#SIGNIFICANTFIGURES
🌱 Definition
Digits which convey certainty + one uncertain digit

⭐ Rules to Count Significant Figures
✔️ All non-zero digits → significant
✔️ Zeros between non-zero → significant
✔️ Leading zeros → ❌ not significant
✔️ Trailing zeros → significant only with decimal

📌 Examples:
0.0045 → 2 SF
2.300 → 4 SF
1500 → 2 SF (without decimal)

➕➖ Addition / Subtraction
Result → least decimal places
📌 Example:
12.11 + 0.2 = 12.3

✖️➗ Multiplication / Division
Result → least significant figures
📌 Example:
2.5 × 1.23 = 3.1 (2 SF)

🔢 Rounding Off Rules
Next digit < 5 → same
Next digit ≥ 5 → +1
📌 2.34 → 2.3
📌 2.36 → 2.4

#NEETHOTPOINTS
✔️ Exact numbers → infinite SF
✔️ Unit conversion → SF maintained
✔️ Final answer rounding last step

@Ayano1me @Neetugpoll @Neetugquiz

Ans eve m upload hoga sb try krna

Question 1 (Concept + Limiting Reagent):

A mixture contains 4 g H₂ and 32 g O₂.
They react according to:
2H2+O2= 2H2O
Find:
(i) Limiting reagent
(ii) Mass of water formed
(iii) Mass of excess reactant left

Question 2 (Gas + Stoichiometry + Trick)

At STP, 11.2 L of a gaseous hydrocarbon reacts completely with excess O₂ to produce 44 g CO₂.
Identify the hydrocarbon.

Question 3 (Equivalent + Redox + Stoichiometry )

A 10 g mixture of Na₂CO₃ and NaHCO₃ is completely neutralised by 200 mL of 1 N HCl.
Find the mass percentage of Na₂CO₃ in the mixture.

#SIGNIFICANTFIGURES

Question :1 Evaluate the result with correct significant figures:
(2.36+0.040) +1.2

Question 2
The mass of a cube is measured as 2.50 g and each edge is measured as 1.20 cm.
Calculate the density of the cube with correct significant figures.



20 imp topic chemistry series start

What is a Solution?
A homogeneous mixture of: ✔️ Solute (less amount)
✔️ Solvent (more amount)
📌 Examples:
Sugar in water
Salt in water
⭐ Types of Solutions (Based on Raoult’s Law)
🔹 #IdealSolution
📌 Obeys Raoult’s law at all concentrations
✔️ ΔHmix = 0
✔️ ΔVmix = 0
✔️ A–A ≈ B–B ≈ A–B interactions
📌 Examples:
Benzene + Toluene
n-Hexane + n-Heptane

#NonIdealSolution
📌 Does NOT obey Raoult’s law
✔️ ΔHmix ≠ 0
✔️ ΔVmix ≠ 0
✔️ A–B ≠ A–A or B–B interactions
⭐ Types of Non-Ideal Solutions

1️⃣ #PositiveDeviation
✔️ A–B interactions weaker
✔️ Vapour pressure ↑
✔️ Endothermic mixing (ΔH > 0)
📌 Examples:
Ethanol + Acetone
Acetone + CS₂

2️⃣ #NegativeDeviation
✔️ A–B interactions stronger
✔️ Vapour pressure ↓
✔️ Exothermic mixing (ΔH < 0)
📌 Examples:
Chloroform + Acetone
HNO₃ + Water

⭐ Azeotropes
📌 Constant boiling mixture
📌 Vapour composition = Liquid composition
✔️ Positive deviation → Minimum boiling azeotrope
✔️ Negative deviation → Maximum boiling azeotrope

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#ColligativeProperties
Properties depending on number of solute particles, not nature

⭐ 4 Colligative Properties

1️⃣ Relative Lowering of Vapour Pressure
📌 ΔP / P° = n₂ / n₁
📌 Raoult’s law based

2️⃣ Elevation of Boiling Point
📌 ΔTb = Kb · m
✔️ Boiling point ↑
✔️ Kb → Molal elevation constant
3️⃣ Depression of Freezing Point
📌 ΔTf = Kf · m
✔️ Freezing point ↓
✔️ Kf → Molal depression constant
4️⃣ Osmotic Pressure
📌 π = CRT
✔️ Most reliable colligative property
✔️ Used to find molar mass


