Acidic Radicals Experiment
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Questions and Answers

What is the observation when mixing barium chloride (BaCl2) with a solution containing sulfate ions (SO4–2)?

  • A yellow precipitate forms.
  • A white precipitate of barium sulfate forms. (correct)
  • A red solution is formed.
  • No precipitation occurs.

    • Which reaction produces a white precipitate that is soluble in mineral acids?

  • Salt solution + BaCl2 with PO4-3 (correct)
  • Salt solution + FeCl3 with PO4-3
  • Salt solution + BaCl2 with SO4-2 (correct)
  • Salt solution + AgNO3 with SO4-2

    • What occurs when NO2 is produced in a reaction mixture during a test for nitrate ions?

  • A white precipitate forms.
  • A brown solid forms.
  • The mixture turns blue. (correct)
  • No change occurs.

    • What color is the vapor produced when mixing HF with I2?

    <p>Violet vapor</p> Signup and view all the answers

    Which of the following methods would confirm the presence of phosphate ions (PO4–3)?

    <p>Using FeCl3 to create a yellow precipitate</p> Signup and view all the answers

    When heating a mixture that includes copper turnings and nitrate, which observation is expected?

    <p>Brown fumes evolve and the solution turns faint blue.</p> Signup and view all the answers

    If no gas is evolved during the testing for acidic radicals, what can be inferred?

    <p>The acidic radical may be from Group III.</p> Signup and view all the answers

    What is the result of adding sodium hydroxide to a solution containing manganous ions?

    <p>A white precipitate of Mn(OH)2</p> Signup and view all the answers

    Which ion produces a black precipitate when treated with hydrogen sulfide in the presence of ammonium chloride and hydroxide?

    <p>Nickel ion</p> Signup and view all the answers

    What happens to the cobalt hydroxide precipitate when warmed with excess sodium hydroxide?

    <p>It changes to pink</p> Signup and view all the answers

    Which confirmatory test results in a red precipitate?

    <p>Dimethylglyoxime test for nickel</p> Signup and view all the answers

    Which statement about zinc testing is false?

    <p>Zinc ions are detected by the formation of a green precipitate.</p> Signup and view all the answers

    What indicates the presence of carbonate ion when dil.HCl is added to a solid salt?

    <p>Effervescence with evolution of CO2 gas</p> Signup and view all the answers

    What is produced when sodium carbonate reacts with hydrochloric acid?

    <p>NaCl and CO2</p> Signup and view all the answers

    What color indicates a positive test for sulphide ion using lead acetate paper?

    <p>Black</p> Signup and view all the answers

    What is the result of treating sulphite ions with warm dilute HCl?

    <p>Evolution of SO2 gas with a suffocating smell</p> Signup and view all the answers

    Which of the following tests would confirm the presence of bicarbonate ions?

    <p>Salt solution + BaCl2 forms a white ppt</p> Signup and view all the answers

    What is the confirmatory test for sulphite ion using barium chloride?

    <p>Formation of white precipitate of barium sulphite</p> Signup and view all the answers

    Which gas is evolved when sulfide ions react with warm dilute HCl?

    <p>Hydrogen sulfide (H2S)</p> Signup and view all the answers

    What is formed when sodium sulfite and hydrochloric acid react?

    <p>SO2 and NaCl</p> Signup and view all the answers

    What color change occurs in potassium dichromate paper when exposed to sulfur dioxide gas?

    <p>Turn green</p> Signup and view all the answers

    What gas is evolved when thiosulphate ion is treated with warm dilute hydrochloric acid?

    <p>SO2</p> Signup and view all the answers

    What color does potassium dichromate paper turn when exposed to the gas evolved from thiosulphate ion treatment?

    <p>Green</p> Signup and view all the answers

    What precipitate is formed when thiosulphate ion is mixed with barium chloride solution?

    <p>Barium thiosulphate</p> Signup and view all the answers

    Which of the following indicates the presence of nitrite ions in a solution?

    <p>Formation of white precipitate with AgNO3</p> Signup and view all the answers

    What happens to the solution when a solid nitrite is warmed with dilute hydrochloric acid?

    <p>The solution becomes pale blue</p> Signup and view all the answers

    What is the resultant gas formed when nitrous acid decomposes?

    <p>NO2</p> Signup and view all the answers

    Which of the following is NOT a confirmatory test for nitrite ions?

