`[X]+H_(2)SO_(4) rarr [Y]` a colourless gas with irritating smell `[Y] + K_(2)Cr_(2)O_(7) + H_(2)SO_(4) rarr` green solution `[X]` and `[Y]` are

Options

A. `SO_(3)^(2-), SO_(2)`
B. `Cl^(-), HCl`
C. `S^(2-), H_(2)S`
D. `CO_(3)^(2-), CO_(2)`

Answer

To solve the problem step by step, we need to identify the substances X and Y based on the given reactions.

### Step 1: Identify the first reaction
The first part of the question states:
\[ [X] + H_2SO_4 \rightarrow [Y] \]
We need to find a substance [X] that reacts with sulfuric acid (H₂SO₄) to produce a colorless gas with an irritating smell, [Y].

### Step 2: Determine the identity of [Y]
A common colorless gas with an irritating smell produced from the reaction of a sulfite with sulfuric acid is sulfur dioxide (SO₂). Therefore, we can propose that:
\[ [Y] = SO_2 \]

### Step 3: Identify [X]
Since we established that [Y] is SO₂, we need to find [X]. The sulfite ion (SO₃²⁻) reacts with sulfuric acid to produce sulfur dioxide:
\[ SO_3^{2-} + H_2SO_4 \rightarrow SO_2 + H_2O \]
Thus, we can conclude that:
\[ [X] = SO_3^{2-} \]

### Step 4: Identify the second reaction
The second part of the question states:
\[ [Y] + K_2Cr_2O_7 + H_2SO_4 \rightarrow \text{green solution} \]
We know [Y] is SO₂, and when sulfur dioxide reacts with potassium dichromate (K₂Cr₂O₇) in the presence of sulfuric acid, it reduces the dichromate ion, resulting in a green solution of chromium(III) sulfate (Cr₂(SO₄)₃).

### Step 5: Write the complete reaction
The complete reaction can be written as:
\[ SO_2 + K_2Cr_2O_7 + H_2SO_4 \rightarrow Cr_2(SO_4)_3 + K_2SO_4 + H_2O \]
The chromium(III) sulfate (Cr₂(SO₄)₃) is responsible for the green color.

### Conclusion
From the above steps, we conclude:
- \( [X] = SO_3^{2-} \)
- \( [Y] = SO_2 \)

### Summary of the Solution
- \( [X] \) is the sulfite ion \( SO_3^{2-} \).
- \( [Y] \) is sulfur dioxide \( SO_2 \).

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