Solutions and Solid State - NEET PYQs (2009-2024)

🎯 Overview

Welcome to the comprehensive collection of NEET Previous Year Questions on “Solutions and Solid State” from 2009-2024. This important chapter consistently appears with 3-4 questions annually, covering types of solutions, colligative properties, Raoult’s law, crystal structures, unit cells, and solid-state properties. The questions require both numerical skills and conceptual understanding.

📊 Chapter Analysis & Statistics

Question Distribution

📈 PYQ Distribution (2009-2024):
- Total Questions: 45-55 questions
- Average per year: 3-4 questions
- Difficulty Level: Medium
- Success Rate: 60-75%
- Time per Question: 1.5-2.5 minutes

🎯 Weightage in NEET:
- 3-4 questions per year
- 12-16 marks per year
- 7-9% of Chemistry section
- 20-25% of Physical Chemistry

Topic-wise Distribution

📚 Topic Coverage:
1. Solutions and Colligative Properties: 50% of questions
2. Solid State and Crystal Structures: 50% of questions

🔍 Core Concepts and Formulas

1. Types of Solutions

📊 Solution Components:
- Solute: Substance being dissolved (usually smaller amount)
- Solvent: Substance doing the dissolving (usually larger amount)

🧪 Types of Solutions Based on Solvent:
1. Solid solution: Solid solute in solid solvent (alloys)
2. Liquid solution: Solid/liquid/gas solute in liquid solvent
3. Gaseous solution: Gas mixture (air)

📊 Concentration Terms:
- Molarity (M): Moles of solute/Liters of solution
- Normality (N): Equivalents of solute/Liters of solution
- Molality (m): Moles of solute/Kilograms of solvent
- Mole fraction (x): Moles of component/Total moles
- Mass percent: (Mass of solute/Mass of solution) × 100
- Volume percent: (Volume of solute/Volume of solution) × 100

2. Solubility and Henry’s Law

💧 Solubility:
Maximum amount of solute that can dissolve in given amount of solvent at specific temperature and pressure.

🌊 Henry's Law (for gases):
"At constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid."

Mathematically: p = KH × x
Where:
- p = Partial pressure of gas
- x = Mole fraction of gas in solution
- KH = Henry's law constant

📊 Factors Affecting Solubility:
- Temperature: Generally increases for solids, decreases for gases
- Pressure: Significant effect on gases (Henry's law)
- Nature of solute and solvent: "Like dissolves like"

3. Colligative Properties

📊 Definition:
Properties that depend on the number of solute particles, not their identity.

🧪 Four Colligative Properties:
1. Relative lowering of vapor pressure (Δp)
2. Elevation of boiling point (ΔTb)
3. Depression of freezing point (ΔTf)
4. Osmotic pressure (π)

📊 Relative Lowering of Vapor Pressure (Raoult's Law):
For volatile solute: p = x₁p₁° + x₂p₂°
For non-volatile solute: p = x₁p₁°
Δp = p₁° - p = x₂p₁°

📊 Elevation of Boiling Point:
ΔTb = Kb × m × i
Where:
- Kb = Boiling point elevation constant
- m = Molality
- i = Van't Hoff factor

📊 Depression of Freezing Point:
ΔTf = Kf × m × i
Where:
- Kf = Freezing point depression constant
- m = Molality
- i = Van't Hoff factor

📊 Osmotic Pressure:
π = iMRT
Where:
- i = Van't Hoff factor
- M = Molarity
- R = Gas constant (0.0821 L·atm·K⁻¹·mol⁻¹)
- T = Temperature (Kelvin)

4. Van’t Hoff Factor

🔢 Definition:
Ratio of actual colligative property to theoretical colligative property

i = Actual number of particles/Theoretical number of particles

📊 Values:
- Non-electrolytes: i = 1 (glucose, urea)
- Strong electrolytes: i ≈ number of ions (NaCl: i = 2, CaCl₂: i = 3)
- Weak electrolytes: 1 < i < number of ions

