Qualitative Inorganic Analysis: Detection of Acidic and Basic Radicals

Comprehensive vocabulary flashcards detailing the classification schemes, group reagents, characteristic reactions, and confirmatory tests for acidic and basic radicals in inorganic qualitative analysis.

Basic Radical

The positively charged cation of an inorganic salt derived from a base during neutralization (for example, $Cu^{2+}$ derived from $Cu(OH)_2$).

Acidic Radical

The negatively charged anion of an inorganic salt derived from an acid during neutralization (for example, $SO_4^{2-}$ derived from $H_2SO_4$).

Group I Acidic Radicals

The category of anions detected by treatment with dilute $H_2SO_4$ or dilute $HCl$, comprising carbonate ($CO_3^{2-}$), sulphite ($SO_3^{2-}$), sulphide ($S^{2-}$), nitrite ($NO_2^-$), and acetate ($CH_3COO^-$).

Group II Acidic Radicals

The category of anions detected by treatment with concentrated $H_2SO_4$, comprising chloride ($Cl^-$), bromide ($Br^-$), iodide ($I^-$), nitrate ($NO_3^-$), and oxalate.

Group III Acidic Radicals

Anions that do not evolve characteristic gases upon treatment with dilute or concentrated $H_2SO_4$, comprising sulphate ($SO_4^{2-}$), phosphate ($PO_4^{3-}$), borate, and fluoride.

Lime Water Confirmation for Carbonate

A test where evolved colourless $CO_2$ gas turns lime water milky due to $CaCO_3$ precipitation ($Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O$), and becomes colourless in excess $CO_2$ by forming soluble calcium bicarbonate ($Ca(HCO_3)_2$).

Acidified Dichromate Test for Sulphite

A confirmatory test in which evolved $SO_2$ gas turns filter paper moistened with acidified potassium dichromate green via the formation of chromic sulphate ($K_2Cr_2O_7 + H_2SO_4 + 3SO_2 \rightarrow K_2SO_4 + Cr_2(SO_4)_3 + H_2O$).

Lead Acetate Test for Sulphide

A test where $H_2S$ gas with a rotten egg odour turns lead acetate paper black through the precipitation of lead sulphide ($Pb(CH_3COO)_2 + H_2S \rightarrow PbS + 2CH_3COOH$).

Brown Complex Salt for Nitrite

The coordination complex $[Fe(H_2O)_5NO]SO_4 \cdot 2H_2O$ formed when nitric oxide ($NO$) evolved from nitrite is passed into dilute ferrous sulphate solution.

Neutral Ferric Chloride Test for Acetate

A test where adding neutral $FeCl_3$ solution to an aqueous acetate solution produces a blood-red coloration due to the formation of ferric acetate ($(CH_3COO)_3Fe$).

Ammonium Hydroxide Chloride Test

A reaction where pungent $HCl$ gas evolved from heating a solid chloride with concentrated $H_2SO_4$ reacts with $NH_4OH$ to produce dense white fumes of ammonium chloride ($NH_4Cl$).

Chromyl Chloride Test

A confirmatory test where a solid chloride heated with concentrated $H_2SO_4$ and $K_2Cr_2O_7$ evolves deep red vapours of $CrO_2Cl_2$, which dissolve in $NaOH$ to form yellow $Na_2CrO_4$, yielding a yellow precipitate of $PbCrO_4$ upon reaction with lead acetate.

Layer Test for Bromide

A test in which treating a bromide with dilute $H_2SO_4$, chlorine water, and $CHCl_3$ or $CCl_4$ liberates $Br_2$, colouring the organic layer brown ($2KBr + Cl_2 \rightarrow 2KCl + Br_2$).

Bromine Monochloride Formation

The reaction occurring when excess chlorine water is added during the bromide layer test, turning the layer pale yellow via $Br_2 + Cl_2 \rightarrow 2BrCl$ or colourless via hypobromous acid ($HBrO$) formation.

Layer Test for Iodide

A confirmatory test where iodide treated with dilute $H_2SO_4$, chlorine water, and $CHCl_3$ or $CCl_4$ yields free iodine ($I_2$), which dissolves to impart a violet colour to the organic layer.