⭐ #Van’tHoffFactor (i)
📌 i = Actual number of particles / Expected number
✔️ Association → i < 1
✔️ Dissociation → i > 1
✔️ Non-electrolyte → i = 1
📌 Modified formulas:
ΔTb = iKb m
ΔTf = iKf m
π = iCRT

#NEETHOTPOINTS
✔️ Ideal solution → ΔHmix = 0
✔️ Positive deviation → Weak A–B attraction
✔️ Negative deviation → Strong A–B attraction
✔️ Azeotrope → Constant boiling mixture
✔️ Most accurate colligative property → Osmotic pressure

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#ElectrochemicalCell
Device that converts chemical energy → electrical energy
📌 Components:
Anode → Oxidation
Cathode → Reduction
📌 Electron flow: Anode → Cathode
🔋 EMF of Cell
📌 E°cell = E°cathode − E°anode
✔️ Standard conditions: 1 M, 1 atm, 298 K

#NernstEquation (Very High Yield )
🌱 Used to calculate cell potential at non-standard conditions
⭐ General form:

E=E°-RT/NF LN Q

At 298K

E=E°-0.0591/n LogQ

Where
E = Cell potential
E° = Standard potential
n = Number of electrons transferred
Q = Reaction quotient

#Specialcases (Direct MCQ)
✔️ For concentration cell:

E=0.059/n log C2/C1

✔️ At equilibrium:
E = 0
Q = K
E°=0.059/n logK

@Ayano1me @Neetugpoll

Conductivity
🌱 Electrical Conductance (G)
📌 Reciprocal of resistance
G=1/R
Unit: Siemens (S)

⭐ Specific Conductivity (κ)
Conductance of solution of: ✔️ 1 cm length
✔️ 1 cm² area
Depends on:
Concentration
Temperature
Nature of electrolyte

⭐ Molar Conductivity (Λm)
(Λm)=k×1000/C
Unit: S cm² mol⁻¹

📌 C = molarity
✔️ Increases on dilution
✔️ Maximum value at infinite dilution → Λ°m

Strong vs Weak Electrolyte
Feature :Strong :Weak
Ionisation :Complete :Partial
Λm with dilution :Slight ↑ :Sharp ↑
Kohlrausch law :✔️ Applicable
: ✔️ Applicable

#Kohlrausch’s Law
At infinite dilution:
Λm°=(Λm°+) + ((Λm°_)

✔️ Helps calculate:
Λ°m of weak electrolytes
Degree of dissociation
Ka, Kb

#NEETHOTPOINTS
✔️ Nernst eqn at 298 K → 0.0591/n
✔️ At equilibrium → E = 0
✔️ Unit of κ → S cm⁻¹
✔️ Λm increases with dilution
✔️ Maximum conductivity → Infinite dilution

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#ChemicalKinetics

⭐ First Order Reaction
🌱 Definition
Reaction whose rate depends on concentration of one reactant raised to power 1

📌 Rate law:
Rate =k(A)

🔢 Integrated Rate Equation
K=2.303/t log (A)•/(A)
📌 Where:
� = rate constant
� = time
� = initial concentration
� = concentration at time t

#Halflife (t½)
Time for concentration to become half
t1/2=0.693/k

⭐Independent of initial concentration (#veryimp )
Units
✔️ Rate constant (k) → s⁻¹
Graph (Direct MCQ)
✔️ log[A] vs t → Straight line
✔️ Slope → –k/2.303

Examples
✔️ Radioactive decay
✔️ Decomposition of N₂O₅
✔️ Acid hydrolysis of esters (pseudo-first order)

#NEETHOTPOINTS (1st Order)
✔️ Half-life independent of concentration
✔️ Unit of k → s⁻¹
✔️ Straight line graph → log[A] vs t
✔️ Pseudo-first order → One reactant in excess

@Ayano1me @Neetugpoll @NeetugQuiz

#Arrhenius Equation
🌱 Shows effect of temperature on rate constant
⭐ Equation

K=Ae^-ea/Rt
📌 Where:
� = rate constant
� = Arrhenius factor / frequency factor
� = Activation energy
� = Gas constant
� = Temperature (K)

