When an inorganic compound reacts with `SO_2` in aqueous medium produces `(A). (A)` on reaction with `Na_2 CO_3` gives the compound `(B)` which with sulphur gives a substance `(C)` used in photography. The compound `(C)` is.

Options

A. `Na_2 S_2 O_3`
B. `Na_2 SO_4`
C. `Na_2 S`
D. `Na_2 S_2 O_7`

Explanation

To solve the problem step by step, we will identify the compounds formed at each stage of the reaction as described in the question.

### Step 1: Identify the initial reaction
We start with an inorganic compound (let's call it X) that reacts with sulfur dioxide (SO₂) in an aqueous medium. The product of this reaction is compound A.

**Reaction:**
\[ X + SO_2 + H_2O \rightarrow A \]

### Step 2: Determine compound A
From the video transcript, we learn that when an inorganic compound reacts with SO₂ and water, it forms sodium bisulfite (NaHSO₃) as compound A.

**Compound A:**
\[ A = NaHSO_3 \]

### Step 3: Reaction of compound A with Na₂CO₃
Next, compound A (NaHSO₃) reacts with sodium carbonate (Na₂CO₃) to form compound B.

**Reaction:**
\[ NaHSO_3 + Na_2CO_3 \rightarrow B + H_2O + CO_2 \]

### Step 4: Determine compound B
From the reaction, we find that compound B is sodium sulfite (Na₂SO₃).

**Compound B:**
\[ B = Na_2SO_3 \]

### Step 5: Reaction of compound B with sulfur
Now, compound B (Na₂SO₃) reacts with sulfur (S) to form compound C.

**Reaction:**
\[ Na_2SO_3 + S \rightarrow C \]

### Step 6: Determine compound C
The product of this reaction is sodium thiosulfate (Na₂S₂O₃), which is a compound used in photography.

**Compound C:**
\[ C = Na_2S_2O_3 \]

### Final Answer
The compound C used in photography is sodium thiosulfate (Na₂S₂O₃).

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