Inorganic Reasoning and Qualitative Analysis

80 lessons, pages 2601–2680.

What Is Qualitative Inorganic Analysis? — Identifying ions from their characteristic behaviour rather than measuring amounts
The Logic of Systematic Analysis — Separation by groups, elimination and confirmation as a reasoning chain
Solubility Rules Revisited — Which salts dissolve and why the patterns underpin every separation
Solubility Product and Precipitation — Comparing ionic product with Ksp to predict whether a solid forms
The Common Ion Effect in Analysis — Suppressing solubility and controlling ion concentrations deliberately
Selective Precipitation — Using differences in Ksp to separate ions from a mixture
pH Control and Sulfide Precipitation — How acidity governs sulfide ion concentration and which sulfides form
Complex Formation and Dissolving Precipitates — Ammonia, hydroxide and chloride complexes that pull solids back into solution
Amphoteric Hydroxides in Analysis — Aluminium, zinc and lead hydroxides dissolving in excess alkali
Observations as Evidence — Colours, precipitates, gases and smells as data for inference
Preliminary Tests on an Unknown Salt — Appearance, colour, solubility and effect of heating as first clues
Flame Tests and Electronic Transitions — Why excited metal ions emit characteristic colours
Interpreting Flame Colours — Lithium, sodium, potassium, calcium, strontium, barium and copper compared
Classifying Cations into Analytical Groups — The classical group scheme and the reagent that defines each group
Group I Cations: Insoluble Chlorides — Silver, lead(II) and mercury(I) and why their chlorides precipitate
Distinguishing the Group I Cations — Hot-water solubility of lead chloride and ammonia behaviour of silver chloride
Group II Cations: Sulfides in Acid — Very low Ksp sulfides such as copper, cadmium, bismuth and tin
Group III Cations: Hydroxides in Buffered Ammonia — Iron(III), aluminium and chromium(III) hydroxide precipitation
Group IV Cations: Sulfides in Alkaline Medium — Zinc, manganese, nickel and cobalt sulfides
Group V Cations: Insoluble Carbonates — Calcium, strontium and barium separated as carbonates
Group VI Cations: The Soluble Remainder — Magnesium, sodium, potassium and ammonium identified last
Testing Cations with Sodium Hydroxide — Precipitate colours and behaviour in excess alkali
Testing Cations with Aqueous Ammonia — Hydroxide precipitation versus ammine complex formation
Identifying Copper(II) Ions — Blue hydroxide and deep blue tetraamminecopper(II)
Identifying Iron(II) and Iron(III) Ions — Green and rust-brown hydroxides, thiocyanate and oxidation in air
Identifying Zinc, Aluminium and Lead Ions — Three white hydroxides told apart by ammonia and other reagents
Identifying Chromium, Manganese, Nickel and Cobalt Ions — Coloured hydroxides and complexes of the later transition metals
Identifying Group 2 Cations — Sulfate and hydroxide solubility trends from magnesium to barium
Identifying the Ammonium Ion — Liberating ammonia with warm alkali and detecting it with damp litmus
Cation Analysis: Putting It Together — Designing a reasoning path for a mixture of cations
Classifying Anions for Analysis — Gas-evolving, precipitating and redox-active anion families
Identifying Carbonate and Hydrogencarbonate — Effervescence with acid and the limewater test for carbon dioxide
Identifying Sulfite and Sulfide — Sulfur dioxide and hydrogen sulfide as evidence, handled conceptually
Identifying Sulfate — Barium sulfate precipitation and why the solution is acidified first
Halide Ions and Silver Nitrate — White, cream and yellow silver halide precipitates
Confirming Halides with Ammonia — Solubility of silver halides in dilute and concentrated ammonia
Halides and Concentrated Sulfuric Acid — Increasing reducing power from chloride to iodide
Displacement Reactions of Halogens — Using oxidising power order to identify halide ions
Identifying Nitrate and Nitrite — Reduction to ammonia and the brown-ring principle
