THE LESSON LIBRARY / CHEMISTRY
Chemistry, explored.
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Foundations of Organic Mechanisms
An organic reaction equation tells us what starts and ends, while a mechanism explains how electrons move between those states. It identifies bond formation, bond cleavage…
Explore lesson ChemistryLessonFourth-Period Ordering and the d Block
Period four has eighteen elements, from potassium to krypton. Its extra width compared with periods two and three comes from a central ten-element d-block region. The familiar…
Explore lesson ChemistryLessonFraction Remaining During Selective Precipitation
Knowing which ion precipitates first is only half the story of a separation. The real test is how *completely* the first ion has been removed by the time the second one starts to…
Explore lesson ChemistryLessonFractional Coefficients and Clearing Them
An odd number of oxygen atoms in the products can make an oxygen molecule on the reactant side seem awkward. A half coefficient is a useful mathematical intermediate: it supplies…
Explore lesson ChemistryLessonFractional Coefficients and Integer Equations
Chemical equations are often displayed with the smallest whole-number coefficients, but a fractional coefficient can describe the same relative chemistry. Multiplying *every*…
Explore lesson ChemistryLessonFractional Distillation
Simple distillation cannot cleanly separate liquids such as ethanol and water, because both evaporate together. Fractional distillation solves this by adding one extra piece of…
Explore lesson ChemistryLessonFractional Distillation and Azeotropes
Simple distillation takes advantage of unequal liquid and vapour compositions. Fractional distillation repeats that vapour–liquid equilibration many times to improve separation.…
Explore lesson ChemistryLessonFractional Distillation of Crude Oil — Carbon Compounds: Introduction
Crude oil contains hydrocarbons with anything from one to more than seventy carbon atoms. To turn it into petrol, jet fuel, diesel and road surfacing, a refinery must sort these…
Explore lesson ChemistryLessonFractional Distillation of Crude Oil — Mixtures and Separation
Crude oil, pumped from deep underground, is a thick, dark liquid that is of little use as it is. Yet it becomes fuel for cars and aircraft, gas for cooking, lubricating oil and…
Explore lesson ChemistryLessonFractional Distillation of Liquid Air
Hospitals need pure oxygen, food factories need pure nitrogen and welders need argon. All three come from the same free and endless raw material: the air. Because air is a…
Explore lesson ChemistryLessonFragmentation of Alcohols, Amines and Halogenoalkanes
Alcohols, amines and halogenoalkanes all contain a heteroatom — oxygen, nitrogen or a halogen — bonded to carbon. When their molecular ions break apart in a mass spectrometer…
Explore lesson ChemistryLessonFragmentation of Carbonyl Compounds
Ketones and aldehydes often give recognisable fragments in electron-ionisation mass spectra. One major route is cleavage at a bond next to the carbonyl carbon. The charged…
Explore lesson ChemistryLessonFragmentation of the Molecular Ion
If a mass spectrum showed only the molecular ion, it would tell you the mass of a molecule but little else. In practice, electron impact spectra contain dozens of peaks at lower…
Explore lesson ChemistryCollectionFree Chemistry Experiments
Explore guided chemistry lessons and experiment stations. Predict, change a variable and explain the result in a simplified learning model.
Explore lesson ChemistryCollectionFree Chemistry Notes & Interactive 3D Labs
Explore 4,500 free chemistry notes across 99 units, interactive 3D labs, worked examples and practice for school, Class 11–12, NEET/JEE and further study.
Explore lesson ChemistryLabFree Chemistry Notes & Interactive 3D Labs
Explore 4,500 free chemistry notes across 99 units, interactive 3D labs, worked examples and practice for school, Class 11–12, NEET/JEE and further study.
Explore lesson ChemistryLessonFree Energy in Living Systems
Cells maintain concentration gradients, build complex molecules and carry out reactions that would not proceed if all components were allowed to equilibrate in one vessel. This…
Explore lesson ChemistryLessonFree Expansion and Path Dependence
A gas expanding into a vacuum meets no mechanical opposition at the boundary, so its pressure-volume work is zero. This differs from a reversible expansion over the same volume…
Explore lesson ChemistryLessonFree-Electron Model of Metals
Metal atoms often contribute electrons that move through an extended crystal rather than remaining on one bond. The free-electron model makes a deliberately severe approximation…
Explore lesson ChemistryLessonFree-Energy Sampling
The lowest-energy structure is not the whole thermodynamic story. A molecular system occupies ensembles of states, and free energy includes the number and accessibility of…
Explore lesson ChemistryLessonFree-Energy Surfaces in Solution
A gas-phase potential-energy surface assigns electronic energy to one nuclear geometry. A solution reaction takes place amid many moving solvent molecules, and a single optimised…
Explore lesson ChemistryLessonFree-Ion Terms: Russell–Saunders Coupling
A diagram labelled t₂g³e_g⁰ is a one-electron occupancy description. Electronic spectra involve transitions between many-electron states, so the combined orbital and spin angular…
Explore lesson ChemistryLabFree-radical chain
A free-radical chain reaction: initiation, propagation and termination.