Brown Ring Test for Nitrate

A confirmatory test in which nitrate treated with freshly prepared ferrous sulphate and concentrated $H_2SO_4$ forms a brown coordination ring ($[Fe(H_2O)_5NO]SO_4$) at the junction of the two liquids.

Barium Chloride Test for Sulphate

A test where soluble sulphate reacts with $BaCl_2$ to yield a white precipitate of barium sulphate ($BaSO_4$) that is completely insoluble in concentrated $HNO_3$.

Group I Basic Radicals

The cations $Pb^{2+}$, $Ag^+$, and $Hg_2^{2+}$ that precipitate as insoluble white chlorides ($PbCl_2$, $AgCl$, $Hg_2Cl_2$) upon addition of the group reagent, dilute $HCl$.

Lead Chloride Solubility Characteristic

The property of $PbCl_2$ precipitate dissolving in boiling water and recrystallizing into white crystalline needles upon cooling under tap water.

Group II Basic Radicals

Cations precipitated as sulphides by passing $H_2S$ gas in the presence of dilute $HCl$, divided into Group IIA ($Hg^{2+}, Pb^{2+}, Bi^{3+}, Cu^{2+}, Cd^{2+}$) and Group IIB ($As^{3+}, Sb^{3+}, Sn^{2+}, Sn^{4+}$).

Yellow Ammonium Sulphide Separation

A procedure used to separate Group II sulphides, where Group IIA sulphides remain insoluble and Group IIB sulphides dissolve at warm temperatures up to $60^\circ\text{C}$.

Group III Basic Radicals

The cations $Fe^{3+}$, $Al^{3+}$, and $Cr^{3+}$ which are precipitated as insoluble hydroxides ($Fe(OH)_3$, $Al(OH)_3$, $Cr(OH)_3$) by adding $NH_4OH$ in the presence of solid $NH_4Cl$.

Prussian Blue Test for Iron(III)

A confirmatory test in which $FeCl_3$ reacts with potassium ferrocyanide solution to form a deep blue complex precipitate of $Fe_4[Fe(CN)_6]_3$.

Sodium Aluminate Formation

The reaction where gelatinous white $Al(OH)_3$ dissolves in $NaOH$ to form soluble $NaAlO_2$, which subsequently reprecipitates as $Al(OH)_3$ when boiled with solid $NH_4Cl$.

Group IV Basic Radicals

The cations $Zn^{2+}$, $Mn^{2+}$, $Ni^{2+}$, and $Co^{2+}$ precipitated as sulphides ($ZnS$, $MnS$, $NiS$, $CoS$) by passing $H_2S$ gas in the presence of $NH_4OH$ and $NH_4Cl$.

Dimethylglyoxime Test for Nickel

A confirmatory test where $Ni^{2+}$ in the presence of excess $NH_4OH$ reacts with dimethylglyoxime to form a distinctive rosy red chelate precipitate.

Permanganic Acid Oxidation Test for Manganese

A confirmatory test where $MnO_2$ obtained from $MnS$ is heated with concentrated $HNO_3$ and red lead ($Pb_3O_4$) or $PbO_2$ to oxidize $Mn^{2+}$ to pink/purple $HMnO_4$.

Potassium Cobaltinitrite Test

A confirmatory test where $Co^{2+}$ treated with excess acetic acid ($CH_3COOH$) and potassium nitrite ($KNO_2$) yields a yellow precipitate of $K_3[Co(NO_2)_6]$.

Group V Basic Radicals

The alkaline earth cations $Ba^{2+}$, $Sr^{2+}$, and $Ca^{2+}$ precipitated as insoluble white carbonates ($BaCO_3$, $SrCO_3$, $CaCO_3$) by $(NH_4)_2CO_3$ in the presence of $NH_4OH$ and $NH_4Cl$.

Disodium Hydrogen Phosphate Test for Magnesium

A Group VI confirmatory reaction where $Mg^{2+}$ reacts with $Na_2HPO_4$ solution in the presence of $NH_4OH$ to precipitate white magnesium ammonium phosphate ($Mg(NH_4)PO_4$).

Nessler's Reagent Test for Ammonium

A confirmatory test for the $NH_4^+$ cation where addition of Nessler's reagent to an aqueous solution produces a brown coloration or precipitate.