`(X)overset(Ba^(2+))tounderset(("white ppt"))(Y)darroverset(Cl_(2)//H_(2)O)tounderset("White ppt")(Z)darr`
If the precipitate `(Zdarr)` is `BaSO_(4)`, which of the following can be (X)?

Options

A. `Na_(2)SO_(4)`
B. `Na_(2)SO_(3)`
C. `NaHSO_(4)`
D. `Na_(2)CO_(3)`

Explanation

To solve the question step by step, we need to analyze the reactions involved and identify the possible compound (X) that can lead to the formation of barium sulfate (BaSO₄) as the final precipitate (Z).

### Step 1: Understand the Final Precipitate
We know that the final precipitate (Z) is barium sulfate (BaSO₄). This indicates that we need a source of barium ions (Ba²⁺) and sulfate ions (SO₄²⁻) in the reaction.

### Step 2: Identify the Precursor Reaction
The question indicates that there is a white precipitate (Y) formed before reaching the final precipitate (Z). We need to determine what compound (X) can react to form this intermediate precipitate (Y) that eventually leads to BaSO₄.

### Step 3: Analyze the Reaction with Cl₂ and H₂O
The intermediate precipitate (Y) is formed when X reacts with Ba²⁺. The next step involves Y reacting with Cl₂ and H₂O to produce the final precipitate (Z), which is BaSO₄.

### Step 4: Determine Possible Compounds for X
To produce BaSO₄, we need to consider what compounds can react with Ba²⁺ to form a sulfide or sulfate.

- **Sodium sulfide (Na₂S)** can react with Ba²⁺ to form barium sulfide (BaS), which can then react with Cl₂ and H₂O to form BaSO₄.
- **Sodium thiosulfate (Na₂S₂O₃)** can also be considered, but it does not lead to the formation of BaSO₄ directly.
- **Sodium sulfate (Na₂SO₄)** would not be a suitable candidate as it already contains sulfate.

### Step 5: Conclusion
Based on the above analysis, the most likely candidate for (X) is sodium sulfide (Na₂S). This compound reacts with Ba²⁺ to form BaS, which can then react with Cl₂ and H₂O to yield BaSO₄.

### Final Answer
Thus, the correct option for (X) is sodium sulfide (Na₂S), which corresponds to option B.

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