Explore lesson ChemistryLessonFree-Radical Halogenation of Alkanes
Alkanes lack the π bond that makes alkenes receptive to many addition reactions, but they can react with halogens under suitable light or heat. Free-radical halogenation replaces…
Explore lesson ChemistryLessonFree-Radical Initiation
Free-radical polymerisation begins by generating reactive radicals. Heat, light or redox chemistry can decompose an initiator; however, not every radical produced successfully…
Explore lesson ChemistryLessonFree-Radical Polymerization
Free-radical polymerization is a prominent chain-growth route for vinyl monomers. A radical adds across an alkene, and the new chain end remains radical so it can add again. That…
Explore lesson ChemistryLessonFreezing and Solidifying
Water in an ice-cube tray becomes solid in the freezer, molten metal hardens inside a mould and hot candle wax sets as it drips. Each is an example of freezing, also called…
Explore lesson ChemistryLessonFreezing-Point Depression
When a solute remains mainly in the liquid rather than entering the solvent's crystal, the mixed liquid can stay stable down to a temperature below the pure solvent's freezing…
Explore lesson ChemistryLessonFrenkel Defects
A Frenkel defect occurs when an ion leaves its regular lattice site and takes an interstitial position within the crystal. The result is one vacancy and one interstitial particle…
Explore lesson ChemistryLessonFrequency Scaling and Anharmonicity
A computed Hessian produces frequencies for small vibrations in a quadratic potential near one optimized structure. Experimental infrared or Raman peaks usually involve…
Explore lesson ChemistryLessonFreundlich Adsorption Isotherm
Many real adsorbents have sites that are far from identical. An empirical power law can describe uptake across a useful pressure range without claiming a perfect monolayer. The…
Explore lesson ChemistryLessonFreundlich and Temkin Isotherms
Identical independent sites are the defining simplification of Langmuir adsorption, yet practical carbons, oxides and catalysts contain pores, edges and chemical groups of…
Explore lesson ChemistryLessonFriedel–Crafts Acylation
Friedel–Crafts acylation installs a carbonyl-containing acyl group on an aromatic ring, usually by reacting an acyl chloride with a Lewis acid such as AlCl₃. The product after…
Explore lesson ChemistryLessonFriedel–Crafts Alkylation
Friedel–Crafts alkylation makes a new bond between an aromatic ring and an alkyl group. An alkyl halide activated by a Lewis acid, commonly AlCl₃, supplies a carbon electrophile.…
Explore lesson ChemistryLessonFrom Atomic Mass to Atomic Number
Mendeleev's table worked brilliantly, but it had a puzzle at its heart. In a few places he had to put a heavier element before a lighter one to keep similar elements together.…
Explore lesson ChemistryLessonFrom Atoms to Amounts: A Preview
A single carbon atom has a mass of about 2 × 10⁻²³ g. No balance can weigh one atom, and no one could ever count the atoms in a spoonful of sugar. Yet chemists need to know how…
Explore lesson ChemistryLessonFrom Dalton's Circles to Berzelius's Letters
The neat letters H, O and Fe that fill chemistry books today were not always used. For centuries, people who studied materials drew pictures and secret signs. In the early…
Explore lesson ChemistryLessonFrom Formula to Name: Guided Practice
Going from a name to a formula is one skill; going the other way is another. Faced with FeCl₃, Na₂SO₄ or N₂O, you need to recognise the pieces of the formula and turn them back…
Explore lesson ChemistryLessonFrom Hydrogen to Many-Electron Atoms
Hydrogen gave us exact orbitals, energies and quantum numbers. Every other atom has at least two electrons, and those electrons repel each other. That single extra ingredient…
Explore lesson ChemistryLessonFrom Laboratory Flask to Chemical Plant
A laboratory reaction may be convincing when a small flask gives a pure product once. A chemical plant faces a different question: can it produce the material repeatedly, at a…
Explore lesson ChemistryLessonFrom Mechanism to Catalyst Descriptor
Testing every possible metal, support, ligand and condition is impractical. A descriptor compresses mechanistic knowledge into a variable that may predict performance across…
Explore lesson ChemistryLessonFrom Molecules to Extended Solids
The structure of an isolated water molecule can be described by three atomic positions, molecular orbitals and discrete energy levels. A copper wire, silicon wafer or salt…
Explore lesson ChemistryLessonFrom Molecules to Macroscopic Thermodynamics
Classical thermodynamics is a remarkably powerful framework. From a handful of laws it tells us how internal energy, enthalpy, entropy and Gibbs energy are related, and it…
Explore lesson ChemistryLessonFrom Name to Formula: Guided Practice
