Anionic Tests and Observations in Chemistry

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Questions and Answers

What observation occurs when a salt containing carbonate ions is treated with dilute HCl?

Formation of a precipitate

Color change to blue

Effervescence and CO2 evolution (correct)

Release of a brown gas

Which gas evolves during the experiment with SO3-2 that causes the solution to turn yellow due to precipitation of sulphide?

H2S

NO2

Cl2

SO2 (correct)

Which observation is characteristic of an acidic radical containing sulphide?

Clear solution with no gas evolved

Dense white fumes with ammonium hydroxide

Brown fumes evolution

Suffocating odour and blackness on lead acetate paper (correct)

When testing for nitrate ions (NO3-), which observation indicates their presence?

Faint blue color in the solution Signup and view all the answers

What conclusion can be drawn if no gas is evolved when a salt is treated with concentrated H2SO4?

The acidic radical may be from group II or III Signup and view all the answers

Which anionic test produces a white precipitate with barium chloride and is soluble in mineral acids?

Borate ion Signup and view all the answers

What color does the solution become when testing for bromide ions with concentrated H2SO4?

Reddish-brown Signup and view all the answers

Which compound forms when iodide ions react with concentrated H2SO4 and produces violet vapours?

Iodine (I2) Signup and view all the answers

When identifying chloride ions, which indicates the presence of HCl gas?

White clouds of ammonium chloride Signup and view all the answers

What is produced when nitrate ions are treated with concentrated H2SO4 and copper turnings are added?

Blue color solution Signup and view all the answers

Which test would confirm the presence of the bromide ion using silver nitrate?

Pale yellow precipitate Signup and view all the answers

Which of the following ions can form a white precipitate with lead acetate that is soluble in boiling water?

Bromide ion Signup and view all the answers

Which test involves observing the disappearance of pink color upon the addition of glycerol to verify a specific anion?

Borate ion Signup and view all the answers

What color change indicates the presence of nitrate ions in a reaction?

Solution turns faint blue Signup and view all the answers

When testing for sulfate ions, what indicates a positive result?

Solubility in mineral acids Signup and view all the answers

What is the expected precipitate when testing for barium ions using ammonium carbonate?

Barium carbonate Signup and view all the answers

Which of the following tests confirms the presence of phosphate ions?

Canary yellow precipitate with ammonium molybdate Signup and view all the answers

Which of the following confirms the presence of strontium ions through a precipitate?

Strontium carbonate Signup and view all the answers

In a flame test, what color does calcium ions produce?

Brick-red Signup and view all the answers

What is the significance of using copper turnings in copper nitrate tests?

To evolve brown fumes Signup and view all the answers

What is the result of adding ammonium oxalate to a solution containing calcium ions?

White ppt of calcium oxalate Signup and view all the answers

With respect to barium phosphate, which statement is true?

It forms a white precipitate with BaCl2 Signup and view all the answers

What color and type of gas indicates the presence of iodide ions in a reaction?

Violet vapors produced Signup and view all the answers

Which compound is formed when testing for potassium ions with sodium cobalt nitrite?

Yellow ppt of Potassium cobalt nitrite Signup and view all the answers

What does a white precipitate of Ag2SO4 signify in a confirmatory test for sulfate?

Presence of sulfates Signup and view all the answers

What gas is evolved when testing for ammonium ions using sodium hydroxide?

Ammonia Signup and view all the answers

What color does the flame turn when testing for potassium ions?

Violet Signup and view all the answers

Which ion is suspected if there are no gases evolved from group II upon testing?

Phosphate ions (PO4-3) Signup and view all the answers

How can one confirm the presence of strontium ions after filtering the precipitate?

By dissolving the precipitate in hydrochloric acid Signup and view all the answers

What is produced when sodium hydroxide is added to a magnesium salt solution?

White precipitate of Mg(OH)2 Signup and view all the answers

Which ion would produce a pale green precipitate when treated with ammonium hydroxide?

Chromic ion (Cr3+) Signup and view all the answers

What is the result of adding ammonium sulfide to a solution of aluminum nitrate?

Formation of gelatinous white precipitate Signup and view all the answers

Which reagent is used in testing for ferrous ions to yield a pale blue precipitate?

