`Na_(2)SO_(3),Na_(2)S_(2)O_(3),Na_(2)CO_(3),Na_(2)CrO_(4)` are separately treated with `AgNO_(3)` solution in how many cases is/are red ppt abtained ?

Explanation

To determine how many cases result in a red precipitate when the compounds `Na2SO3`, `Na2S2O3`, `Na2CO3`, and `Na2CrO4` are treated with `AgNO3`, we will analyze each compound's reaction with silver nitrate step by step.

### Step 1: Reaction of Sodium Sulfite (Na2SO3) with AgNO3
- **Reaction**:
\[ Na_2SO_3 + 2AgNO_3 \rightarrow Ag_2SO_3 + 2NaNO_3 \]
- **Observation**: The product `Ag2SO3` is a white precipitate.

### Step 2: Reaction of Sodium Thiosulfate (Na2S2O3) with AgNO3
- **Reaction**:
\[ Na_2S_2O_3 + 2AgNO_3 \rightarrow 2Ag_2S_2O_3 + 2NaNO_3 \]
- **Observation**: The product `Ag2S2O3` is also a white precipitate.

### Step 3: Reaction of Sodium Carbonate (Na2CO3) with AgNO3
- **Reaction**:
\[ Na_2CO_3 + 2AgNO_3 \rightarrow Ag_2CO_3 + 2NaNO_3 \]
- **Observation**: The product `Ag2CO3` is a white precipitate.

### Step 4: Reaction of Sodium Chromate (Na2CrO4) with AgNO3
- **Reaction**:
\[ Na_2CrO_4 + 2AgNO_3 \rightarrow Ag_2CrO_4 + 2NaNO_3 \]
- **Observation**: The product `Ag2CrO4` is a red-brown precipitate.

### Conclusion
After analyzing all four reactions:
- Sodium Sulfite (Na2SO3): White precipitate
- Sodium Thiosulfate (Na2S2O3): White precipitate
- Sodium Carbonate (Na2CO3): White precipitate
- Sodium Chromate (Na2CrO4): Red-brown precipitate

Thus, a red precipitate is obtained **only in the case of sodium chromate (Na2CrO4)**.

### Final Answer
**1 case** results in a red precipitate.

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