Chemical names are not random labels. A systematic name such as "copper(II) nitrate" or "dinitrogen monoxide" contains all the information you need to write the formula, if you…
Explore lesson ChemistryLessonFrom Orbits to Orbitals
Bohr's rings help display hydrogen energy levels, but modern chemistry does not treat an electron as a small planet following one measured circle. An orbital is a quantum state…
Explore lesson ChemistryLessonFrom Pollution Control to Pollution Prevention
Traditional pollution control often begins when a factory has already created a waste stream. Scrubbers, filters and wastewater treatment can protect health and must be used…
Explore lesson ChemistryLessonFrom Rate Laws to Reaction Dynamics
A measured rate law can tell us that doubling a concentration doubles or quadruples a reaction rate. It does not by itself reveal exactly how bonds break and form.…
Explore lesson ChemistryLessonFrom the Molecular Hamiltonian to Predictions
Computational chemistry starts with a physical model before it starts with software. For an isolated collection of electrons and nuclei in a common nonrelativistic approximation…
Explore lesson ChemistryLessonFrom Word Equations to Symbol Equations
A word equation identifies substances; a symbol equation represents them with chemical formulas. Translation is not a letter-by-letter abbreviation. The formula of each reactant…
Explore lesson ChemistryLessonFrontier Molecular Orbital Theory
A complete molecular-orbital calculation can contain many occupied and empty levels, yet a useful first prediction often needs only the orbitals nearest the boundary between…
Explore lesson ChemistryLessonFrontier Molecular Orbitals of Conjugated π Systems
Pericyclic arrows show which bonds change, but they do not explain why one geometry works and another fails. The explanation begins with pi molecular orbitals. A useful first…
Explore lesson ChemistryLessonFrost Diagrams for Transition Metals
A transition metal may have several oxidation states, and a list of potentials can be hard to visualise. A Frost diagram places oxidation state on the horizontal axis and a…
Explore lesson ChemistryLabFroth flotation
Froth flotation: oil-coated sulfide ore rises with air bubbles; sand stays behind.
Explore lesson ChemistryLessonFroth Flotation at an Introductory Level
Froth flotation can concentrate some valuable minerals, especially many sulfide minerals, from crushed ore. It works through differences in particle-surface behavior in water.…
Explore lesson ChemistryLessonFructose and Ketose Chemistry
Fructose and glucose have the same molecular formula but different carbonyl positions. That one connectivity change shifts carbon numbering and the position where a cyclic sugar…
Explore lesson ChemistryLessonFrustrated Lewis Pairs
A Lewis acid and Lewis base normally form an adduct: the base donates an electron pair to the acid. Yet some bulky acid–base combinations remain reactive because close…
Explore lesson ChemistryLessonFuel Cell Thermodynamics and Efficiency
A hydrogen fuel cell combines hydrogen and oxygen to form water while sending electrons through an external circuit. Thermodynamics sets the maximum reversible electrical work…
Explore lesson ChemistryLessonFuel Cells
A fuel cell converts the chemical free energy of supplied fuel and oxidant into electrical output while reactants continue to arrive. It shares anode oxidation, cathode…
Explore lesson ChemistryLessonFuel-Cell Electrochemistry
A battery stores its reactants inside its case; when they are used up, it must be recharged or replaced. A fuel cell is different: fuel and oxidant flow in continuously and…
Explore lesson ChemistryLessonFugacity and Real Gases
Real gas molecules attract and repel one another, so their molar volume is not exactly RT/p. The ideal-gas chemical-potential formula then fails if ordinary pressure is inserted…
Explore lesson ChemistryLessonFunctional Group Interconversion
Many target molecules contain a functional group that is awkward to form directly at the moment a carbon skeleton is assembled. Retrosynthesis can replace it on paper with a…
Explore lesson ChemistryLessonFunctional Group Interconversion in Planning
A target may not display the functional group required by the most attractive carbon–carbon bond-forming reaction. Retrosynthesis can replace one target group with a precursor…
Explore lesson ChemistryLessonFunctional Group Interconversions
Alcohols, phenols, and ethers are connected to other functional groups through predictable transformations. An alkene can hydrate to an alcohol, an alcohol can become a halide or…
Explore lesson ChemistryLessonFunctional Group Isomerism
Molecular formulas alone do not identify organic functional groups. C₂H₆O can mean an alcohol or an ether, compounds with markedly different characteristic reactions.…
Explore lesson ChemistryLabFunctional group tests
Test an unknown organic compound with reagents and work out what it is.
