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B.Sc. 1st Year Chemistry Notes

Basic Chemistry I | CHE-101 | Tribhuvan University

Course Information

University: Tribhuvan University

Course: Basic Chemistry I

Course No.: CHE-101

Full Marks: 100

Pass Marks: 35

Nature: Theory

Note: Practical Chemistry I (CHE-102) is not included on this page. This page is focused on the CHE-101 theory course.

About These Chemistry Notes

These notes are arranged according to the CHE-101 topics listed below. The material covers inorganic chemistry, organic chemistry and physical chemistry.

The aim is to explain the chemical idea before asking the student to memorize a definition, equation or reaction. Important equations are followed by an explanation of what the terms mean and, where applicable, how the equation is used in a numerical problem.

Organic chemistry sections focus on reaction conditions, intermediates, mechanism and product formation rather than simply listing reactions. Physical chemistry sections give attention to units, formula selection, calculation steps and interpretation of the final answer.

Inorganic chemistry sections emphasize trends, structures, bonding, acid-base behaviour and the reason behind observed properties.

CHE-101 Topic Index

Use the links below to move directly to a chapter.

Inorganic Chemistry Organic Chemistry Physical Chemistry Final Revision

Core Study Guide

Before opening individual chapters, the following points help connect some of the major ideas in CHE-101.

Atomic Structure and Periodicity

The modern description of an atom uses orbitals rather than fixed circular electron paths. The four quantum numbers describe the state of an electron.

The principal quantum number n indicates the main energy level. The azimuthal quantum number l identifies the subshell. The magnetic quantum number describes the orientation of an orbital and the spin quantum number describes electron spin.

λ = h / mv

The de Broglie equation relates wavelength to momentum. A particle with greater momentum has a shorter wavelength.

Δx × Δp ≥ h / 4π

The uncertainty principle does not mean that measurement instruments are simply inaccurate. It expresses a fundamental limit on simultaneously specifying the position and momentum of a microscopic particle.

Across a period, atomic radius generally decreases while ionization energy and electronegativity generally increase. Down a group, additional electron shells increase atomic size and shielding.

Chemical Bonding

Ionic bonding results from electrostatic attraction between oppositely charged ions. Covalent bonding involves sharing of electron pairs. The properties of the resulting substance depend on the type of bonding and the structure produced.

Lattice energy is related to the strength of attraction between ions in an ionic solid. Higher ionic charge and smaller ionic size generally increase the magnitude of this attraction.

Fajan's rule is useful when discussing covalent character in ionic compounds. A small, highly charged cation has greater polarizing power, while a large anion is more easily polarized.

For covalent molecules, VSEPR theory is useful for predicting molecular shape. Hybridization provides a convenient description of orbital arrangement, while molecular orbital theory explains bonding and magnetic behaviour in greater detail.

Organic Reaction Mechanisms

Organic reactions become easier to understand when the electron-rich and electron-poor parts of the reacting molecules are identified first.

A nucleophile donates an electron pair. An electrophile accepts an electron pair. A leaving group departs with the electron pair that formed the original bond.

In an SN2 reaction, substitution occurs in one concerted step. The nucleophile attacks from the side opposite the leaving group, producing inversion at a suitable chiral centre.

Rate of SN2 = k[alkyl halide][nucleophile]

In an SN1 reaction, the substrate first forms a carbocation. The slow ionization step means that the rate depends primarily on the concentration of the substrate.

Rate of SN1 = k[alkyl halide]
Common mistake: Do not decide between SN1 and SN2 only by memorizing substrate names. Consider substrate structure, nucleophile, solvent, leaving group and steric hindrance together.

Gases, Equilibrium and Solutions

The ideal gas equation is one of the most frequently used relationships in physical chemistry.

PV = nRT

Real gases deviate from ideal behaviour because gas molecules occupy space and attract one another. The van der Waals equation introduces corrections for both effects.

(P + an2/V2)(V − nb) = nRT

Chemical equilibrium is dynamic. The forward and reverse reactions continue to occur, but their rates are equal at equilibrium.

For a weak acid buffer, the Henderson-Hasselbalch relationship is useful for estimating the pH.

pH = pKa + log([A−] / [HA])
Common calculation mistake: Always check whether concentration values are expressed in the units required by the equation. Also check whether the logarithm should contain a ratio of concentrations rather than one concentration alone.