⭐ Log Form (Most Used)
LogK=logA-Ea/2.303RT

⭐ Two Temperature Form
Log K2/K2=Ea/2.303R(T2-T1/T2•T1)

#Graph
✔️ log k vs 1/T → Straight line
✔️ Slope → –Ea / 2.303R
✔️ Intercept → log A

#Effect of Catalyst
✔️ Lowers Ea
✔️ Does NOT change ΔH
✔️ Increases rate

#NEETHOTPOINTS
✔️ Higher Ea → Slower reaction
✔️ Catalyst → lowers Ea
✔️ Temperature ↑ → k ↑
✔️ Straight line → log k vs 1/T
✔️ Unit of Ea → J mol⁻¹

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General Physical Properties (d-Block)
⭐ Atomic & Ionic Size
✔️ Size decreases from left → right (↑ nuclear charge)
✔️ After middle → almost constant (poor shielding by d-electrons)

⭐ Density
✔️ Increases from 3d → 4d → 5d
📌 Reason:
Increase in atomic mass
Lanthanide contraction (5d elements smaller → higher density)

⭐ Melting & Boiling Points
✔️ Very high
📌 Reason:
Strong metallic bonding
Involvement of d-electrons
📌 Exceptions:
Zn, Cd, Hg → low m.p.
✔️ Hg → liquid (weak metallic bonding)

⭐ Variable Oxidation States
✔️ Due to similar energy of (n−1)d & ns electrons
📌 Example:
Fe → +2, +3
Mn → +2 to +7

⭐ Magnetic Properties
✔️ Paramagnetic → unpaired electrons
✔️ Diamagnetic → all paired
📌 Magnetic moment:
U=√n(n+2)

⭐ Colour
✔️ Due to d–d transitions
✔️ Zn²⁺, Cd²⁺ → colourless (d¹⁰)
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🌟 Lanthanide Contraction (VERY HIGH YIELD 🔥)
🌱 Definition
Gradual decrease in atomic & ionic radii of lanthanides from La → Lu
#Reason
✔️ Poor shielding effect of 4f-electrons
✔️ Effective nuclear charge increases
🔥 Consequences of Lanthanide Contraction
1️⃣ Similar size of 4d & 5d elements
📌 Zr ≈ Hf
📌 Chemical properties similar
2️⃣ High density of 5d elements
📌 Reason:
Smaller size
Higher mass
3️⃣ Difficulty in separation of lanthanides
📌 Very similar radii & properties
4️⃣ Basic strength of hydroxides decreases
📌 La(OH)₃ > Lu(OH)₃
5️⃣ Decrease in ionic radii of Ln³⁺ ions
📌 Affects coordination number & complex formation
#NEETHOTPOINTS
✔️ Poor shielding → 4f electrons
✔️ Cause of Zr–Hf similarity → Lanthanide contraction
✔️ Colour in d-block → d–d transition
✔️ Colour in f-block → f–f transition
✔️ Most stable oxidation state of lanthanides → +3
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#CoordinationCompounds
Valence Bond Theory (VBT) & Isomerism (NCERT • NEET)

🌱 Coordination Compound
A compound in which: ✔️ Central metal atom/ion
✔️ Surrounded by ligands
✔️ Linked by coordinate bonds
📌 Example: [Co(NH₃)₆]Cl₃

⭐ #ValenceBondTheory (VBT)
🌱 Explains: ✔️ Geometry
✔️ Magnetic behaviour
✔️ Hybridisation

🔹 Postulates of VBT
✔️ Metal ion provides empty orbitals
✔️ Ligands donate lone pair
✔️ Overlap → coordinate bond
✔️ Paired/unpaired electrons decide magnetic nature

⭐ #Hybridisation&Geometry
Hybridisation :Geometry
d²sp³ / sp³d² :Octahedral
sp³ : Tetrahedral
dsp² : Square planar