Explore lesson ChemistryLessonFunctional Groups as Reactive Sites — Carbon and its Compounds
Two organic molecules can have similar carbon chains but react differently because one contains an –OH group and the other a C=C bond. The carbon skeleton sets size and shape; a…
Explore lesson ChemistryLessonFunctional Groups as Reactive Sites — Organic Chemistry: Basic Principles
Organic structures become easier to read when recurring atom patterns are recognised. An –OH attached to saturated carbon, a C=O within a chain, a C=O at a chain end and a –COOH…
Explore lesson ChemistryLessonFunctional-Group Identification from Formulae
The same molecular formula can represent an alcohol, ether or another family. A functional-group identification question is therefore a reading task: trace bonds, interpret…
Explore lesson ChemistryLessonFunctional-Group Priority in Naming
A molecule may contain an acid, alcohol, amine and halogen at once. Its name cannot give every group the same suffix role. Systematic nomenclature selects a principal…
Explore lesson ChemistryLessonFundamental Constants and SI Definitions
Constants connect atoms to laboratory quantities: moles to entity counts, kelvin to energy and charge per particle to charge per mole. Some constants have exact numerical values…
Explore lesson ChemistryLessonFusion and Nucleosynthesis
Every atom of carbon in your body, every atom of oxygen you breathe and every atom of gold in a wedding ring was made by nuclear reactions. Hydrogen and helium date from the…
Explore lesson ChemistryLessonGaining and Losing Electrons to Form Ions
Table salt is not made of sodium atoms and chlorine atoms. It is made of ions — sodium particles that have lost an electron and chloride particles that have gained one. Ions are…
Explore lesson ChemistryLabGalvanic cell
Build a galvanic cell from two half-cells and watch it produce a voltage as it discharges.
Explore lesson ChemistryLessonGalvanic Cell Anatomy
A galvanic cell produces electrical work by separating a spontaneous oxidation from its matching reduction. Its physical parts are not arbitrary: electrodes provide…
Explore lesson ChemistryLabGalvanic cell Learning Model
Explore the free galvanic cell chemistry station. Read the model assumptions, make a prediction and compare the numerical and visual results.
Explore lesson ChemistryLessonGalvanic Cell Mixed Calculations
A mixed galvanic-cell problem may ask for electrode roles, cell notation, standard voltage, nonstandard voltage, and Gibbs energy together. The reliable sequence begins with…
Explore lesson ChemistryLessonGalvanic Versus Electrolytic Cells
Galvanic and electrolytic cells both separate oxidation and reduction between electrodes. They differ in energy direction. A galvanic cell lets a spontaneous reaction deliver…
Explore lesson ChemistryLessonGalvanising and Sacrificial Protection
Zinc-coated steel is used outdoors because zinc does more than cover the iron. An intact coating blocks water and oxygen, like other barriers. If a small region is damaged under…
Explore lesson ChemistryLessonGalvanizing Iron
Galvanizing coats iron or steel with zinc. The zinc layer blocks contact with the environment, and zinc can also oxidize preferentially near a small exposed iron area when an…
Explore lesson ChemistryLessonGamma Emission, Isomers and Internal Conversion
Alpha and beta decay change the identity of a nucleus, but they very often leave the daughter in an excited state. The nucleus then sheds its surplus energy without changing Z or…
Explore lesson ChemistryLessonGamma Radiation from Nuclear Excitation
After a nuclear transformation, the daughter can remain in an excited state. It may release some of that extra energy as a gamma photon. Unlike an alpha or beta emission, this…
Explore lesson ChemistryLessonGangue and Ore Grade
An ore is rarely a pure mineral. It contains valuable material mixed with gangue, the material not being sought in that extraction process. Grade describes how much of the feed…
Explore lesson ChemistryLessonGas Adsorption Factors
Gas adsorption experiments reveal how a solid's surface responds to its environment. Increasing gas pressure often increases uptake; raising temperature often reduces equilibrium…
Explore lesson ChemistryLessonGas Amount and Molar Volume
Gas volume can provide a convenient route to moles, but volume alone does not determine amount. A gas expands when warmed and contracts when compressed. Every quoted molar volume…
Explore lesson ChemistryLessonGas Amounts from Pressure, Volume and Temperature
A gas-volume measurement may come with its own pressure and temperature rather than a supplied molar volume. The ideal-gas relation PV = nRT converts that measurement to a mole…
Explore lesson ChemistryLessonGas and Solution Terms
Gas and solution language describes how particles share space and how chemical potential depends on composition. Pressure is not the same as an amount of gas, and a gas…
Explore lesson ChemistryLessonGas Chromatography
Gas chromatography, or GC, separates compounds that can be vaporised and pass through a heated column without unacceptable decomposition. A carrier gas moves them; interactions…
Explore lesson ChemistryLessonGas Collected over Water
Collecting a reaction gas over water is convenient, but the gas space above the water contains both the desired product and water vapour. A pressure measurement usually reports…
Explore lesson ChemistryLessonGas Collection and Reaction Amount
A gas-producing reaction can reveal how much substance reacted even when a solid product is hard to isolate. First convert the measured gas volume to moles using the conditions…
Explore lesson ChemistryLessonGas Density and Molar Mass — Physical Chemistry Problem Solving
Gas density is not a fixed fingerprint unless pressure and temperature are specified. A gas becomes denser when compressed and usually less dense when heated at constant…
Explore lesson ChemistryLessonGas Density and Molar Mass — States of Matter: Gases and Liquids
Gas density is not a single fixed number for a substance. The same gas can be compressed or warmed, changing mass per unit volume. The ideal-gas equation connects density with…
Explore lesson ChemistryLabGas diffusion Learning Model
Explore the free gas diffusion chemistry station. Read the model assumptions, make a prediction and compare the numerical and visual results.