    <p>Barium chloride test</p> Signup and view all the answers

    What color is the precipitate formed during the formation of lead thiosulphate?

    <p>White</p> Signup and view all the answers

    What is observed when ferric chloride solution is added to thiosulphate ion?

    <p>Dark violet coloration disappears</p> Signup and view all the answers

    What is produced when sodium thiosulphate is treated with dilute hydrochloric acid?

    <p>NaCl, S, and SO2</p> Signup and view all the answers

    What is the result of adding disodium hydrogen phosphate to a magnesium salt solution with NH4Cl?

    <p>Formation of white precipitate</p> Signup and view all the answers

    Which color is produced during the flame test for sodium ions?

    <p>Golden yellow</p> Signup and view all the answers

    What is the precipitate formed when chromic ion Cr3+ reacts with a buffer solution?

    <p>Pale green precipitate</p> Signup and view all the answers

    Which compound is indicated by the formation of a dark blue precipitate when ferrous ions react with potassium ferricyanide?

    <p>Fe3[Fe(CN)6]2</p> Signup and view all the answers

    What happens when aluminium ions Al3+ react with ammonium sulfate?

    <p>Formation of a white precipitate</p> Signup and view all the answers

    What is the outcome when ferric ion Fe3+ is treated with NaOH?

    <p>Brown precipitate</p> Signup and view all the answers

    In the presence of sodium peroxide, which color solution is obtained from chromic ions?

    <p>Yellow solution</p> Signup and view all the answers

    What is the identity of the precipitate formed when ferrous ammonium sulfate reacts with a buffer solution?

    <p>Green precipitate</p> Signup and view all the answers

    What distinguishes aluminium hydroxide from aluminium sulphide in reactions with ammonium sulphate?

    <p>Aluminium sulphide forms a gas</p> Signup and view all the answers

    Which precipitation form occurs for group III cations consisting of chromic, aluminium, ferrous, and ferric ions?

    <p>As hydroxide precipitates</p> Signup and view all the answers

    Study Notes

    Acidic Radicals Scheme

    • Experiment: Salt + dilute HCl
    • Observation 1: Effervescence on cold, CO₂ gas evolved, which renders limewater turbid
    • Result 1: CO₃⁻² or HCO₃⁻
    • Observation 2: SO₂ gas suffocating odour on warming, turns acidified potassium dichromate paper to green and solution clear
    • Result 2: SO₃⁻²
    • Observation 3: SO₂ gas suffocating odour on warming, turns acidified potassium dichromate paper to green and solution becomes yellow due to sulphide precipitation
    • Result 3: S₂O₃⁻² (S + SO₃⁻²)
    • Observation 4: H₂S gas evolves on warming, has odour like rotten eggs, and blackens lead acetate paper
    • Result 4: S⁻²
    • Observation 5: NO₂ gas evolves, brown fumes, and solution turns faint blue
    • Result 5: NO₃⁻
    • Observation 6: No gas evolved
    • Result 6: Acidic radical is not from group I; it may be from group II or group III

    Acidic Radicals Scheme (cont.)

    • Experiment: Salt + concentrated H₂SO₄
    • Observation 1: HCl: colourless gas evolves which gives dense white fumes when a rod dipped in ammonium hydroxide is brought near the mouth of the test tube
    • Result 1: Chloride (Cl⁻)
    • Observation 2: Mix of HBr and Br₂: reddish-brown gases, solution turns reddish brown
    • Result 2: Bromide (Br⁻)
    • Observation 3: Mix of HF and I₂: violet vapours, which turn starch paper blue and a layer of violet sublimate is formed on the sides of the tube (sulphur ppt on walls of tube)
    • Result 3: Iodide (I⁻)
    • Observation 4: NO₂: Brown fumes evolve which become dense upon heating the reaction mixture after addition of copper turnings and the solution becomes faint blue
    • Result 4: Nitrate (NO₃⁻)
    • Observation 5: No gas evolved
    • Result 5: Acidic radical is not from group II; it may be from group III

    Acidic Radicals Scheme (cont.)