📊 Association and Dissociation:
- For dissociation: i > 1
- For association: i < 1
- For non-electrolytes: i = 1

5. Crystal Systems and Unit Cells

🔷 Seven Crystal Systems:
1. Cubic: a = b = c, α = β = γ = 90°
2. Tetragonal: a = b ≠ c, α = β = γ = 90°
3. Orthorhombic: a ≠ b ≠ c, α = β = γ = 90°
4. Hexagonal: a = b ≠ c, α = β = 90°, γ = 120°
5. Rhombohedral: a = b = c, α = β = γ ≠ 90°
6. Monoclinic: a ≠ b ≠ c, α = γ = 90°, β ≠ 90°
7. Triclinic: a ≠ b ≠ c, α ≠ β ≠ γ ≠ 90°

📊 Unit Cell Types:
1. Primitive (P): Lattice points at corners only
2. Body-centered (I): Corners + body center
3. Face-centered (F): Corners + face centers
4. End-centered (C): Corners + center of two opposite faces

6. Crystal Lattice Calculations

🔷 Atoms per Unit Cell:
- Simple cubic (SC): 1 atom per unit cell
- Body-centered cubic (BCC): 2 atoms per unit cell
- Face-centered cubic (FCC): 4 atoms per unit cell

📊 Packing Efficiency:
- SC: 52.4%
- BCC: 68%
- FCC: 74%
- HCP: 74%

📊 Coordination Number:
- SC: 6
- BCC: 8
- FCC: 12
- HCP: 12

📊 Density Calculations:
ρ = (Z × M)/(a³ × NA)
Where:
- ρ = Density
- Z = Number of atoms per unit cell
- M = Molar mass
- a = Edge length
- NA = Avogadro's number

7. Imperfections in Solids

🔷 Point Defects:
1. Vacancy defect: Missing atom from lattice site
2. Interstitial defect: Extra atom in interstitial site
3. Frenkel defect: Ion displaced to interstitial site
4. Schottky defect: Pair of vacancies

📊 Stoichiometric Defects:
- Frenkel: Shown by compounds with large size difference
- Schottky: Shown by ionic compounds with similar cation and anion sizes

📊 Non-stoichiometric Defects:
- Metal deficiency: Lower metal ratio than ideal
- Metal excess: Higher metal ratio than ideal

8. Electrical and Magnetic Properties

⚡ Electrical Properties:
1. Conductors: Low resistivity (10⁻⁶ to 10⁻⁴ Ω·cm)
2. Semiconductors: Medium resistivity (10⁻⁴ to 10¹⁰ Ω·cm)
3. Insulators: High resistivity (10¹¹ to 10¹⁹ Ω·cm)

🧲 Magnetic Properties:
1. Diamagnetic: Weak repulsion by magnetic field
2. Paramagnetic: Weak attraction by magnetic field
3. Ferromagnetic: Strong attraction by magnetic field
4. Antiferromagnetic: Antiparallel alignment of spins
5. Ferrimagnetic: Unequal antiparallel alignment

📈 Year-wise Question Analysis

Recent NEET Questions (2019-2024)

2024 NEET Questions

📝 Question 1: Boiling Point Elevation
Calculate the boiling point of solution containing 18 g glucose (C₆H₁₂O₆) in 100 g water. (Kb for water = 0.52 K·kg·mol⁻¹)

Solution:
Molar mass of glucose = 180 g/mol
Moles of glucose = 18/180 = 0.1 mol
Mass of water = 100 g = 0.1 kg
Molality (m) = 0.1/0.1 = 1 mol/kg

For glucose (non-electrolyte): i = 1
ΔTb = Kb × m × i = 0.52 × 1 × 1 = 0.52 K
Boiling point of water = 100°C
Boiling point of solution = 100 + 0.52 = 100.52°C