Explore lesson ChemistryLessonGas Equilibrium from Partial Pressures
Gas-equilibrium calculations often provide total pressure and mole amounts rather than each species' partial pressure. The bridge is the mole fraction. Because reactions can…
Explore lesson ChemistryLessonGas Equilibrium with Changing Mole Number
For gas-phase equilibria, the natural variable is partial pressure rather than concentration. If the number of gas molecules changes during reaction, the total amount of gas…
Explore lesson ChemistryLabGas laws and kinetic theory
Real molecular dynamics: gas particles bounce in a box and the pressure is measured from wall hits.
Explore lesson ChemistryLessonGas Mixtures and Dalton's Law
A gas vessel can contain several species at once. A pressure gauge measures their combined pressure, while a reaction or measurement may depend on the contribution of just one…
Explore lesson ChemistryLessonGas Pressure and Particle Collisions
A balloon stays inflated, a football feels firm and a bicycle tyre can support a rider's weight — all because of gas pressure. But gas is invisible and mostly empty space, so…
Explore lesson ChemistryLessonGas Production and Effervescence
Drop an antacid tablet into water and it fizzes wildly. Heat a pan of water and it also bubbles. Open a bottle of sparkling water and bubbles stream up the sides. All three…
Explore lesson ChemistryLessonGas Solubility and Pressure
Sealed sparkling water holds more dissolved carbon dioxide than the same drink after it has been open for a while. The pressure of CO₂ above the liquid changes when the container…
Explore lesson ChemistryLessonGas Solubility and Temperature — Solutions and Colligative Properties
Gas solubility is controlled by more than a single pressure rule. At a fixed temperature, raising the gas's partial pressure generally raises its equilibrium dissolved amount in…
Explore lesson ChemistryLessonGas Solubility and Temperature — Solutions and Concentration
Cold water commonly holds more of many dissolved gases than warm water at the same gas partial pressure. Warming a liquid can therefore release bubbles without a chemical…
Explore lesson ChemistryLessonGas Tests in Qualitative Analysis
Gas evolution is evidence only when the gas itself is identified. Hydrogen, oxygen, carbon dioxide, ammonia, chlorine and sulfur dioxide have different chemical responses. The…
Explore lesson ChemistryLessonGas Variables and Measured State
A gas has no fixed shape or volume of its own, so a statement such as “the balloon expanded” is incomplete without the conditions. Four quantities provide a compact description…
Explore lesson ChemistryLessonGas Volume Ratios at Matching Conditions
Gases offer a shortcut in some stoichiometry problems: at the same temperature and pressure, their volumes are proportional to their mole amounts. A balanced equation can then…
Explore lesson ChemistryLessonGas Volumes at Different Conditions
A reaction may produce a gas measured at one temperature and pressure, while a question asks for its volume under another set of conditions. There is no universal volume occupied…
Explore lesson ChemistryLessonGas Volumes in Chemical Reactions
A balanced equation gives ratios of reacting particles and moles. When every compared substance is gaseous at the same pressure and temperature, Avogadro's law lets those mole…
Explore lesson ChemistryLessonGas-Law Data Interpretation
Gas-law data can look convincing even when a graph uses the wrong axes or a calculation mixes Celsius with kelvin. Interpreting a table requires more than fitting a line.…
Explore lesson ChemistryLessonGas-Law Formulae
Gas formulae link measurable pressure, volume and temperature to amount of substance. The ideal-gas equation is versatile because it also describes each component of an ideal…
Explore lesson ChemistryLessonGas-Mixture Problem-Solving Review
A realistic numerical problem may provide a solid reactant mass, an inert gas already in a vessel, water vapour, and a measured temperature and volume. Solving everything in one…
Explore lesson ChemistryLessonGas-Phase Acidity and Proton Affinity
In water, an acid's products are stabilised by extensive solvent interactions. Remove the solvent, and the energetic problem changes profoundly: an acid must produce an isolated…
Explore lesson ChemistryLessonGas-Phase Kinetics
Gas reactions are often monitored with pressure rather than solution concentration. For an ideal gas mixture, each species' molar concentration is cᵢ=pᵢ/(RT), where pᵢ is partial…
Explore lesson ChemistryLessonGases Have Mass and Volume
Gases are the easiest state of matter to forget about because most of them are invisible. Yet the air around us presses on every surface, fills every container and can be…
Explore lesson ChemistryLessonGaussian Trial Functions for Hydrogen
When the variation principle is applied to hydrogen with the trial function e^(−ζr), the optimum exponent turns out to reproduce the exact 1s orbital, so the calculation gives…
Explore lesson ChemistryLessonGels, Foams and Aerosols
Colloids are not limited to particles in a liquid. A gel can hold much liquid while keeping a solid-like shape; a foam is mostly gas yet can persist as a mound; and an aerosol…
Explore lesson ChemistryLessonGeneral Formulae and Their Conditions