Kinetics and Thermodynamics

Reaction kinetics deals with the speed of a reaction and the factors that affect that speed. Thermodynamics deals with energy changes and whether a process is thermodynamically favourable.

For a first-order reaction, the half-life is independent of the initial concentration.

t1/2 = 0.693 / k

The Arrhenius equation relates the rate constant to temperature and activation energy.

k = A e−Ea/RT

Gibbs free energy combines enthalpy and entropy changes.

ΔG = ΔH − TΔS
  • ΔG < 0: forward process is thermodynamically favourable under the stated conditions.
  • ΔG = 0: system is at equilibrium.
  • ΔG > 0: forward process is not spontaneous under the stated conditions.

Group A: Inorganic Chemistry

These chapters cover atomic structure, nuclear chemistry, periodic properties, chemical bonding, acid-base chemistry and the basic principles used in chemical analysis.

Chapter 1

Atomic Structure

Bohr's theory and its limitations, wave mechanical model, matter waves, de Broglie equation, Heisenberg uncertainty principle, Schrödinger wave equation, physical significance of the wave function, probability density, radial and angular wave functions, radial distribution curves, orbital shapes, nodal planes, quantum numbers and energy levels.

Study point: When explaining an orbital, distinguish its shape from its orientation and distinguish an orbital from an electron shell.
Chapter 2

Multi-electron System

Pauli exclusion principle, Hund's rule of maximum multiplicity, energy-level diagrams and the electronic arrangements of multi-electron atoms, including the stability associated with completely filled and half-filled subshells.

Common mistake: Do not confuse Hund's rule with the Pauli exclusion principle. They describe different restrictions on electron arrangement.
Chapter 3

Nuclear Chemistry

Composition and stability of the nucleus, mass defect, binding energy, radioactivity, half-life, nuclear reactions, group displacement law, radioactive series and applications of nuclear chemistry.

Numerical point: In half-life calculations, identify the number of half-lives first. The amount remaining after n half-lives is:
N = N0(1/2)n
Chapter 4

Periodic Classification and Periodic Properties

Long-form periodic table, IUPAC classification, periodicity, s-, p-, d- and f-block elements, atomic, ionic and covalent radii, ionization potential, shielding effect, electronegativity, electronegativity scales and electron affinity.

How to answer a trend question: State the trend first, then give the reason using nuclear charge, shielding and distance of the outer electron.
Chapter 5

Chemical Bonding

Ionic bonding, crystal packing, radius ratio, lattice energy, Born equation, Born-Haber cycle, Fajan's rule, polarizing power, polarizability, bond moment, dipole moment and ionic character; covalent bonding, hybridization, VSEPR theory, molecular orbital theory, hydrogen bonding and metallic bonding.

Common mistake: Molecular shape and electron-pair geometry are not always identical. Lone pairs occupy space and can change the observed molecular shape.
Chapter 6

Acids and Bases

Lewis acid-base concept, hard and soft acids and bases, HSAB principle and its applications, relative acid and base strength, and the effects of substituents and solvents.

Useful comparison: When comparing acid strength, consider factors such as charge, atom size, electronegativity, resonance, inductive effect and solvent effects rather than relying on one rule for every case.
Chapter 7

Principles of Qualitative and Quantitative Analysis

Solubility product, common-ion effect and their application in group separation, together with the basic principles of gravimetric and volumetric analysis.

Laboratory connection: Qualitative analysis asks which species are present, whereas quantitative analysis asks how much of a species is present. Keeping these two purposes separate helps when selecting an analytical method.

Group B: Organic Chemistry

These chapters focus on organic structure, electronic effects, stereochemistry and the reactions of important hydrocarbon and functional-group classes.

Chapter 8

Structure and Properties of Organic Compounds

Atomic, molecular and hybrid orbitals, polarity of bonds, melting point, acid-base behaviour, dipole-dipole interactions, hydrogen bonding, inductive effect, electromeric effect, resonance, mesomeric effect, hyperconjugation, steric effect and IUPAC nomenclature.

