#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

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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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