Engineering Chemistry
Atomic Structure: Includes fundamental particles, Bohr's theory, orbits/orbitals, Pauli's exclusion principle, Hund's rule, Aufbau principle, and nuclear stability
. Electrochemistry: Covers Arrhenius theories, electrolysis, Faraday's laws, conductivity, and solubility products
. Water Treatment: Focuses on purification processes (filtration, sterilization), causes and removal of water hardness, and the application of pH/pOH values
. Materials & Metallurgy: Details the extraction of iron, types of carbon steel, heat treatment, properties of metals, and the preparation/application of various alloys
. Corrosion: Explains atmospheric and electrochemical corrosion mechanisms, along with protective metallic and non-metallic coatings (paints and varnishes)
. Non-Metallic Materials: Encompasses the formation and properties of plastics, natural and synthetic rubbers, insulating materials, glass, and cement
. Pollution & Lubricants: Covers the types and control of air, water, and land pollution, as well as the functions and selection of lubricants
.
1. Introduction of Atom
- Atom is the smallest particle of an element which retains its chemical properties.
-
It consists of:
- Protons (+ve charge)
- Neutrons (neutral)
- Electrons (-ve charge)
2. Fundamental Particles of Atom
| Particle | Symbol | Charge | Mass (amu) | Location |
|---|---|---|---|---|
| Proton | p⁺ | +1 | 1 | Nucleus |
| Neutron | n⁰ | 0 | 1 | Nucleus |
| Electron | e⁻ | -1 | 1/1837 | Extra nuclear shell |
Important Points
- Proton number = Atomic number (Z)
- Protons + Neutrons = Mass number (A)
3. Atomic Number and Mass Number
Atomic Number (Z)
Number of protons present in an atom.
Example:
Carbon (C)
- Proton = 6
- Atomic number = 6
Mass Number (A)
Total number of protons and neutrons.
Formula:
Example:
Chlorine atom
- Protons = 17
- Neutrons = 18
Mass number
4. Simple Numerical Problems
Formula
Neutrons = Mass Number – Atomic Number
Example
Atomic number = 11
Mass number = 23
Neutrons
Answer: 12 neutrons
5. Isotopes and Isobars
Isotopes
Atoms having same atomic number but different mass number.
Examples
Hydrogen isotopes:
- Protium (¹H)
- Deuterium (²H)
- Tritium (³H)
Characteristics
- Same chemical properties.
- Different physical properties.
Isobars
Atoms having same mass number but different atomic numbers.
Example
| Element | Atomic Number | Mass Number |
|---|---|---|
| Argon | 18 | 40 |
| Calcium | 20 | 40 |
Difference Between Isotopes and Isobars
| Isotopes | Isobars |
|---|---|
| Same atomic number | Same mass number |
| Different mass number | Different atomic number |
| Example: ¹H,²H,³H | Example: Ar-40 and Ca-40 |
6. Bohr's Theory of Hydrogen Atom
Postulates
- Electrons revolve around nucleus in fixed circular paths called shells.
- These shells are K, L, M, N.
- Electron does not lose energy while revolving.
- Energy is emitted or absorbed when electron jumps from one shell to another.
Energy Formula
7. Modern Atomic Structure
According to modern theory:
- Electrons move in three-dimensional regions called orbitals.
- Exact position of electron cannot be determined.
- Based on quantum mechanics.
8. Orbit and Orbital
Orbit
- Fixed circular path around nucleus.
- Two-dimensional.
- Given by Bohr model.
Orbital
- Region of maximum probability of finding electron.
- Three-dimensional.
- Given by quantum theory.
Shapes of Orbitals
- s orbital → Spherical
- p orbital → Dumbbell
- d orbital → Double dumbbell
- f orbital → Complex
9. Sub-Energy Levels
| Shell | Sub-shell |
|---|---|
| K (n=1) | s |
| L (n=2) | s,p |
| M (n=3) | s,p,d |
| N (n=4) | s,p,d,f |
Capacity
- s = 2 electrons
- p = 6 electrons
- d = 10 electrons
- f = 14 electrons
10. Pauli's Exclusion Principle
Statement:
"No two electrons in an atom can have the same set of four quantum numbers."
Short Form
One orbital can accommodate a maximum of two electrons with opposite spins.