Potassium ferrocyanide Signup and view all the answers

Which of the following ions gives a brown precipitate upon reaction with ferric chloride?

Fe3+ Signup and view all the answers

When sodium doxide reacts with chromic ion, which solution results?

Yellow solution Signup and view all the answers

What type of precipitate is formed when lead cation is tested with dilute hydrochloric acid?

White precipitate of lead chloride Signup and view all the answers

Which of the following solutions produces a yellow precipitate when tested with potassium iodide for mercurous cation?

Solution of mercurous nitrate Signup and view all the answers

Which of the following best describes the precipitation of aluminum ions in the presence of ammonium hydroxide?

The formation of a white gelatinous precipitate Signup and view all the answers

Which of the following ions would not form a precipitate with sodium hydroxide?

Na+ Signup and view all the answers

The precipitation of which cation is confirmed by a scarlet red precipitate when combined with potassium chromate?

Silver cation Signup and view all the answers

Which characteristic indicates the presence of cations in group II when using H2S?

Precipitation as sulfides in acidic medium Signup and view all the answers

What is the outcome of adding dilute hydrochloric acid to a solution containing silver nitrate?

Formation of a white precipitate Signup and view all the answers

Which of the following describes the confirmatory test result for lead cation using potassium chromate?

Yellow precipitate of PbCrO4 Signup and view all the answers

What happens to the white precipitate formed from mercurous cation when ammonia is added?

It becomes black Signup and view all the answers

Which of the following is the group reagent used to precipitate Group I cations?

Dilute hydrochloric acid Signup and view all the answers

Study Notes

Acidic Radicals

Experiment: Salt + dilute HCl
Observation 1: Effervescence on cold, CO₂ gas evolved, which renders lime water turbid.
Result 1: CO₃^2- or HCO₃^-
Observation 2: SO₂ gas with suffocating odor on warming, turns acidified potassium dichromate paper to green, and solution is clear.
Result 2: SO₃^2-
Observation 3: SO₂ gas with suffocating odor on warming, turns acidified potassium dichromate paper green, and solution becomes yellow due to a precipitate.
Result 3: S₂O₃^2- (S + SO₃^2-)
Observation 4: H₂S gas evolves on warming, with a rotten egg odor, and blackens lead acetate paper.
Result 4: S^2-
Observation 5: NO₂ gas evolves with 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 (More Detailed Scheme)

Experiment: Salt + concentrated H₂SO₄
Observation 1: HCl - colorless gas evolves, forming dense white fumes when a rod dipped in ammonium hydroxide is brought near the test tube.
Result 1: Chloride (Cl^-)
Observation 2: HBr/Br₂ - reddish brown gases, solution turns reddish brown.
Result 2: Bromide (Br^-)
Observation 3: HF/I₂ - violet vapors, turning starch paper blue, layer of violet sublimate, with sulfur ppt on sides of tube.
Result 3: Iodide (I^-)
Observation 4: NO₂ - brown fumes, which become dense, reaction mixture heated with copper turnings, solution turns 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 (Salt solution + BaCl₂ solution)

Experiment: Salt solution + BaCl₂ solution
Observation 1: White ppt of insoluble in mineral acids (barium sulfate).
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 (Group III, SO₄^2-, PO₄^3-, B₄O₇^2-)

Sulfate ion test: Salt solution + barium chlorides, white ppt of barium sulfate, insoluble in mineral acids.
Phosphate ion test: Salt solution + barium chlorides, white ppt of barium phosphate, soluble in mineral acids.
Borate ion test: Salt solution + barium chlorides, white ppt of barium metaborate, soluble in mineral acids.

Acidic Radicals (More Tests)

Chloride: Salt solution + AgNO₃ = white ppt (AgCl), soluble in dilute ammonia.
Bromide: Salt solution + AgNO₃ = pale yellow ppt (AgBr), soluble in dilute nitric acid.
Iodide: Salt solution + AgNO₃= yellow ppt (AgI), soluble in ammonia solution.
Nitrate: Salt solution + NaOH + warming = brown fumes NO₂, solution turns pale blue.