General formulae are powerful when their assumptions are explicit. CₙH₂ₙ₊₂ describes a saturated acyclic hydrocarbon, CₙH₂ₙ describes a simple acyclic monoalkene or a saturated…
Explore lesson ChemistryLessonGeneral Patterns: A + B → AB and Its Relatives
Letter templates reduce a long equation to its structural pattern. A + B → AB suggests joining; AB → A + B suggests splitting; A + BC → AC + B suggests replacement; and AB + CD →…
Explore lesson ChemistryLessonGenetic Information Flow
DNA sequence can be copied, transcribed into RNA and interpreted to make a protein. These are three different processes, each using a template but different chemistry and…
Explore lesson ChemistryLessonGeometric Isomerism and Restricted Rotation
Butane can twist freely about its central C–C bond, and every twisted form interconverts millions of times a second. But-2-ene, with a C=C double bond in the same position…
Explore lesson ChemistryLessonGeometric Isomerism of Alkenes
Restricted C=C rotation can preserve two different arrangements of substituents. These are geometric stereoisomers: their atoms have the same connectivity but different spatial…
Explore lesson ChemistryLessonGeometrical Isomerism in Alkenes
But-2-ene can be drawn with both CH₃ groups on the same side of C=C or on opposite sides. These drawings have the same formula and connectivity, yet they are different…
Explore lesson ChemistryLessonGeometrical Isomerism in Octahedral Complexes
An octahedral complex has six donor positions. Repeated ligands can occupy these positions in more than one non-equivalent way. MA₄B₂ may be cis or trans; MA₃B₃ may be facial or…
Explore lesson ChemistryLessonGeometrical Isomerism in Rings
Restricted rotation is not limited to double bonds. A ring connects atoms in a closed loop, preventing one substituent from being moved freely to the other face without changing…
Explore lesson ChemistryLessonGeometrical Isomerism in Square-Planar Complexes
Four-coordinate complexes can be square planar or tetrahedral. The difference matters for isomerism. A square-planar MA₂B₂ complex can arrange the two A ligands side by side or…
Explore lesson ChemistryLessonGeometry and Coordination Environment
An electron count does not describe where ligands sit. Geometry controls which groups can meet for reductive elimination, which site can bind an alkene and whether an incoming…
Explore lesson ChemistryLessonGeometry Optimization
A molecular geometry calculation searches for nuclear coordinates favored by a chosen electronic-energy model. The model gives an energy surface over bond lengths, angles and…
Explore lesson ChemistryLessonGermanium, Tin and Lead
Carbon and silicon are strongly associated with +4 compounds, but tin and lead commonly form +2 compounds as well. Lead(II) is often more stable than lead(IV) under familiar…
Explore lesson ChemistryLessonGiant Covalent Networks
The word “covalent” does not mean “made of small molecules.” Diamond, graphite and silica contain extended networks of bonded atoms. Their distinct structures explain why some…
Explore lesson ChemistryLessonGiant Covalent Structures: Diamond
Diamond contains only carbon, yet it behaves very differently from small carbon-containing molecules. Its bonds extend through a three-dimensional network rather than stopping at…
Explore lesson ChemistryLessonGiant Covalent Structures: Graphite
Graphite and diamond contain the same element but arrange their bonds differently. Graphite's carbon atoms form extended sheets rather than a four-connected three-dimensional…
Explore lesson ChemistryLessonGiant Covalent Structures: Silicon Dioxide
Silicon dioxide has a formula that resembles carbon dioxide's, but ordinary solid silica is not a collection of O=Si=O molecules. In quartz, silicon and oxygen form an extended…
Explore lesson ChemistryLessonGibbs Energy and Cell Potential — Electrochemistry
Cell voltage measures electrical energy per unit charge. Gibbs-energy change measures energy for a specified amount of reaction. Their connection, ΔG = −nFE, includes the number…
Explore lesson ChemistryLessonGibbs Energy and Cell Potential — Physical Chemistry Problem Solving
A cell potential tells you how much energy each coulomb of charge carries, while a Gibbs-energy change tells you how much useful energy a reaction releases per mole of reaction.…
Explore lesson ChemistryLessonGibbs Energy and Equilibrium Constant
The equation Δ_rG° = −RT ln K connects thermodynamics to equilibrium composition. A negative standard Gibbs energy corresponds to K > 1 for the reaction as written; a positive…
Explore lesson ChemistryLessonGibbs Energy and Spontaneity
Tracking entropy changes of both system and surroundings can be cumbersome. At constant temperature and pressure under suitable conditions, Gibbs energy packages the same…
Explore lesson ChemistryLessonGibbs Energy Away from Standard Conditions
A standard Gibbs-energy value describes a reference composition, while a real reaction mixture may contain different amounts of reactants and products. The current composition…
Explore lesson ChemistryLessonGlass pH Electrodes
A pH meter displays a familiar number, yet its probe actually measures a voltage across an ion-responsive glass membrane and a reference system. The reading becomes pH only after…
Explore lesson ChemistryCollectionGlossary (multilingual)
Study Glossary (multilingual) with 25 free lessons, worked examples, and answered practice questions.