    • Experiment: Salt solution + BaCl₂ solution
    • Observation 1: White ppt of insoluble in mineral acids (barium sulphate)
    • Result 1: SO₄⁻²
    • Observation 2: White ppt of soluble in mineral acids (barium phosphate or barium metaborate)
    • Result 2: PO₄⁻³ or B₄O₇⁻²

    Acidic Radicals (SO₄⁻², PO₄⁻³, B₄O₇⁻²) Group III

    • Test 1: Sulphate ions [SO₄⁻²] -Procedure: Salt solution + Barium chlorides (BaCl₂): White ppt of barium sulphate, insoluble in mineral acids -Confirmation tests: Concentrated Salt solution + AgNO₃: White ppt (Ag₂SO₄) -Procedure: Salt solution + lead acetate: White ppt soluble in ammonium acetate - NaOH

    • Test 2: Phosphate ions [PO₄⁻³] -Procedure: Salt solution + Barium chlorides (BaCl₂): White ppt of barium phosphate, soluble in mineral acids -Confirmation tests: Salt solution + AgNO₃: Yellow ppt soluble in NH₄OH -Procedure: Salt solution + FeCl₃: Yellow ppt (FePO₄) soluble in mineral acids -Procedure: Salt solution + excess of ammonium molybdate + conc HNO₃ and heat: Canary yellow ppt

    • Test 3: Borate ions [B₄O₇⁻²] -Procedure: Salt solution + Barium chlorides (BaCl₂): White ppt of (Ba(BO₂)₂), soluble in mineral acids

    Acidic Radicals (Cl⁻, Br⁻, I⁻, NO₃⁻) Group II

    • Test 1: Chloride anion [Cl⁻] -Procedure: Solid + a few drops of concentrated H₂SO₄ and warm: HCl evolves, recognized by formation of white clouds of ammonium chloride when a glass rod wetted with ammonia solution is held near the tube's mouth -Confirmation test: Salt solution + AgNO₃: White ppt (AgCl) soluble in dilute ammonia solution -Procedure: Concentrated salt solution + lead acetate: White ppt of lead chloride soluble in hot water

    • Test 2: Bromide anion [Br⁻] -Procedure: Solid + concentrated H₂SO₄ and warm: Reddish-brown vapours of Br₂ + HBr are evolved, the solution becomes reddish-brown

    • Confirmation Tests: Salt solution + AgNO₃: Pale yellow ppt soluble in dilute HNO₃ -Procedure: Salt solution + lead acetate: White ppt soluble in boiling water

    • Test 3: Iodide anion [I⁻] -Procedure: Solid + concentrated H₂SO₄ and warm: Violet vapours (I₂) are evolved, which turn starch paper blue

    • Confirmation Tests: Salt solution + AgNO₃: Yellow ppt soluble in ammonia solution

    • Procedure: Salt solution + HgCl₂: Scarlet red ppt of mercuric iodide, soluble in excess KI

    • Test 4: Nitrate anion [NO₃⁻] -Procedure: Solid + concentrated H₂SO₄ and heat: Brown fumes of NO₂ evolve, become dense upon heating the reaction mixture after addition of copper turnings, and the solution acquires blue colour

    • Confirmation Tests: Salt solution + AgNO₃: Pale yellow ppt

    • Procedure: Salt solution + FeSO₄ + conc H₂SO₄: Brown ring

    Acidic Radicals (CO₃⁻², HCO₃⁻, S⁻², SO₃⁻², S₂O₃⁻², NO₃⁻) Group I

    • Test 1: Carbonate and Bicarbonate -Procedure: If effervescence occurs with evolution of colourless, odourless gas upon adding dilute HCl to solid salt, carbonate or bicarbonate ion is present.

    • Procedure: The gas turns lime water milky due to the formation of calcium carbonate. (Na₂CO₃ + HCl→NaCl + H₂O + CO₂) (Ca(OH)₂) + CO₂→CaCO₃ + H₂O Confirmatory Tests (CO₃⁻²): ----Salt solution+ MgSO₄: White ppt (MgCO₃) ----Salt solution + HgCl₂: Reddish brown ppt (HgCO₃-3HgO) if no ppt on cold. ----Salt solution + BaCl₂: White ppt (BaCO₃) ----Salt solution + AgNO₃: White ppt (Ag₂CO₃)

    • Test 2: Sulphide ion [S⁻²]

    • Confirmatory Tests: (S⁻²) Salt solution + Sodium Nitroprusside : Purple/Black ppt is formed, (S⁻²) Salt solution + Lead Acetate : Black ppt of lead sulphide (PbS),

