Inorganic Chemistry Class 12 Notes

• Group 15 (N, P, As, Sb, Bi): nitrogen is a gas, P and As solids; hydrides NH₃, PH₃, etc. Ammonia is the strongest base.
• Group 16 (O, S, Se, Te): ozone O₃ is an allotrope; sulphur forms many allotropes (rhombic, monoclinic); H₂SO₄ is a strong dibasic acid.
• Group 17 (halogens): reactivity decreases down the group; fluorine is the most electronegative element.
• Group 18 (noble gases): chemically inert, with Xe forming stable compounds with F and O (e.g. XeF₂, XeF₄).

• Variable oxidation states — e.g. Mn shows +2 to +7.
• Colour arises from d-d transitions.
• Magnetic properties from unpaired d-electrons.
• Catalytic activity: Fe in Haber process, V₂O₅ in contact process, Ni in hydrogenation.
• High melting points due to strong metallic bonding from d-electrons.

• Lanthanides (Ce–Lu): show +3 oxidation state predominantly, lanthanide contraction (steady decrease in ionic radius with atomic number).
• Actinides (Th–Lr): radioactive, show variable oxidation states.
• Lanthanide contraction arises because the 4f electrons poorly shield the increasing nuclear charge.
• Uses: mischmetal in lighter flints, lanthanides in magnets and phosphors.

• Strong-field ligands (CN⁻, CO) cause large Δo and give low-spin complexes.
• Weak-field ligands (Cl⁻, H₂O) cause small Δo and give high-spin complexes.
• Spectrochemical series:
• ${\text{I}}^{-}<{\text{Br}}^{-}<{\text{Cl}}^{-}<{\text{F}}^{-}<{\text{OH}}^{-}<{\text{H}}_2\text{O}<{\text{NH}}_3<\text{en}<{\text{CN}}^{-}<\text{CO}$
• .
• Werner's theory explained primary (ionisable) vs secondary (coordination) valence.

• Geometrical (cis/trans) — depends on arrangement of ligands.
• Optical (d/l) — non-superimposable mirror images.
• Linkage isomerism — ligand binds through different donor atoms (e.g. -NO₂ vs -ONO).
• Ionisation isomerism — different ions in the coordination sphere vs solution.
• Coordination isomerism — exchange of ligands between cationic and anionic complexes.

Inorganic qualitative analysis uses group reagents to precipitate cations: H₂S, NH₄OH and (NH₄)₂S separate ions into groups. Volumetric analysis includes redox titrations (KMnO₄, K₂Cr₂O₇) and gravimetric methods.

• Cation group separation based on solubility products of sulphides and hydroxides.
• Confirmatory tests: flame test, borax bead test, sodium carbonate extract tests.
• Redox titrations: self-indicating KMnO₄ (pink) and K₂Cr₂O₇ with diphenylamine indicator.

Example: Find the oxidation state of Cr in $[{\text{Cr(NH}}_3{)}_4{\text{Cl}}_2{]}^{+}$.

Solution: NH₃ is neutral, Cl is -1 (two Cl = -2), overall charge +1, so $x+0-2=+1\Rightarrow x=+3$. Cr is in the +3 oxidation state.

Exercises (NCERT Q1–Q2)

• 1) Q1. Exercise question 1
• 2) Q2. Exercise question 2

Answers at a glance

1. 1
   Q1 → Answer 1
2. 2
   Q2 → Answer 2

MCQ Questions

1 Mark Questions

• Q1 (1M)
• Q2 (1M)
• Q3 (1M)
• Q4 (1M)

2 Mark Questions

• Q1 (2M)
• Q2 (2M)
• Q3 (2M)

3 Mark Questions

• Q1 (3M)
• Q2 (3M)
• Q3 (3M)

5 Mark Questions

• Q1 (5M)
• Q2 (5M)

Assignments walk the chapter's topics in order; the tests follow the current CBSE blueprint (MCQ/VSA, 2M, 3M and 5M questions) with answer keys. They will appear here as direct download links.