Principles of Qualitative Analysis: JEE Advanced PYQ, 2007–2026

Q1 · Chemistry · Principles of Qualitative Analysis

A borate salt is warmed with methanol and concentrated sulphuric acid, and the vapour is ignited. What colour is the flame edge?

• AGreen
• BCrimson
• CYellow
• DBluish-white

Q2 · Chemistry · Principles of Qualitative Analysis

A solution of an unknown salt gives a white precipitate on adding dilute HCl. When the precipitate is filtered off and treated with aqueous ammonia, it turns black. The cation present and the origin of the black colour are:

• AHg₂²⁺; the chloride Hg₂Cl₂ disproportionates to finely divided Hg and Hg(NH₂)Cl
• BPb²⁺; PbCl₂ is converted to black PbO₂ by ammonia
• CAg⁺; AgCl is converted to black Ag₂O by ammonia
• DHg²⁺; HgCl₂ precipitates with HCl and turns black as HgS with ammonia

Q3 · Chemistry · Principles of Qualitative Analysis

In the laboratory test for sulfide ion, S²⁻ reacts with sodium nitroprusside, Na₂[Fe(CN)₅(NO)] (in which NO is present as NO⁺), to give the purple complex Na₄[Fe(CN)₅(NOS)]. In this reaction S²⁻ adds to the coordinated nitrosyl and there is no redox change at the metal. Which statement about the iron centre in the purple anion [Fe(CN)₅(NOS)]⁴⁻ is correct?

• AIron is Fe(II), low-spin d⁶, and the complex is diamagnetic
• BIron is Fe(II), high-spin d⁶, with 4 unpaired electrons
• CIron is Fe(III), low-spin d⁵, with 1 unpaired electron
• DIron is Fe(I), low-spin d⁷, with 1 unpaired electron

Q4 · Chemistry · Principles of Qualitative Analysis

Which cation gives a reddish-brown hydroxide precipitate with NH4OH in the presence of NH4Cl, as in Group III?

• AFe3+
• BCr3+
• CCu2+
• DMn2+

Q5 · Chemistry · Principles of Qualitative Analysis

A colourless aqueous solution of a metal salt gives no precipitate with dilute HCl. With dropwise aqueous NaOH it gives a white gelatinous precipitate that dissolves in excess NaOH. With dropwise aqueous NH3 it gives a white gelatinous precipitate that does NOT dissolve in excess NH3. Which cation is present, and what does the precipitate form in excess NaOH?

• AAl³⁺, forming the soluble tetrahydroxidoaluminate(III) ion, [Al(OH)₄]⁻
• BZn²⁺, forming the soluble tetrahydroxidozincate(II) ion, [Zn(OH)₄]²⁻
• CMg²⁺, forming the soluble tetrahydroxidomagnesate(II) ion, [Mg(OH)₄]²⁻
• DPb²⁺, forming the soluble plumbite ion in excess NaOH

Q6 · Chemistry · Principles of Qualitative Analysis

A borax bead is touched to a salt of a transition metal and heated in the oxidising flame and then in the reducing flame. Which row correctly gives the colour of the cold bead in the oxidising flame and in the reducing flame, respectively?

• ACopper salt: blue; opaque red
• BCobalt salt: blue; green
• CManganese salt: colourless; amethyst violet
• DIron salt: bottle green; yellow

Q7 · Chemistry · Principles of Qualitative Analysis

Which reagent, added to a solution of Ca²⁺ ions, gives a white precipitate that is insoluble in dilute acetic acid?

• APotassium iodide (KI)
• BAmmonium oxalate, (NH₄)₂C₂O₄
• CPotassium ferrocyanide, K₄[Fe(CN)₆]
• DDilute hydrochloric acid, HCl

Q8 · Chemistry · Principles of Qualitative Analysis

The mixed Group II sulphides PbS, CuS, CdS, Bi2S3 and HgS are heated with hot dilute HNO3 and filtered. The black residue is dissolved in aqua regia and the solution is boiled to expel excess acid. SnCl2 solution is then added first dropwise and then in excess. What is observed?

• AA white silky precipitate forms, which turns grey on adding excess SnCl2.
• BA white precipitate forms that stays white however much SnCl2 is added.
• CA yellow precipitate forms, which dissolves in excess SnCl2.
• DA deep blue solution forms, because Cu2+ is carried into the aqua regia solution.

Q9 · Chemistry · Principles of Qualitative Analysis

Two experiments are done separately on a dilute aqueous solution of HgCl2. In the first, KI solution is added dropwise until it is in excess. In the second, SnCl2 solution is added dropwise until it is in excess. Which of the following correctly describes the observations in each experiment?

• AKI: scarlet precipitate of HgI2 that persists in excess. SnCl2: white silky precipitate that persists in excess.
• BKI: scarlet precipitate that dissolves in excess to give a colourless solution. SnCl2: grey precipitate first, which turns white with excess.
• CKI: scarlet precipitate that dissolves in excess to give a colourless solution. SnCl2: white silky precipitate first, which turns grey or black with excess.
• DKI: scarlet precipitate that dissolves in excess to give a colourless solution. SnCl2: white precipitate that dissolves in excess to give a clear solution of Hg²⁺ and Sn⁴⁺.

Q10 · Chemistry · Principles of Qualitative Analysis

Calcium ions are treated with ammonium oxalate in a neutral or ammoniacal medium. Which description of the precipitate is correct?

• AA white precipitate that dissolves in dilute acetic acid
• BA yellow precipitate that is insoluble in dilute HCl
• CA white precipitate insoluble in dilute acetic acid but soluble in dilute HCl
• DNo precipitate, since calcium salts are soluble in all reagents