Common mistake: Resonance structures are not separate compounds that rapidly change into one another. They are contributing structures used to represent electron delocalization.
Chapter 9

Alkanes and Free-Radical Reactions

Activation energy, reaction progress and energy profiles, Fischer and Newman projections, free rotation, n-butane conformation, preparation and sources of alkanes, halogenation, free-radical mechanism, orientation, reactivity and selectivity, combustion and pyrolysis.

Mechanism order: For a free-radical chain reaction, identify initiation, propagation and termination separately.
Chapter 10

Stereochemistry

Structural isomerism and stereoisomerism, optical activity, polarimeter, specific rotation, enantiomers, chirality, chiral centres, racemic modification, resolution, configuration, R and S notation, diastereomers, meso compounds and geometrical isomerism.

[α] = αobserved / (l × c)

The exact form of the specific-rotation calculation depends on the units used for path length and concentration. Always check the convention specified in the question.

Chapter 11

Alkyl Halides: Nucleophilic Substitution

Homolytic and heterolytic fission, structure and classification of alkyl halides, preparation, nucleophiles and leaving groups, SN2 mechanism and kinetics, inversion of configuration, SN1 mechanism, carbocations, stereochemistry, rearrangement and factors affecting SN1 and SN2 reactions.

Quick Check

Why does SN2 reaction become slower when steric hindrance around the reacting carbon increases?
SN2 requires direct backside attack by the nucleophile. Greater crowding around the carbon makes this approach more difficult.
Chapter 12

Alcohols and Ethers

Nomenclature, structure, physical properties, industrial sources, fermentation, ethanol, preparation and reactions of alcohols, acidity, reaction with hydrogen halides, sulphonate formation, oxidation, preparation of ethers, Williamson synthesis and reactions of ethers.

Reaction interpretation: When studying oxidation of alcohols, first identify whether the alcohol is primary, secondary or tertiary. The expected oxidation product depends strongly on this classification.
Chapter 13

Alkenes

Preparation and physical properties, dehydrohalogenation, E1 and E2 reactions, electrophilic addition, hydrogenation, hydrogen-halide addition, peroxide effect, hydration, halogenation, halohydrin formation, oxymercuration-demercuration, hydroboration-oxidation, hydroxylation, ozonolysis and polymer formation.

Common mistake: Do not treat every alkene addition as having the same orientation. Check the reagent and mechanism before deciding which carbon receives which group.
Chapter 14

Alkynes

Structure of acetylene, physical properties, industrial source, preparation of alkynes, reduction to alkenes, electrophilic addition, hydration, acidity of alkynes, metal acetylides and analysis of alkynes.

Important distinction: Terminal alkynes contain an acidic hydrogen attached to the sp-hybridized carbon. Internal alkynes do not have this terminal hydrogen.

Group C: Physical Chemistry

These chapters emphasize quantitative chemistry. Pay close attention to units, assumptions, formula selection and the meaning of the calculated result.

Chapter 15

Gaseous State

Kinetic theory of gases, kinetic gas equation, average, most probable and root-mean-square velocities, gas laws, Maxwell-Boltzmann distribution, collision diameter, collision frequency, mean free path, real gases, van der Waals equation, compressibility factor, critical phenomena and liquefaction of gases.

urms = √(3RT / M)
Unit check: When using gas equations, use a consistent unit system. Temperature must be expressed in kelvin when required by the equation.
Chapter 16

Liquid and Solid States

Properties of liquids, surface tension, drop-weight and capillary-rise methods, viscosity, fluidity, Ostwald viscometer, applications of measurements, crystalline and amorphous solids, crystal systems, Bravais lattices, cubic crystals, crystallographic laws and Miller indices.

Laboratory connection: Viscosity measurements are affected by temperature. Therefore, temperature should be kept controlled when comparing measurements between samples.
Chapter 17

Chemical and Ionic Equilibria

Law of mass action, effects of temperature, pressure, concentration and inert gases, salt hydrolysis, common-ion effect, buffer solutions, buffer capacity and range, pH calculations, acid-base titration, Ostwald theory, quinonoid theory and indicator selection.