Answer: 100.52°C

📝 Question 2: Unit Cell Calculation
Silver crystallizes in FCC structure with edge length 4.07 × 10⁻⁸ cm. Calculate its density. (Ag = 108 g/mol)

Solution:
For FCC: Z = 4 atoms per unit cell
Edge length a = 4.07 × 10⁻⁸ cm
Volume a³ = (4.07 × 10⁻⁸)³ = 6.74 × 10⁻²³ cm³

Density ρ = (Z × M)/(a³ × NA)
ρ = (4 × 108)/(6.74 × 10⁻²³ × 6.022 × 10²³)
ρ = 432/(4.06) = 10.64 g/cm³

Answer: 10.64 g/cm³

2023 NEET Questions

📝 Question 1: Freezing Point Depression
A solution containing 5.85 g NaCl in 100 g water freezes at -1.86°C. Calculate van't Hoff factor. (Kf for water = 1.86 K·kg·mol⁻¹)

Solution:
Molar mass of NaCl = 58.5 g/mol
Moles of NaCl = 5.85/58.5 = 0.1 mol
Mass of water = 100 g = 0.1 kg
Molality (m) = 0.1/0.1 = 1 mol/kg

Observed ΔTf = 1.86°C
Theoretical ΔTf = Kf × m = 1.86 × 1 = 1.86°C

Van't Hoff factor i = Observed/Theoretical = 1.86/1.86 = 1

Answer: i = 1

📝 Question 2: Crystal Structure
Which of the following has highest packing efficiency?
(A) Simple cubic
(B) Body-centered cubic
(C) Face-centered cubic
(D) All have same packing efficiency

Solution:
Packing efficiency:
- Simple cubic: 52.4%
- Body-centered cubic: 68%
- Face-centered cubic: 74%
- Hexagonal close-packed: 74%

FCC has highest packing efficiency at 74%

Answer: (C) Face-centered cubic

2022 NEET Questions

📝 Question 1: Osmotic Pressure
Calculate osmotic pressure of solution containing 6 g urea in 500 mL at 27°C. (R = 0.0821 L·atm·K⁻¹·mol⁻¹)

Solution:
Molar mass of urea = 60 g/mol
Moles of urea = 6/60 = 0.1 mol
Volume = 500 mL = 0.5 L
Molarity M = 0.1/0.5 = 0.2 mol/L
Temperature T = 27°C = 300 K

For urea (non-electrolyte): i = 1
π = iMRT = 1 × 0.2 × 0.0821 × 300 = 4.93 atm

Answer: 4.93 atm

📝 Question 2: Henry's Law
The solubility of O₂ in water at 1 atm pressure is 0.03 mol/L. What will be solubility at 3 atm pressure?

Solution:
According to Henry's law: x ∝ p
Solubility at 1 atm = 0.03 mol/L
Solubility at 3 atm = 3 × 0.03 = 0.09 mol/L

Answer: 0.09 mol/L

🎯 Common Question Patterns

Pattern 1: Colligative Properties Calculations

📊 Typical Structure:
- Given: Mass of solute, mass/volume of solvent, constants
- Required: Calculate boiling/freezing point or osmotic pressure
- Method: Apply colligative property formulas

🔢 Steps:
1. Calculate moles of solute
2. Determine molality or molarity
3. Identify van't Hoff factor
4. Apply appropriate formula
5. Calculate property change

Pattern 2: Crystal Structure Calculations

📊 Typical Structure:
- Given: Crystal structure, edge length, molar mass
- Required: Calculate density or related properties
- Method: Apply unit cell formulas

🔢 Steps:
1. Identify crystal type (SC, BCC, FCC)
2. Determine Z (atoms per unit cell)
3. Calculate unit cell volume
4. Apply density formula
5. Solve for unknown quantity

Pattern 3: Solubility and Concentration

📊 Typical Structure:
- Given: Solubility data or concentration information
- Required: Calculate related properties
- Method: Apply solubility principles and concentration formulas

