Consider the following statements `:`
`S_(1) :` A metal chloride on heating with an aqueous solution of `K_(2)Cr_(2)O_(7)` and concentral `H_(2)SO_(4)` produces deep red vapours.
`S_(2) :` Lead nitrate dissolved in water responds to brown ring test.
`S_(3) :` Deep red solution of ferric acetate on boiling with water turns to brownishred solution.
`S_(4) : NaNO_(2)` solution acidified with acetic acid produces blue colour with iodide solution and starch paste of these.

Options

A. `S_(1),S_(2)` and `S_(3)` are correct
B. `S_(1),S_(3)` and `S_(4)` are incorrect
C. Only `S_(3)` and `S_(4)` are in correct
D. All are incorrect

Explanation

To determine the correctness of the statements provided, we will analyze each statement one by one.

### Step 1: Analyze Statement S1
**Statement S1:** A metal chloride on heating with an aqueous solution of K₂Cr₂O₇ and concentrated H₂SO₄ produces deep red vapours.

- When a metal chloride (like sodium chloride) is heated with potassium dichromate (K₂Cr₂O₇) and concentrated sulfuric acid (H₂SO₄), chromyl chloride (CrO₂Cl₂) is produced. This compound is known to produce deep red vapours.
- Therefore, **Statement S1 is correct.**

### Step 2: Analyze Statement S2
**Statement S2:** Lead nitrate dissolved in water responds to the brown ring test.

- The brown ring test is used to detect nitrate ions (NO₃⁻). When lead nitrate (Pb(NO₃)₂) is dissolved in water, it dissociates into Pb²⁺ and NO₃⁻ ions.
- However, if we perform the brown ring test directly on lead nitrate, the formation of lead sulfate (PbSO₄) as a white precipitate can obscure the results. If the precipitate is removed, the filtrate can still give a positive result for the brown ring test.
- Thus, **Statement S2 is correct.**

### Step 3: Analyze Statement S3
**Statement S3:** Deep red solution of ferric acetate on boiling with water turns to a brownish-red solution.

- Ferric acetate [Fe(C₂H₃O₂)₃] in aqueous solution can undergo hydrolysis. Upon boiling, it can form ferric hydroxide (Fe(OH)₃), which is a brown precipitate, along with acetic acid.
- Therefore, the deep red solution does indeed turn into a brownish-red solution due to the formation of ferric hydroxide.
- Hence, **Statement S3 is correct.**

### Step 4: Analyze Statement S4
**Statement S4:** NaNO₂ solution acidified with acetic acid produces blue colour with iodide solution and starch paste.

- When sodium nitrite (NaNO₂) is acidified with acetic acid and iodide ions are added, the reaction produces iodine (I₂) and other products. The blue color is typically observed when iodine reacts with starch, forming a blue complex.
- However, in this case, the reaction does not produce a blue color because the iodine is not present in sufficient quantity to react with starch, and the nitrite does not directly produce a blue color.
- Therefore, **Statement S4 is incorrect.**

### Conclusion
- **Correct Statements:** S1, S2, S3
- **Incorrect Statement:** S4

### Final Answer
The correct statements are S1, S2, and S3.

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