Kc = [products] / [reactants]
Common mistake: Pure solids and pure liquids are not included in the equilibrium expression when writing K for a heterogeneous equilibrium.
Chapter 18

Colligative Properties

Raoult's law, lowering of vapour pressure, elevation of boiling point, depression of freezing point, osmotic pressure, molecular-weight determination, van't Hoff factor and abnormalities caused by association and dissociation.

ΔTb = iKbm
ΔTf = iKfm
π = iCRT
Common calculation mistake: Molality and molarity are not interchangeable. Check whether the formula requires mass of solvent or volume of solution.
Chapter 19

Chemical Kinetics

Rate of reaction, pseudo-order reactions, differential and integrated rate equations for zero- and second-order reactions, half-life, determination of reaction order, Arrhenius equation, activation energy and selected reaction mechanisms.

Zero order: [A] = [A]0 − kt
Second order: 1/[A] = 1/[A]0 + kt

For a first-order reaction, a plot of ln[A] against time gives a straight line with slope −k.

First order: ln[A] = ln[A]0 − kt
Chapter 20

Thermochemistry and Thermodynamics

Thermodynamic terms, Hess's law, bond energy, isothermal expansion, reversible and irreversible expansion, bomb calorimetry, enthalpy, heat of physical changes, heat capacities, relation between Cp and Cv, Kirchhoff's equation, calorific value and numerical problems.

ΔH = Hproducts − Hreactants
Numerical approach: Write the known quantities first, select the appropriate equation, substitute values with units, calculate the result and finally state what the sign and magnitude of the result mean.

Common Chemistry Mistakes to Avoid

CHE-101 Quick Check

1. Which quantum number identifies the subshell?
The azimuthal quantum number, l, identifies the subshell.
2. What is the main difference between SN1 and SN2 kinetics?
SN1 rate depends primarily on the substrate concentration, whereas SN2 rate depends on both the substrate and nucleophile concentrations.
3. Why is temperature written in kelvin in the ideal gas equation?
The gas-law relationship uses absolute temperature, whose zero point corresponds to absolute zero.
4. What does a negative ΔG indicate under constant temperature and pressure?
The process is thermodynamically favourable in the forward direction under the stated conditions.

How to Prepare Chemistry Answers

The amount of detail should match the marks available. A short definition and a detailed mechanism should not be written in the same way.

2 Marks

  • Give the definition directly.
  • Write the important equation if needed.
  • Add one relevant point or example.

5 Marks

  • Start with the principle or definition.
  • Explain the important steps.
  • Include equation, structure or diagram where useful.
  • End with the relevant result or application.

10 Marks

  • Introduce the topic clearly.
  • Explain the principle in sequence.
  • Include mechanisms, equations or diagrams.
  • Discuss important factors or exceptions.
  • Finish with applications or a conclusion.

How to Solve a Chemistry Numerical

For physical chemistry calculations, do not jump directly to the calculator. Use a fixed order so that mistakes are easier to identify.

Step 1: Write the given data

List the numerical values and their units before choosing an equation.

Step 2: Identify what is required

Write the quantity that the question asks you to find. This prevents using a formula for the wrong quantity.

Step 3: Select the equation

Choose the equation that connects the given quantities with the required quantity.

Step 4: Substitute carefully

Convert units before substitution when necessary. Keep enough significant figures during intermediate steps.

Step 5: Interpret the result

State the final answer with its unit and explain what the value means chemically when appropriate.

Final CHE-101 Revision

Before an examination, revise the detailed chapter notes first and then use this shorter list to check whether the major areas have been covered.

About These Notes

These notes are written and edited by Rikrit Nepal, Microbiologist and Founder & Owner of StudyWithMe MSN.

The chapter material is organized to connect definitions with equations, structures, reaction conditions, mechanisms and numerical reasoning. Explanations are kept focused on the actual chemistry so that students can use the material both while learning a chapter and during revision.

Reference framework

If you find a factual error, broken chapter link or unclear explanation, please report it through the Contact page.

How to Use This Page

Start with the chapter you are studying rather than trying to memorize the entire course at once.

For theory topics, understand the reason behind the trend, property or principle. For organic chemistry, learn the reaction together with its conditions and mechanism. For physical chemistry, practise the calculation and check the units before accepting the final answer.

After finishing a chapter, use the Quick Check and the final revision list to see which areas still need another reading.