Exam Master Review Sheet - Salt Analysis

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EXAM MASTER REVIEW SHEET

Qualitative Inorganic Analysis (Salt Analysis)

Strategic Identification Logic for JEE & NEET

1. Preliminary Dry Tests

Flame Test

Crimson Red: \(Li^+\)
Golden Yellow: \(Na^+\)
Violet/Lilac: \(K^+\)
Brick Red: \(Ca^{2+}\)
Crimson: \(Sr^{2+}\)
Apple Green: \(Ba^{2+}\)

Borax Bead Test (\(Na_2B_4O_7 \cdot 10H_2O\))

Forms \(NaBO_2 + B_2O_3\)

• Blue: \(Co^{2+}\) (Oxidizing & Reducing)
• Green: \(Cr^{3+}\)
• Sky Blue: \(Cu^{2+}\) (Oxidizing)
• Yellow/Brown: \(Fe^{3+}\)

2. Anionic Analysis (Groups)

Group I: Dilute \(H_2SO_4\)

\(CO_3^{2-}\) Brisk effervescence (\(CO_2\))

\(S^{2-}\) Rotten egg smell (\(H_2S\))

\(SO_3^{2-}\) Burning sulfur smell (\(SO_2\))

\(NO_2^-\) Pungent brown fumes (\(NO_2\))

Group II: Concentrated \(H_2SO_4\)

• \(Cl^-\): Pungent fumes (\(HCl\)); White dense fumes with \(NH_3\).
• \(Br^-\): Reddish-brown fumes (\(Br_2\)); Intense on adding \(MnO_2\).
• \(I^-\): Deep Violet fumes (\(I_2\)); Turns starch paper blue.
• \(NO_3^-\): Light brown fumes; Intense on adding Cu turnings (\(NO_2\)).
• \(C_2O_4^{2-}\): Evolution of \(CO + CO_2\); burns with blue flame.

3. High-Yield Confirmatory Tests

Chromyl Chloride Test (\(Cl^-\) only)

\[ \text{Salt} + K_2Cr_2O_7 + \text{conc. } H_2SO_4 \xrightarrow{\Delta} \underbrace{CrO_2Cl_2 \uparrow}_{\text{Deep Red Vapours}} \]

*Vapours in \(NaOH\) \(\to\) Yellow solution. Add lead acetate \(\to\) Yellow ppt (\(PbCrO_4\)).*

Brown Ring Test (\(NO_3^-\))

Freshly prepared \(FeSO_4\) + conc. \(H_2SO_4\) along sides.
Complex: \([Fe(H_2O)_5(NO)]^{2+}\)
Note: O.S. of \(Fe\) is +1 in this complex.

Prussian Blue Test (\(Fe^{3+}\))

React with Potassium Ferrocyanide:
\[ 4Fe^{3+} + 3[Fe(CN)_6]^{4-} \to \underbrace{Fe_4[Fe(CN)_6]_3}_{\text{Prussian Blue}} \]

4. Systematic Grouping of Cations

Group	Cations	Group Reagent	Ppt Form
0	\(NH_4^+\)	\(NaOH\) (Heat)	Ammonia gas
I	\(Pb^{2+}, Ag^+, Hg_2^{2+}\)	Dilute \(HCl\)	Chlorides
II	\(Cu^{2+}, Cd^{2+}, Pb^{2+}, As^{3+}\)	\(H_2S\) + Dil. \(HCl\)	Sulphides
III	\(Fe^{3+}, Al^{3+}, Cr^{3+}\)	\(NH_4OH\) + \(NH_4Cl\)	Hydroxides
IV	\(Zn^{2+}, Mn^{2+}, Co^{2+}, Ni^{2+}\)	\(H_2S\) + \(NH_4OH\)	Sulphides
V	\(Ba^{2+}, Sr^{2+}, Ca^{2+}\)	\((NH_4)_2CO_3\) + \(NH_4OH\)	Carbonates
VI	\(Mg^{2+}\)	\(Na_2HPO_4\)	Phosphates

5. Miscellaneous Identifications

Nessler's Reagent (\(K_2HgI_4\))

Tests for \(NH_4^+\). Forms Brown ppt of Iodide of Millon's base (\(NH_2 \cdot HgO \cdot HgI\)).

Group III Principle (\(K_{sp}\) vs \(Q\))

\(NH_4Cl\) is added to suppress ionization of \(NH_4OH\) (Common Ion Effect). This ensures only Group III hydroxides (\(K_{sp}\) is low) are precipitated.

\(AgBr\) and \(AgI\) are insoluble in \(NH_4OH\) | \(AgCl\) is soluble.

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