    • Test 3: Sulphite ion [SO₃⁻²]

      • Procedure: Sulphite treated with warm dilute HCl, SO₂ gas is given off with smell of burning sulfur. This gas turns acidified potassium dichromate paper green and the solution becomes clear. K₂Cr₂O₇ + H₂SO₄ + 3SO₂ → K₂SO₄ + Cr₂(SO₄)₃ + H₂O

    • Test 4: Thiosulphate ion [S₂O₃⁻²]

      • On treating thiosulphate with warm dilute HCl, SO₂ gas is evolved with suffocating smell of burning sulfur. The gas turns potassium dichromate paper acidified with dil H₂SO₄ to green and the solution becomes clear.

    • Test 5: Nitrite ion [NO₂⁻]

      • On treating a solid nitrite with dilute HCl and warming, reddish brown fumes of NO₂ gas are evolved and the solution becomes pale blue.

    Basic Radicals (Ba²⁺, Sr²⁺, Ca²⁺) Group V

    • Test 1: Barium Ion [Ba²⁺]

      • Procedure: Salt solution + (NH₄Cl) + (NH₄OH) + (NH₄)₂CO₃: White ppt of barium carbonate (BaCO₃)
      • Confirmation Tests: -Salt solution + Potassium chromate (K₂CrO₄) : Yellow ppt of barium chromate (BaCrO₄) soluble in mineral acids -5 drops of salt solution + 4 drops of Ammonium oxalate solution: White ppt of barium oxalate (BaC₂O₄)

    • Test 2: Strontium Ion [Sr²⁺]

      • Procedure: Salt solution + (NH₄Cl) + (NH₄OH) + (NH₄)₂CO₃: White ppt of strontium carbonate (SrCO₃)
      • Confirmation Tests: 6 drops of salt solution + 6 drops of Ammonium oxalate solution: White ppt of strontium oxalate (SrC₂O₄)

    • Test 3: Calcium Ion [Ca²⁺]

      • Procedure: Salt solution + (NH₄Cl) + (NH₄OH) + (NH₄)₂CO₃: White ppt of calcium carbonate (CaCO₃)

    Basic Radicals (NH₄⁺, K⁺, Mg²⁺, Na⁺) Group VI

    • Test 1: Ammonium Ion [NH₄⁺]

      • Procedure: Salt solution + NaOH, solid and solution boiled: NH₃ gas evolved, and exposed to glass rod wetted with HCl, forming white fumes

    • Procedure: Salt solution + Sodium cobalt nitrite (Na₃[Co(NO₂)₆]): Yellow ppt of ammonium cobalt nitrite (NH₄)₃[Co(NO₂)₆]

    • Test 2: Potassium Ion [K⁺]

      • Procedure: Salt solution + Sodium cobalt nitrite (Na₃[Co(NO₂)₆]): Yellow ppt of potassium cobalt nitrite (K₃[Co(NO₂)₆]).

    • Procedure: Flame test: Salt colors the flame violet

    • Test 3: Magnesium Ion [Mg²⁺]

      • Procedure: Salt solution + NH₄Cl + NH₄OH + Na₂HPO₄: White ppt of magnesium ammonium phosphate (MgNH₄PO₄)
      • Procedure: Salt solution + NaOH: White ppt of magnesium hydroxide (Mg(OH)₂)

    • Test 4: Sodium Ion [Na⁺]

      • Procedure: Flame test: Salt colors the flame golden yellow.

    Basic Radicals (Cr³⁺, Al³⁺, Fe²⁺, Fe³⁺) Group III

    • Test 1: Chromic Ion [Cr³⁺] -Procedure: Soln of chromic nitrate + buffer: Pale green ppt Cr(OH)₃

    • Test 2: Aluminium Ion [Al³⁺]

      • Procedure: Soln of aluminium nitrate + buffer: Gelatinous white ppt Al(OH)₃

    • Test 3: Ferrous Ion [Fe²⁺]

    • Procedure: Soln of ferrous ammonium sulphate + buffer soln: Green ppt Fe(OH)₂

    • Test 4: Ferric Ion [Fe³⁺]

    • Procedure: Soln of Ferric Chloride + buffer soln: Brown ppt Fe(OH)₃.