#InnerOrbitalvsOuterOrbitalComplex
⭐ Inner Orbital Complex (Low spin)
✔️ Uses (n−1)d orbitals
✔️ Pairing of electrons occurs
✔️ Strong field ligands
📌 Example:
[Co(NH₃)₆]³⁺ → d²sp³ (octahedral)

⭐ Outer Orbital Complex (High spin)
✔️ Uses nd orbitals
✔️ No pairing
✔️ Weak field ligands
📌 Example:
[FeF₆]³⁻ → sp³d² (octahedral)

#MagneticNature (VBT)
✔️ Unpaired e⁻ → Paramagnetic
✔️ Paired e⁻ → Diamagnetic
📌 Example:
[Ni(CN)₄]²⁻ → Diamagnetic (dsp²)
[NiCl₄]²⁻ → Paramagnetic (sp³)
⚠️ Limitations of VBT
❌ Cannot explain colour
❌ Cannot explain strong vs weak ligands clearly
❌ No quantitative explanation of spectra

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Isomerism in Coordination Compounds
🌱 Compounds with same formula but different arrangement

⭐ #Structural Isomerism
1️⃣ Ionisation Isomerism
✔️ Exchange between ligand & counter ion
📌 Example:
[Co(NH₃)₅SO₄]Br
[Co(NH₃)₅Br]SO₄

2️⃣ Solvate (Hydrate) Isomerism
✔️ Water inside or outside coordination sphere
📌 Example:
[Cr(H₂O)₆]Cl₃
[Cr(H₂O)₅Cl]Cl₂·H₂O

3️⃣ Linkage Isomerism
✔️ Ambidentate ligands
📌 Example:
NO₂⁻ → nitro / nitrito
SCN⁻ → thiocyanato / isothiocyanato

4️⃣ Coordination Isomerism
✔️ Between cationic & anionic complexes
📌 Example:
[Co(NH₃)₆][Cr(CN)₆]
[Cr(NH₃)₆][Co(CN)₆]

⭐ #Stereoisomerism
1️⃣ Geometrical Isomerism
✔️ cis–trans
📌 Examples:
[Pt(NH₃)₂Cl₂]
[Co(NH₃)₄Cl₂]⁺

2️⃣ Optical Isomerism
✔️ Non-superimposable mirror images
✔️ d & l forms
📌 Example:
[Co(en)₃]³⁺

#NEETHOTPOINTS
✔️ Square planar → dsp²
✔️ Strong ligand → pairing → inner orbital
✔️ Ambidentate ligand → linkage isomerism
✔️ cis–trans in square planar & octahedral
✔️ Optical isomerism → no plane of symmetry

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#Haloalkanes
Alkanes in which H is replaced by halogen (F, Cl, Br, I)
📌 General formula: R–X
🔄 Nucleophilic Substitution Reactions
⭐ SN1 Reaction (Unimolecular)
🌱 Rate depends on only one species
📌 Rate = k[R–X]
🔹 Mechanism (2 Step)
1️⃣ R–X → R⁺ + X⁻ (Slow, RDS)
2️⃣ R⁺ + Nu⁻ → R–Nu (Fast)
⭐ Key Features
✔️ Formation of carbocation
✔️ Rearrangement possible
✔️ Racemisation occurs
✔️ Favoured by polar protic solvents
⭐ Order of Reactivity
3° > 2° > 1° > CH₃
📌 Reason: Carbocation stability
⭐ SN2 Reaction (Bimolecular)
🌱 Single step reaction
📌 Rate = k[R–X][Nu⁻]
🔹 Mechanism
✔️ Backside attack
✔️ Transition state formation
✔️ Simultaneous bond making & breaking
⭐ Key Features
✔️ No carbocation
✔️ No rearrangement
✔️ Inversion of configuration (Walden inversion)
✔️ Favoured by polar aprotic solvents
⭐ Order of Reactivity
CH₃ > 1° > 2° >> 3°
📌 Reason: Steric hindrance

SN1 vs SN2 (Direct MCQ)
Feature :SN1 :SN2
Steps :2 :1
Rate depends on :R–X :R–X & Nu⁻
Intermediate :Carbocation :None
Rearrangement :✔️ :❌
Stereochemistry :Racemisation
: Inversion
Favoured by ;3° haloalkane
: 1° haloalkane

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