↑↓
11. Hund's Rule
Statement:
Electrons occupy empty orbitals singly before pairing.
Example:
p orbitals
↑ ↑ ↑
then pairing starts
↑↓ ↑↓ ↑
12. Aufbau Principle (2 ≤ Z ≤ 30)
Order of Filling
1s
2s
2p
3s
3p
4s
3d
4p
Electronic Configuration Examples
Sodium (Z = 11)
1s² 2s² 2p⁶ 3s¹
Calcium (Z = 20)
1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
Zinc (Z = 30)
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰
13. Variable Valency
Some elements show more than one valency.
Examples
| Element | Valencies |
|---|---|
| Iron (Fe) | 2,3 |
| Copper (Cu) | 1,2 |
| Tin (Sn) | 2,4 |
| Lead (Pb) | 2,4 |
Ferrous and Ferric Compounds
Ferrous Compound (Fe²⁺)
- FeCl₂
- FeSO₄
Ferric Compound (Fe³⁺)
- FeCl₃
- Fe₂O₃
14. Nuclear Stability
A nucleus is stable when attractive nuclear force balances repulsive force between protons.
Factors Affecting Stability
- Neutron-proton ratio.
- Binding energy per nucleon.
- Nuclear force.
15. Mass Defect
Difference between actual mass of nucleus and sum of masses of protons and neutrons.
Formula
where
- Z = Number of protons
- N = Number of neutrons
- M = Actual nuclear mass
16. Binding Energy
Energy required to separate nucleus into individual nucleons.
Einstein Equation
where
c = 3×10⁸ m/s
Important Numericals
Q1. Atomic number = 19 and Mass number = 39. Find neutrons.
Solution:
Neutrons = 39 – 19 = 20
Answer = 20 neutrons
Q2. Find protons in Aluminium (Z = 13).
Answer = 13 protons
Q3. Find mass number if proton = 17 and neutron = 18.
Mass number = 17 + 18 = 35
Answer = 35
Most Important Viva Questions (D2D Jharkhand)
- What is an atom?
- Define atomic number and mass number.
- What are isotopes? Give examples.
- Differentiate between isotopes and isobars.
- State Bohr's postulates.
- Distinguish between orbit and orbital.
- State Pauli exclusion principle.
- State Hund's rule.
- State Aufbau principle.
- What is variable valency?
- Define mass defect.
- Define binding energy.
- Write Einstein's equation.
- What is nuclear stability?
These notes are short, detailed, and according to D2D Jharkhand Polytechnic syllabus, suitable for one-day revision and examination preparation.
1. Arrhenius Theory of Ionization
Definition
According to Arrhenius, an electrolyte dissociates into positive and negative ions when dissolved in water or in molten state.
Example
NaCl → Na⁺ + Cl⁻
HCl → H⁺ + Cl⁻
Electrolyte
Substance which conducts electricity in aqueous solution or molten state.
Types of Electrolytes
(a) Strong Electrolytes
Completely ionize in solution.
Examples
HCl
H₂SO₄
NaOH
NaCl
(b) Weak Electrolytes
Partially ionize in solution.
Examples
CH₃COOH
NH₄OH
H₂CO₃
2. Degree of Ionization (α)
Definition
Fraction of total molecules that ionize in solution.
Formula
Values
α = 1 → Complete ionization (Strong electrolyte)
α < 1 → Partial ionization (Weak electrolyte)
3. Electrochemical Series
Definition
Arrangement of elements according to their standard electrode potentials.
Important Series
K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag > Au
Applications
1. Predicts displacement reaction
Zn + CuSO₄ → ZnSO₄ + Cu
(Zn is above Cu, hence zinc displaces copper.)
2. Predicts reducing power
More electropositive metals are stronger reducing agents.
3. Predicts reactivity of metals
Potassium is more reactive than copper.
4. Selection of metal for electroplating and extraction.
4. Electrolysis of CuSO₄ Solution
(A) Using Platinum Electrodes (Inert)
Cathode (-)
Cu²⁺ + 2e⁻ → Cu
Copper deposits at cathode.
Anode (+)
2H₂O → O₂ + 4H⁺ + 4e⁻
Oxygen gas is evolved.
Observation
Copper deposited on cathode.
Oxygen gas liberated at anode.
Blue colour gradually fades.
