Inorganic Chemistry

Aim.
To detect one acidic radical (anion) present in the sample "M3" using standard preliminary (dry) and confirmatory (wet) tests.

Apparatus & Reagents (as needed).
Test tubes, glass rod, dropper, corked test tube for brown–ring, watch glass, lead acetate paper, blue/red litmus, lime water (Ca(OH)2), freshly prepared FeSO4 solution, BaCl2 solution, dil. & conc. H2SO4, AgNO3, dil. NH3, chlorine water, starch–KI paper, KMnO4/acid, etc.

Step 1: Preliminary (physical) check.
Note colour/odour/texture. (Most anion tests are independent of this, but note any vinegar smell ⇒ acetate, rotten‐egg odour on moistening ⇒ sulphide hints.)

Step 2: Dry tests (on solid or with conc. acid).
(A) Action of dilute H2SO4 on a pinch of salt. Observe the gas.

(B) Action of conc. H2SO4 (cautiously).

Step 3: Wet (confirmatory) tests on aqueous extract.
Prepare an aqueous extract of "M3" (boil gently with distilled water, cool, filter). Perform appropriate tests guided by Step 2. Use at most one confirmatory set and record the matching result.

(i) Halides (Cl^-, Br^-, I^-) — AgNO3 test:
To 2 mL extract add dil. HNO3, then AgNO3. Note precipitate and its behaviour with NH3.

(ii) Sulphate (SO4^2-): Add dil. HCl then BaCl2. White heavy ppt. that is insoluble in acids ⇒ BaSO4 confirms SO4^2-.
(iii) Sulphite (SO3^2-): Acidify extract and add acidified KMnO4 (or dichromate). Decolourisation with smell of SO2 confirms SO3^2-. Also gives white ppt. with BaCl2 soluble in dil. HCl (BaSO3).
(iv) Carbonate (CO3^2-): Add dil. acid; pass gas through lime water ⇒ milky CaCO3 which clears on excess CO2 (due to Ca(HCO3)2) confirms CO3^2-.
(v) Nitrate (NO3^-) — Brown‐ring test:
To 2 mL extract add freshly prepared FeSO4, then carefully add conc. H2SO4 down the side to form two layers. A brown ring at the junction ⇒ NO3^-.
(vi) Nitrite (NO2^-): Acidify a portion and add freshly prepared starch–KI paper: blue colour (via I2) confirms NO2^-. Also, with dil. H2SO4 and Cu turnings ⇒ brown fumes of NO2.
(vii) Phosphate (PO4^3-): Acidify with HNO3, warm, then add ammonium molybdate and heat gently: canary yellow ppt. of ammonium phosphomolybdate confirms PO4^3-.
(viii) Acetate (CH3COO^-): Warm the solid/extract with conc. H2SO4 + ethanol: fruity odour of ethyl acetate; or heat with conc. H2SO4 alone: vinegar smell (acetic acid).

Step 4: Inference and Report.
Match your observations from Step 2 with confirmatory evidence from Step 3 and write:
Anion present in "M3": ______________________ (write the confirmed radical).