Explore lesson ChemistryLessonGluconeogenesis
When dietary glucose is unavailable, some tissues still require a supply of blood glucose. The liver, and during prolonged fasting the kidney, can produce glucose from lactate…
Explore lesson ChemistryLessonGlucose Structure and Stereochemistry
Glucose is often called simply “a six-carbon sugar,” but its biological identity depends on the exact arrangement of hydroxyl groups along its chain. The open-chain Fischer…
Explore lesson ChemistryLessonGlycogen Synthesis and Breakdown
Glycogen is a branched glucose polymer that lets animals store and mobilise glucose quickly. Liver glycogen supports blood glucose between meals, whereas muscle glycogen mainly…
Explore lesson ChemistryLessonGlycolysis: The Investment Phase
Glycolysis does not immediately make ATP from incoming glucose. Its first phase spends two ATP equivalents to phosphorylate and rearrange a six-carbon sugar, then splits it into…
Explore lesson ChemistryLessonGlycolysis: The Payoff Phase
The investment phase feeds two molecules of glyceraldehyde 3-phosphate (GAP) into the same payoff sequence. Each GAP is oxidised and transformed into pyruvate while making one…
Explore lesson ChemistryLessonGraham's Law of Effusion
At the same temperature and pressure, lighter ideal-gas molecules generally cross a tiny opening faster than heavier ones. Graham's law quantifies that comparison through the…
Explore lesson ChemistryLessonGraphene Oxide and Reduced Graphene Oxide
Graphene oxide, or GO, is useful because oxygen-bearing groups make carbon sheets easier to disperse and chemically process. Those groups also disrupt the extended electronic…
Explore lesson ChemistryLessonGraphene: Structure and Electronic Properties
Graphene is a single atomic layer of carbon arranged in a honeycomb pattern. Each atom bonds to three neighbors, leaving an out-of-plane p orbital that joins a delocalized…
Explore lesson ChemistryLessonGraphite and Hard-Carbon Anodes
Carbon negative electrodes demonstrate that chemical identity alone does not define an ion-storage mechanism. Crystalline graphite stores lithium in ordered interlayer…
Explore lesson ChemistryLessonGraphite and Silicon Anodes
Graphite and silicon both operate as negative-electrode materials in lithium-ion cells, but they store lithium differently. Graphite accepts lithium between its carbon layers…
Explore lesson ChemistryLessonGravimetric Factors and Calculations
Gravimetric arithmetic begins with the solid actually weighed, not necessarily with the compound first precipitated. Its formula tells how many analyte units each mole contains.…
Explore lesson ChemistryLessonGravity and Magnetic Concentration
After ore is crushed enough to expose distinct grains, some minerals can be separated by physical differences. Gravity methods exploit density-related settling; magnetic methods…
Explore lesson ChemistryLessonGreen Chemistry and Atom Economy in Synthesis Design
A synthesis can reach its target and still consume much more material than appears in the product. Side products, protecting-group steps, solvent and failed conversions create…
Explore lesson ChemistryCollectionGreen Chemistry and Sustainable Design
Study Green Chemistry and Sustainable Design with 40 free lessons, worked examples, and answered practice questions.
Explore lesson ChemistryLessonGreen Chemistry and Sustainable Design: Unit Review
Green chemistry asks designers to prevent hazards and waste at their source. Sustainable design then checks whether a change helps across the full product system. A high-yield…
Explore lesson ChemistryLessonGreen Chemistry and the Future of Industrial Processes
Industrial chemistry must supply materials society uses while reducing waste, greenhouse-gas emissions and hazards. Better catalysts, renewable feedstocks and electrified heat…
Explore lesson ChemistryLessonGreen Chemistry in Synthesis
A synthesis can deliver the correct product yet consume large amounts of reagents and solvent or generate difficult byproducts. Green chemistry asks how to design the…
Explore lesson ChemistryLessonGreen Metrics in Practice: Comparing Two Routes
A practical green-chemistry decision rarely follows one metric. A route with excellent atom economy can be hard to run and purify; a lower-atom-economy route may isolate more…
Explore lesson ChemistryLessonGreen Polymers and Bioplastics
“Bioplastic” is not a single chemical structure or disposal instruction. It may mean a polymer made from biomass, a polymer that biodegrades under certain conditions, or both.…
Explore lesson ChemistryLessonGreenhouse Gases and Radiative Forcing
Nitrogen and oxygen make up 99% of dry air, yet they are almost transparent to the infrared radiation Earth emits. The warming of the planet is controlled instead by trace gases…
Explore lesson ChemistryLessonGrignard Addition to Carbonyls
Hydride reduction adds H to a carbonyl carbon; a Grignard reagent adds a carbon group instead. In RMgX, the carbon–magnesium bond is polarised so the R carbon behaves…
Explore lesson ChemistryLessonGroup 0: The Noble Gases
The final column of the periodic table holds a family that for a long time seemed to have no chemistry at all: helium, neon, argon, krypton, xenon and radon. These noble gases…