Identifying Phosphate — Yellow ammonium phosphomolybdate and phosphate reasoning
Identifying Chromate and Dichromate — The pH-dependent chromate-dichromate equilibrium and colour change
Identifying Ethanoate and Oxalate — Organic anions in inorganic analysis
Interfering Ions and How to Remove Them — Why carbonate masks sulfate tests and sulfide masks halide tests
Gas Tests in Qualitative Analysis — Hydrogen, oxygen, carbon dioxide, ammonia, chlorine and sulfur dioxide
Anion Analysis: Putting It Together — Sequencing anion tests so each result is unambiguous
Identifying a Complete Unknown Salt — Combining cation and anion evidence into a single formula
Qualitative Analysis Problem Solving — Deducing identities from a sequence of reported observations
Instrumental Methods Versus Wet Tests — Where spectroscopy and chromatography replace classical tests
Safety Thinking in Inorganic Analysis — Toxic gases, heavy metals and hazard reasoning at a conceptual level
Structural Reasoning in Inorganic Chemistry — Predicting shape, bonding and properties from electron counts
VSEPR for Main-Group Compounds — Electron domains, lone pairs and molecular geometry
Hypervalent Molecules — PCl₅, SF₆ and XeF₄ without invoking d-orbital hybridisation
Structures of the Noble Gas Compounds — Xenon fluorides and oxides as tests of bonding models
Oxoanion Structures — Sulfate, nitrate, phosphate and perchlorate shapes and resonance
Oxoacids and Their Strength — How terminal oxygen count and central atom electronegativity control acidity
Electron-Deficient Compounds — Boron trifluoride, diborane and three-centre two-electron bonds
Polymeric and Chain Structures — Silicates, polyphosphates and aluminium chloride dimers
Allotropy and Structure — Carbon, phosphorus, sulfur and oxygen allotropes compared
Ionic Versus Covalent Character — Fajans' rules, polarisation and the chloride series across a period
Structures of Metal Oxides and Halides — From ionic lattices to molecular oxides and halides across the table
Trends in Oxide Acid-Base Character — Basic, amphoteric and acidic oxides linked to structure
Hydrolysis of Halides — Why SiCl₄ reacts with water but CCl₄ does not
The Inert Pair Effect — Stability of lower oxidation states for thallium, tin, lead and bismuth
Diagonal Relationships — Lithium-magnesium, beryllium-aluminium and boron-silicon similarities
Anomalous Behaviour of Second-Period Elements — Small size, high electronegativity and no low-lying d-orbitals
Crystal Field Reasoning for Colour — d-orbital splitting and why transition metal ions are coloured
Explaining Colours in Qualitative Tests — Linking ligand changes to observed colour changes in analysis
Magnetism and Electron Configuration — Paramagnetism, high-spin and low-spin complexes
Isomerism in Coordination Compounds — Geometric, optical and ionisation isomers as structural evidence
Ligand Substitution and Stability — Stability constants, the chelate effect and colour change
Redox Reasoning with Standard Potentials — Predicting whether oxidation-state changes occur in solution
Stability of Oxidation States in Solution — Disproportionation, comproportionation and Latimer-style reasoning
Hard and Soft Acids and Bases — Explaining sulfide, halide and complex preferences of metal ions
Thermal Stability of Carbonates and Nitrates — Cation polarising power and decomposition patterns
Lattice Energy and Solubility Trends — Balancing lattice and hydration enthalpies to explain group trends
Structural Deduction from Reaction Data — Working back from reactions and properties to a formula and structure
Multi-Step Inorganic Puzzles — Chains of unknowns solved with qualitative and structural evidence
Common Errors in Inorganic Reasoning — Misread observations, missed interferences and overgeneralised trends
Exam Strategy for Qualitative Analysis — Writing observations, inferences and ionic equations precisely
Inorganic Reasoning and Qualitative Analysis: Unit Review — Connecting separations, ion tests and structural principles