Chem notesInorganicSalt Analysis
Independent topic page
Treat salt analysis as controlled Ksp, complexation, acid-base, and redox chemistry rather than a list of colours.
01. Group reagents control precipitating-ion concentration so only salts with sufficiently small ionic products precipitate — the same Qsp > Ksp gate used in ionic equilibrium.
02. Common-ion suppression, buffer control, and complex formation create selectivity; washing/dissolving confirms identity.
03. Anion tests must separate gas evolution, precipitation, and redox observations and account for interfering ions. Fluoride is outside the AgNO₃ halide scheme in the official syllabus.
04. A colour is supporting evidence, never a complete identification without reagent and solubility behaviour.
05. Group reagents are controlled precipitation equilibria — pH, common ion and complexation decide which sulphides or hydroxides appear.
06. Colour is a hint, never a confirmation; write the decisive precipitate or complex equation before locking an ion.
07. Anion schemes need fresh portions and interference control: acid before AgNO₃ halide tests, and carbonate vs bicarbonate follow-ups matter.
Official · 2026
Official syllabus points for Qualitative Inorganic Analysis only — not the full Inorganic portion map. Portion hub: Inorganic · Inorganic analysis.
No topic-specific exclusions flagged — finish the unit points below for Salt Analysis.
Source: https://jeeadv.ac.in/documents/jee-advanced-2026-syllabus.pdf
Exam focusCation/anion detection and salt-analysis logic.
Syllabus points
2020–2026 paper weight
Topic match inside parent portion Inorganic (23.7% of Chemistry tags). Stats below are portion backdrop; matched subtopics show where Qualitative Inorganic Analysis sits.
Portion-wide type/difficulty mix lives on the Inorganic analysis — not repeated here so this page stays on Salt Analysis.
01. Dominant subtopics: Coordination (24), Metallurgy (13), Qualitative (9), Bonding (6).
Cross-topic stems
Advanced rarely asks a chapter in isolation. These are tagged multi-idea Chemistry stems that touch Qualitative Inorganic Analysis — practise the knowledge bridge, not only the single-chapter drill.
Step 1: push each reagent in order to get intermediates Q, R, S, T. Step 2: recognise the heterocyclic closure in T. Step 3: apply Tollens (and related tests) only to the structure that still has the oxidisable group (S).
Mechanism memory plus lab-test logic in one multi-correct/sequence item.
After every synthesis map, annotate which intermediates pass Tollens/Fehling/iodoform.
Step 1: decode practical/analysis data into a count or identification. Step 2: push named-reaction reagents to the major product / stoichiometric ask. Step 3: keep Physical mixed NUMs mentally separate so Organic logic is not diluted.
Organic numericals feel unfamiliar if you only practised MCQ mechanisms.
Convert two named reactions per week into a numerical ask (moles, isomers, mass).
Why methods matter
Selective precipitation is equilibrium chemistry controlled through pH, common ions and complexation.
Explains selective precipitation instead of memorising groups.
Do thisWrite the controlled ion and compare Qsp with Ksp.
Explains selective precipitation instead of memorising groups.
Acid suppresses H₂S ionisation, so Group II sulphides precipitate first.
A single colour is rarely unique.
Do thisRecord colour + solubility + confirmatory transformation.
A single colour is rarely unique.
AgCl: white, darkens in light, dissolves in dilute NH₃.
Separates hydroxide dissolution from ammine complexation.
Do thisTest precipitate in excess NaOH and NH₃ separately.
Separates hydroxide dissolution from ammine complexation.
Al(OH)₃ dissolves in excess NaOH; Cu(OH)₂ gives deep-blue ammine with NH₃.
Prevents the reagent acid from adding the tested anion.
Do thisUse fresh portions and acidify with the specified non-interfering acid.
Prevents the reagent acid from adding the tested anion.
Use HNO₃, not HCl, before AgNO₃ halide testing.
Processed examples
Read the impact line first. Then notice which family/model was chosen. The solution is written the way your rough sheet should look in the hall.
Why is H₂S passed in acidic medium for group-II cations?
This stem rewards early recognition of the group precipitation model.
Model chosenSuppress sulphide ion using common-ion acidity.
AnswerTo maintain a low, selective [S²⁻]
Takeaway: pH controls selective precipitation.
A blue Cu(OH)₂ precipitate dissolves in excess NH₃. Identify the product and colour.
This stem rewards early recognition of the confirmatory complex test model.
Model chosenApply ammine-complex formation.
Answer[Cu(NH₃)₄]²⁺, deep blue
Takeaway: Complexation can redissolve a precipitate.
A solution has 0.010 M each Zn²⁺ and Cu²⁺. If [S²⁻]=10⁻¹⁸ M, Ksp(CuS)=10⁻³⁶ and Ksp(ZnS)=10⁻²⁴, determine selective precipitation.
This Advanced-level variation couples hidden constraints with the group precipitation model.
Model chosenCompare each ionic product with its Ksp.
AnswerBoth CuS and ZnS precipitate
Takeaway: Selective analysis requires checking every candidate Ksp.
Reusable models
Advanced stems cluster. Name the family in 10–15s, write the fast model, then run the same path. Do not invent a new plan each time.
Looks likeCation separation by HCl, H₂S, NH₄OH or carbonate
Fast modelControl the precipitating-ion concentration through pH and common ion.
Recognition fixes the model before arithmetic begins.
Do not start blind expansion or casework before identifying the governing model.
Looks likeCharacteristic colour, dissolution or reprecipitation
Fast modelTrack the metal through precipitate and complex formation.
Recognition fixes the model before arithmetic begins.
Do not start blind expansion or casework before identifying the governing model.
Looks likeGas evolution, ring test or precipitate test
Fast modelUse preliminary acid behavior before the confirmatory test.
Recognition fixes the model before arithmetic begins.
Do not start blind expansion or casework before identifying the governing model.
Looks likeSeveral ions with interfering reactions
Fast modelOrder operations by selectivity, not by memorized isolated tests.
Recognition fixes the model before arithmetic begins.
Do not start blind expansion or casework before identifying the governing model.
Hall timing
Decide whether the controlling idea is trend, structure, equilibrium, redox, or a named preparation/test.
Fix oxidation state, charge balance, medium, and periodic position; do not answer from a vague trend.
For multi-correct questions, independently verify every species and every condition.
Reject conclusions that silently change medium, coordination number, temperature, or oxidation state.
After the model is locked
ionic product Qsp > Ksp ⇒ precipitation
Decide selective group precipitation.
dil. HCl → AgCl, PbCl₂, Hg₂Cl₂
Separate sparingly soluble chlorides.
H₂S in acidic medium: low [S²⁻]
Precipitate very insoluble sulphides.
NH₄Cl + NH₄OH: buffered low [OH⁻]
Precipitate Fe³⁺/Al³⁺/Cr³⁺ hydroxides selectively.
H₂S/(NH₄)₂S in ammoniacal medium: higher [S²⁻]
Precipitate Zn²⁺/Mn²⁺/Ni²⁺/Co²⁺ sulphides.
(NH₄)₂CO₃ with NH₄Cl/NH₄OH → Ba/Sr/Ca carbonates
Separate alkaline-earth group.
NO₃⁻ → NO; [Fe(H₂O)₅(NO)]²⁺ gives brown ring
Confirm nitrate carefully at the liquid interface.
AgCl white soluble dil NH₃; AgBr cream soluble conc NH₃; AgI yellow insoluble
Distinguish Cl⁻/Br⁻/I⁻ after acidifying with HNO₃.
Make it automatic