Explore lesson ChemistryLessonGroup 1 Descriptive Chemistry
Lithium, sodium, potassium, rubidium and caesium are soft, reactive metals that commonly form +1 compounds. Their shared outer ns¹ configuration explains much of their behaviour…
Explore lesson ChemistryLessonGroup 1: The Alkali Metals
The first column of the periodic table holds some of the most striking elements in chemistry: metals so soft you can cut them with a knife, light enough to float on water, and so…
Explore lesson ChemistryLessonGroup 2 Descriptive Chemistry
Group 2 elements share an outer ns² configuration and commonly form +2 compounds, yet their salts are not uniformly soluble. Hydroxides become generally more soluble down the…
Explore lesson ChemistryLessonGroup 2 Metals with Water and Oxygen
Group 2 metals commonly form +2 compounds, yet beryllium, magnesium, calcium, strontium and barium do not react with cold water in identical ways. Oxygen reactions also depend on…
Explore lesson ChemistryLessonGroup 2: The Alkaline Earth Metals
Next door to the alkali metals sits Group 2: beryllium, magnesium, calcium, strontium, barium and radium. These alkaline earth metals are still reactive, but noticeably calmer…
Explore lesson ChemistryLessonGroup 7: The Halogens
On the right-hand side of the periodic table, one column before the noble gases, lies a family of highly reactive non-metals: fluorine, chlorine, bromine, iodine and astatine.…
Explore lesson ChemistryLessonGroup Eighteen Patterns
Helium, neon, argon, krypton, xenon and radon are group-18 noble gases. Their filled outer-shell configurations help explain why they occur as monoatomic gases and are relatively…
Explore lesson ChemistryLessonGroup Fifteen Overview
Group 15 contains nitrogen, phosphorus, arsenic, antimony and bismuth. Each has an ns²np³ outer configuration: five valence electrons. The shared pattern supports three bonds and…
Explore lesson ChemistryLessonGroup Fourteen Overview
The carbon family runs from carbon and silicon through germanium, tin and lead. Its ns²np² outer pattern gives four valence electrons, but members do not all make the same…
Explore lesson ChemistryLessonGroup I Cations: Insoluble Chlorides
The first classical cation fraction contains ions whose chlorides are sparingly soluble under the scheme's conditions: Ag⁺, Pb²⁺ and Hg₂²⁺. All can yield pale or white chloride…
Explore lesson ChemistryLessonGroup II Cations: Sulfides in Acid
After insoluble chlorides are considered, a classical scheme can isolate metal sulfides that precipitate even in acidic conditions. Acid keeps free S²⁻ extremely low by favouring…
Explore lesson ChemistryLessonGroup III Cations: Hydroxides in Buffered Ammonia
In the chosen classical scheme, iron(III), aluminium and chromium(III) can be separated as hydroxides under a controlled ammonia/ammonium medium. The purpose of the buffer is to…
Explore lesson ChemistryLessonGroup IV Cations: Sulfides in Alkaline Medium
Some metal ions remain dissolved during the acidic sulfide stage but precipitate when the solution becomes less acidic and free S²⁻ increases. In one classical scheme, Zn²⁺…
Explore lesson ChemistryLessonGroup Number and Valence Electrons
The periodic table is not just a list — it is a map of electron arrangements. If you know which column an element sits in, you already know how many electrons are in its outer…
Explore lesson ChemistryLessonGroup One and Group Two Patterns
Groups 1 and 2 make the s-block pattern especially clear. Their common outer configurations, ns¹ and ns², support familiar +1 and +2 ions. Down either group, atoms generally grow…
Explore lesson ChemistryLessonGroup Seventeen Overview
Fluorine, chlorine, bromine, iodine and astatine occupy group 17. Their atoms share an ns²np⁵ outer configuration with seven valence electrons. They commonly form −1 halide ions…
Explore lesson ChemistryLessonGroup Sixteen Overview
Group 16 includes oxygen, sulfur, selenium, tellurium and polonium. The shared ns²np⁴ outer pattern gives six valence electrons, but the elements range from reactive nonmetal…
Explore lesson ChemistryLessonGroup Thirteen Overview
Group 13 begins with boron and continues through aluminium, gallium, indium and thallium. Its common outer-electron pattern is ns²np¹. The apparently simple pattern hides a…
Explore lesson ChemistryLessonGroup Transfer Reactions: The Ene Reaction
An ene reaction joins an alkene bearing an allylic hydrogen to another unsaturated partner. One new bond forms between the partners, the allylic hydrogen transfers, and the ene…
Explore lesson ChemistryLessonGroup V Cations: Insoluble Carbonates
After several less-soluble chloride, sulfide and hydroxide groups have been removed, a classical scheme can separate calcium, strontium and barium as carbonate solids. These…
Explore lesson ChemistryLessonGroup VI Cations: The Soluble Remainder
The final filtrate of a classical cation scheme may still contain Mg²⁺, Na⁺, K⁺ and NH₄⁺. They are not grouped because they share one distinctive precipitate; they are the ions…
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