🔢 Steps:
1. Identify type of solution
2. Apply appropriate concentration formula
3. Use Henry's law if gas solubility
4. Calculate required quantity

⚠️ Common Mistakes and Solutions

Mistake 1: Colligative Property Formulas

❌ Common Error:
- Using wrong constant (Kf vs Kb)
- Incorrect van't Hoff factor
- Unit conversion errors

✅ Correct Approach:
- Use Kf for freezing point, Kb for boiling point
- Determine correct i value based on solute type
- Convert units consistently (g→kg, mL→L)

Mistake 2: Crystal Structure Calculations

❌ Common Error:
- Wrong Z value for unit cell
- Incorrect volume calculation
- Unit conversion mistakes

✅ Correct Approach:
- Memorize Z values: SC=1, BCC=2, FCC=4
- Calculate volume correctly (a³)
- Use consistent units (cm³)

Mistake 3: Henry’s Law Applications

❌ Common Error:
- Wrong pressure units
- Incomplete solubility data
- Temperature effects ignored

✅ Correct Approach:
- Use pressure in same units as KH constant
- Ensure complete solubility information
- Note temperature dependence

🔧 Problem-Solving Strategies

Colligative Properties Problems

📝 Systematic Approach:
1. Identify type of colligative property
2. Calculate moles of solute
3. Determine concentration (molality or molarity)
4. Find van't Hoff factor
5. Apply appropriate formula
6. Calculate final answer

Crystal Structure Problems

📝 Step-by-Step Method:
1. Identify crystal system and unit cell type
2. Determine Z value
3. Calculate unit cell volume
4. Apply density or related formula
5. Solve for unknown quantity

Solution Problems

📝 Problem-Solving Method:
1. Identify type of solution
2. Determine appropriate concentration term
3. Apply relevant laws (Raoult's, Henry's)
4. Calculate required quantity

📚 Practice Questions by Difficulty

Easy Level (Foundation Building)

📝 Practice Set 1:
1. Define colligative properties.
2. What is the van't Hoff factor for glucose?
3. How many atoms are in BCC unit cell?
4. State Henry's law.
5. What is osmotic pressure?

🎯 Expected Time: 30-45 seconds per question
💡 Focus: Basic concept recall

Medium Level (Concept Application)

📝 Practice Set 2:
1. Calculate boiling point of 1 M NaCl solution (Kb = 0.52).
2. Find density of NaCl (FCC, a = 5.64 Å, M = 58.5).
3. Calculate osmotic pressure of 0.1 M sucrose at 300 K.
4. Determine coordination number of FCC structure.
5. Calculate freezing point of 0.5 M glucose solution (Kf = 1.86).

🎯 Expected Time: 1.5-2.5 minutes per question
💡 Focus: Formula application

Hard Level (Advanced Problems)

📝 Practice Set 3:
1. A solution freezes at -0.93°C containing 3.42 g BaCl₂ in 100 g water. Find van't Hoff factor.
2. Calculate radius of atom in FCC structure with density 10.5 g/cm³ and M = 108.
3. At what pressure will O₂ solubility be 0.06 mol/L if solubility at 1 atm is 0.03 mol/L?
4. Find mass of NaCl required to make solution boil at 101°C (mass of water = 100 g).
5. Calculate edge length of BCC unit cell with density 8.55 g/cm³ and M = 55.85.

🎯 Expected Time: 2-3 minutes per question
💡 Focus: Complex multi-step problems

📈 Performance Analysis

Success Rate by Question Type

📊 Success Rate Analysis:
- Basic definitions: 85% success rate
- Simple concentration calculations: 75% success rate
- Colligative properties: 65% success rate
- Crystal structure calculations: 60% success rate
- Complex problems: 45% success rate

Time Management Analysis

⏱️ Average Time Taken:
- Easy questions: 30-45 seconds
- Medium questions: 1.5-2.5 minutes
- Hard questions: 2-3 minutes
- Very hard questions: 3-4 minutes