Acidic Radicals (Group I—CO₃^2-, HCO₃^-, S^2-, SO₃^2-, S₂O₃^2-, NO₃^-)

Carbonate/Bicarbonate: Effervescence with HCl, gas turns lime water milky. (CaCO₃).
Sulfide: H₂S gas with rotten egg smell, blackens lead acetate.
Sulfite: SO₂ gas with suffocating odor, turns acidified potassium dichromate paper green.
Thiosulfate: SO₂ gas, turning acidified potassium dichromate paper green, and solution becomes yellow due to precipitate.
Nitrate: NO₂ gas evolves with brown fumes, solution turns faint blue.

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

Chloride: Solid + few drops concentrated H2SO4 and warm (HCl gas evolves)

Basic Radicals (Group V)

Barium Ion (Ba²⁺): Salt solution + potassium chromate (K₂CrO₄) = yellow ppt (BaCrO₄), dissolving in mineral acids. Salt solution + ammonium oxalate= white ppt (BaC₂O₄). Flame test: yellowish-green.

Basic Radicals (Group VI)

Ammonium Ion (NH₄⁺): Salt solution + sodium hydroxide = ammonia gas (NH₃) evolves-test with HCl—turns white fumes.
Potassium Ion (K⁺): Salt solution = sodium cobalt nitrite = yellow ppt (K₃[Co(NO₂)₆]). Flame Test= violet color.

Basic Radicals (Group IV)

Manganese Ion (Mn²⁺): Salt solution + NaOH = white ppt Mn(OH)₂. Salt solution + disodium hydrogen phosphate = white ppt MnHPO₄.
Nickel Ion (Ni²⁺): Salt solution + NaOH = green ppt Ni(OH)₂. Salt solution + NH₄OH + dimethylglyoxime = red ppt Ni(DMG)₂.
Cobalt Ion (Co²⁺): Salt solution + NaOH = blue ppt (Co(OH)₂), changes to pink when warmed with excess NaOH.
Zinc Ion (Zn²⁺): Salt solution + NaOH = white ppt Zn(OH)₂. Salt solution + potassium ferrocyanide K₄[Fe(CN)₆] = white ppt Zn₂ [Fe(CN)₆].

Basic Radicals (Group III)

Chromium Ion (Cr³⁺): Solution of chromic nitrate + buffer = pale green ppt Cr(OH)3
Aluminium Ion (Al³⁺): Solution of aluminum nitrate + buffer = gelatinous white ppt Al(OH)₃
Ferrous Ion (Fe²⁺): Solution of ferrous ammonium sulfate + buffer = pale green ppt. + K₄[Fe(CN)₆] = pale blue ppt
Ferric Ion (Fe³⁺): Solution of ferric chloride + buffer = brown ppt Fe(OH)₃ . + K₄[Fe(CN)₆] = dark blue ppt.

Basic Radicals (Group II—Pb, Hg₂, Ag)

Lead Ion (Pb²⁺): Lead nitrate + dilute HCl = white ppt (PbCl₂). Dissolves in hot water.
Mercurous Ion (Hg²⁺): Mercurous nitrate + dilute HCl = white ppt (Hg₂Cl₂). Becomes black in ammonia.
Silver Ion (Ag⁺): Silver nitrate + dilute HCl = white ppt (AgCl). + KI = yellow ppt (AgI). + K₂CrO₄ = scarlet red ppt (Ag₂CrO₄), soluble in nitric acid.

Group II, Subgroup A, B and Tests

Mercury (II): Mercuric Chloride + Hydrogen Sulphide, black precipitate.
Bismuth: Bismuth Nitrate + Hydrochloric Acid + Hydrogen Sulphside = Brown precipitate.
Cadmium: Cadmium Sulfate + Hydrochloric Acid + Hydrogen Sulphside = Yellow precipitate.
Copper: Copper Sulphate + Hydrochloric Acid + Hydrogen Sulphside = Black precipitate

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Description

This quiz covers various anionic tests and observations in chemistry, focusing on the reactions of different ions with acids and reagents. You will explore gaseous products, color changes, and precipitation reactions, as well as indicators for the presence of specific anions like nitrate, bromide, and chloride. Test your knowledge on these fundamental concepts in analytical chemistry!