    Basic Radicals (Mn²⁺, Ni²⁺, Co²⁺, Zn²⁺) Group IV

    • Test 1: Manganous Ion [Mn²⁺]

    • Procedure: Salt solution + NH₄Cl + NH₄OH + H₂S: Buff ppt of manganese sulfide (MnS)

    • Confirmatory Tests: Salt solution + NaOH: White ppt of manganous hydroxide (Mn(OH)₂), insoluble in excess reagent . Salt solution + Na₂HPO₄: White ppt of Manganese(II) Hydrogen Phosphate (MnHPO₄)

    • Test 2: Nickel Ion [Ni²⁺] -Procedure: Salt solution + NH₄Cl + NH₄OH + H₂S: Black ppt of nickel sulphide (NiS) insoluble in mineral acid and soluble in aqua regia

    • Confirmatory Tests: Salt solution + NaOH: Green ppt of nickel hydroxide (Ni(OH₂) insoluble in excess of the reagent. Salt solution + NH₄OH + Dimethylglyoxime: Red ppt of Nickel dimethylglyoxime (Ni(DMG)₂)

    • Test 3: Cobalt Ion [Co²⁺]

    • Procedure: Salt solution + NH₄Cl + NH₄OH + H₂S: Black ppt of cobalt sulfide (CoS) insoluble in mineral acid and soluble in aqua regia

    • Confirmatory Tests: Salt solution + NaOH: Blue ppt changes to pink Co(OH)₂ on warming with excess of NaOH. Salt solution + Ammonium thiocyanate + drop of alcohol: Blue solution due to the formation of a complex salt of ammonium cobalt thiocyanate [(NH₄)₂Co(CNS)₄]

    • Test 4: Zinc Ion [Zn²⁺]

    • Procedure: Salt solution + NH₄Cl + NH₄OH + H₂S: White ppt of zinc sulphide (ZnS)

    • Confirmatory Tests: Salt solution + NaOH: White ppt of zinc hydroxide (Zn(OH)₂) soluble in excess of the reagent Salt solution + Potassium ferrocyanide (K₄[Fe(CN)₆]): White ppt of zinc ferrocyanide (Zn₂[Fe(CN)₆])

    Basic Radicals (Pb²⁺, Ag⁺, Hg₂²⁺) Group I

    • Test 1: Lead Cation [Pb²⁺]

    • Procedure: Soln of lead nitrate + dilute HCl: White ppt of lead chloride (PbCl₂), soluble in hot water.

    • Confirmatory Tests: Soln + KI: Yellow ppt (PbI₂), soluble in hot water giving golden crystals, and Soln+K₂CrO₄: Yellow ppt (PbCrO₄) soluble in alkali hydroxides and nitric acid but insoluble in acetic acid.

    • Test 2: Mercurous Cation [Hg₂²⁺]

      • Procedure: Soln of mercurous nitrate + dilute HCl: White ppt of (Hg₂Cl₂), insoluble in hot water
      • Confirmatory Tests: Soln+ KI: Yellow ppt (Hg₂I₂), soluble in excess of KI, forming complex K₂[HgI₄] Soln+ K₂CrO₄: Brown ppt of Hg₂CrO₄ in cold

    • Test Silver Cation [Ag⁺]:

      • Procedure: Soln of Silver nitrate + dilute HCl: White ppt (AgCl)
      • Confirmatory Tests: -Soln + KI: Yellow ppt (AgI) -Soln +K₂CrO₄: Scarlet red ppt (Ag₂CrO₄) soluble in dilute nitric acid.

    Group II-B

    • Test 1: Stannous ions [Sn²⁺] -Procedure: Soln stannous chloride + dil HCl +H₂S: Brown ppt SnS, Soln + NaOH: White ppt Sn(OH₂) , Soln+HgCl₂: White ppt

    • Test 2: Stannic ion [Sn⁴⁺]

    • Procedure: Soln of stannic chloride + dil HCl +H₂S: yellow ppt, Soln +NaOH: White gelatinous Sn(OH)₄ soluble in excess of NaOH, Soln+HgCl₂: NO Preciptate

    • Test 3: Antimonious ion [Sb³⁺]

    • Procedure: Soln of antimony trichloride + dil HCl + H₂S: Orange ppt Sb₂Sз -Procedure: Soln +NaOH: White ppt

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