(B) Using Copper Electrodes
Cathode (-)
Cu²⁺ + 2e⁻ → Cu
Copper deposited.
Anode (+)
Cu → Cu²⁺ + 2e⁻
Copper dissolves from anode.
Observation
Mass of anode decreases.
Mass of cathode increases.
Concentration of CuSO₄ remains constant.
5. Applications of Electrolysis
Electroplating
Definition
Deposition of one metal over another by electrolysis.
Examples
Chromium plating on car parts.
Silver plating on utensils.
Gold plating on jewellery.
Uses
Prevent corrosion.
Improve appearance.
Increase hardness.
Electrorefining
Definition
Purification of impure metals by electrolysis.
Example
Purification of copper.
Arrangement
Anode → Impure copper
Cathode → Pure copper sheet
Electrolyte → CuSO₄ solution
6. Faraday's Laws of Electrolysis
First Law
Statement
Mass of substance deposited is directly proportional to quantity of electricity passed.
Formula
or
where
W = Mass deposited (g)
Z = Electrochemical equivalent
I = Current (A)
t = Time (s)
Second Law
Statement
When same quantity of electricity passes through different electrolytes, masses deposited are proportional to their equivalent weights.
Formula
where
E = Equivalent weight
Important Numerical
Example
Current = 2 A
Time = 30 min = 1800 s
Electrochemical equivalent of Cu = 0.00033 g/C
Find mass deposited.
Solution
W = ZIt
= 0.00033 × 2 × 1800
= 1.188 g
Answer = 1.188 g
7. Conductivity of an Electrolyte
Definition
Ability of electrolyte solution to conduct electricity.
Unit
S cm⁻¹ or Ω⁻¹ cm⁻¹
Factors Affecting Conductivity
Concentration
Temperature
Nature of electrolyte
Mobility of ions
8. Specific Conductivity (κ)
Definition
Conductance of a solution enclosed between electrodes 1 cm apart having area 1 cm².
Formula
where
R = Resistance
l = Distance between electrodes
A = Area of electrodes
Unit
Ω⁻¹ cm⁻¹or S cm⁻¹
9. Solubility Product (Ksp)
Definition
Product of molar concentrations of ions in a saturated solution.
Example
AgCl ⇌ Ag⁺ + Cl⁻
Expression
Importance
Predicts precipitation.
Determines solubility of salts.
10. Common Ion Effect
Definition
Suppression of ionization of a weak electrolyte by adding a strong electrolyte having a common ion.
Example
CH₃COOH ⇌ H⁺ + CH₃COO⁻
Adding CH₃COONa increases CH₃COO⁻ ions and decreases ionization of CH₃COOH.
Flow Chart for Revision
Electrochemistry
↓
Arrhenius Theory
↓
Strong & Weak Electrolytes
↓
Degree of Ionization
↓
Electrochemical Series
↓
Electrolysis of CuSO4
(Platinum & Copper Electrodes)
↓
Applications
(Electroplating & Electrorefining)
↓
Faraday's Laws
↓
Conductivity
↓
Specific Conductivity
↓
Solubility Product
↓
Common Ion Effect
Most Important Viva Questions (D2D Jharkhand)
Q1. State Arrhenius theory of ionization.
Ans: Electrolytes dissociate into ions in aqueous solution or molten state.
Q2. Differentiate between strong and weak electrolytes.
Ans: Strong electrolytes ionize completely, while weak electrolytes ionize partially.
Q3. What is degree of ionization?
Ans: Ratio of ionized molecules to total molecules.
Q4. State Faraday's first law.
Ans: Mass deposited is directly proportional to quantity of electricity passed.
Q5. Write the equation of Faraday's first law.
Ans: W = ZIt.
Q6. What is electroplating?
Ans: Deposition of one metal over another by electrolysis.
Q7. What is electrorefining?
Ans: Purification of metals by electrolysis.
Q8. Define specific conductivity.
Ans: Conductance of a solution kept between electrodes 1 cm apart and 1 cm² in area.
Q9. What is solubility product?
Ans: Product of ionic concentrations in a saturated solution.
Q10. What is common ion effect?
Ans: Suppression of ionization of a weak electrolyte due to addition of a common ion.
These notes are prepared in short and detailed form according to D2D Jharkhand Polytechnic syllabus, suitable for quick revision, viva, and semester examination.
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