🎯 Recommended Time Allocation:
- Total 20-25 minutes for all questions
- Maximum 2.5 minutes per question
- Skip and return if taking longer

Common Error Analysis

📊 Error Categories:
1. Formula application errors: 30% of mistakes
2. Unit conversion errors: 25% of mistakes
3. Mathematical calculation errors: 20% of mistakes
4. Conceptual understanding errors: 15% of mistakes
5. Van't Hoff factor errors: 10% of mistakes

🔧 Improvement Strategies:
- Master all formulas thoroughly
- Practice unit conversions
- Improve calculation skills
- Strengthen conceptual understanding
- Learn van't Hoff factor patterns

🎮 Interactive Learning Features

Formula Quick Reference

📋 Essential Formulas:
- ΔTb = Kb × m × i
- ΔTf = Kf × m × i
- π = iMRT
- ρ = (Z × M)/(a³ × NA)
- p = KH × x (Henry's law)
- Molarity = moles/volume (L)
- Molality = moles/mass (kg)

Crystal Structure Data

🔷 Unit Cell Information:
SC: Z=1, CN=6, PE=52.4%
BCC: Z=2, CN=8, PE=68%
FCC: Z=4, CN=12, PE=74%
HCP: Z=2, CN=12, PE=74%

CN = Coordination Number
PE = Packing Efficiency

Van’t Hoff Factors

🔢 Common Values:
- Non-electrolytes: i = 1
- NaCl, KCl: i = 2
- CaCl₂, MgCl₂: i = 3
- AlCl₃: i = 4
- Weak electrolytes: 1 < i < n

🔄 Regular Practice Schedule

Daily Practice Routine

📅 30-Minute Daily Session:
- 15 minutes: Colligative properties
- 15 minutes: Crystal structure

📊 Weekly Progress:
- Day 1-2: Basic solutions and concentration
- Day 3-4: Colligative properties
- Day 5-6: Crystal structure and unit cells
- Day 7: Mixed practice and revision

Monthly Assessment

📈 Monthly Goals:
- Master all colligative property formulas
- Complete 40+ crystal structure problems
- Practice 30+ colligative calculations
- Learn all crystal systems
- Achieve 75% accuracy in medium problems

✅ Self-Assessment Checklist

Concept Mastery Checklist

☐ Types of solutions and concentration terms
☐ Solubility and Henry's law
☐ Colligative properties and their formulas
☐ Van't Hoff factor and its applications
☐ Raoult's law and vapor pressure
☐ Crystal systems and unit cells
☐ Unit cell calculations (density, edge length)
☐ Packing efficiency and coordination number
☐ Imperfections in solids
☐ Electrical and magnetic properties

Problem-Solving Skills

☐ Can calculate concentration terms
☐ Can apply colligative property formulas
☐ Can determine van't Hoff factors
☐ Can solve crystal structure problems
☐ Can calculate density from unit cell data
☐ Can apply Henry's law
☐ Can handle multi-step calculations
☐ Can complete within time limit

📊 Additional Resources

Important Constants

🔢 Key Values:
- R = 0.0821 L·atm·K⁻¹·mol⁻¹
- NA = 6.022 × 10²³ mol⁻¹
- 1 Å = 10⁻⁸ cm
- Kb (water) = 0.52 K·kg·mol⁻¹
- Kf (water) = 1.86 K·kg·mol⁻¹

Crystal Systems Summary

🔷 Quick Reference:
Cubic: a=b=c, α=β=γ=90° (SC, BCC, FCC)
Tetragonal: a=b≠c, α=β=γ=90°
Orthorhombic: a≠b≠c, α=β=γ=90°
Hexagonal: a=b≠c, α=β=90°, γ=120°

Master solutions and solid state with this comprehensive NEET PYQ collection! Build strong numerical skills, understand crystal structures, and excel in Physical Chemistry! 🔷

Every solution property understood and crystal structure visualized strengthens your foundation in Chemistry! Begin your solid-state exploration today! 🏗️