected compound `Z` is sodium perxenate, represented as `Na4[XeO6]`.