THE LESSON LIBRARY / CHEMISTRY
Chemistry, explored.
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Brittleness, Strength and Elasticity
Stretch a rubber band and it springs back. Bend a paper clip too far and it stays bent. Drop a glass and it shatters. These three behaviours show how materials respond to forces.…
Explore lesson ChemistryLessonBromination and Nitration of Phenol
Phenol's hydroxyl group donates electron density to its aromatic ring and makes bromination or nitration possible under conditions milder than those required for benzene in many…
Explore lesson ChemistryLessonBrønsted–Lowry Acids in Inorganic Systems
An acid does not need to produce H₃O⁺ in water to count as a Brønsted–Lowry acid. The definition is based on proton transfer: one species donates H⁺ and another accepts it. That…
Explore lesson ChemistryLessonBrownian Motion: Evidence for Moving Particles
In 1827 the botanist Robert Brown looked through a microscope at tiny grains released from pollen floating in water. To his surprise, they never kept still: they jiggled and…
Explore lesson ChemistryLessonBuchwald–Hartwig Amination
Aryl amines occur in a large proportion of drugs, dyes and organic electronic materials. Classical methods for making them, such as nucleophilic aromatic substitution, only work…
Explore lesson ChemistryLessonBuffer Action Revisited
Earlier work introduced buffers as solutions that keep pH nearly constant. At this level we look more closely at the mechanism. A buffer does not stop added acid or base from…
Explore lesson ChemistryLessonBuffer Capacity
Two buffers can have exactly the same pH and yet behave very differently. One may hold its pH after a large dose of acid, while the other collapses after a few drops. The…
Explore lesson ChemistryLessonBuffer Capacity and Limits
Two buffers can have the same initial pH but very different resilience. Their conjugate-pair ratios may match while their total moles differ greatly. Buffer capacity describes…
Explore lesson ChemistryLessonBuffer Capacity Near pKa
A weak-acid buffer contains HA, which can consume added base, and A⁻, which can consume added acid. Near pH = pKa, the two components have similar amounts and the buffer can…
Explore lesson ChemistryLessonBuffer Composition and Action
A buffer moderates, rather than prevents, a pH change. Its two reactive components are usually a weak acid and its conjugate base, or a weak base and its conjugate acid. To…
Explore lesson ChemistryLessonBuffer Design Integrated Problems
A buffer-design problem has at least two independent choices. The HA/A⁻ ratio sets approximate pH; the total amount sets how much acid or base can be absorbed. A complete design…
Explore lesson ChemistryLessonBuffer Failure and Extremes
A buffer resists pH change only while it has enough of the component needed to consume the added acid or base. An HA/A⁻ mixture can handle acid through A⁻ and base through HA.…
Explore lesson ChemistryLessonBuffer Preparation
Preparing a buffer involves two choices: a conjugate pair whose pKa is near the desired pH, and enough total material to absorb expected disturbances. The acid-to-base ratio…
Explore lesson ChemistryLessonBuffer Ratio and Henderson–Hasselbalch
A buffer contains a weak acid and its conjugate base in comparable amounts. Its pH depends on the ratio of the two, which makes buffer calculations quick once the ratio is known.…
Explore lesson ChemistryLessonBuffer Ratio Design
Once a conjugate pair has been chosen, the next decision is how much of each form to use. Two separate numbers must be fixed: the ratio of base to acid, which sets the pH, and…
Explore lesson ChemistryLessonBuffers and Biological pH
Human blood is held between pH 7.35 and 7.45. Outside roughly 6.8 to 7.8, enzymes and membranes cannot function and life is not sustained. Remarkably, the main buffer in blood…
Explore lesson ChemistryLessonBuffers in Everyday Life
Add one drop of hydrochloric acid to a beaker of pure water and the pH can fall from 7 to about 4. Add the same drop to your blood and its pH barely moves from 7.4. Blood is a…
Explore lesson ChemistryLessonBuilding a Chemistry Revision Plan
Finishing a course does not mean every idea is equally available when a problem appears. A student may remember a formula but apply it to the wrong quantity, or solve an…
Explore lesson ChemistryLessonBuilding a Reactivity Series from Evidence
A reactivity series can be built from observations instead of memorised first. If metal A displaces metal B from a salt solution, A is generally placed above B for that reaction…
Explore lesson ChemistryLessonBuilding an Electrolytic Cell
An electrolytic cell needs more than two pieces of metal in a beaker. It needs a suitable power source, conducting electrodes, an ion-conducting liquid or melt, and a complete…
Explore lesson ChemistryLessonBuilding Models of Carbon Molecules
Formulae on paper are flat, but molecules are three-dimensional. To really understand the tetrahedral carbon atom, zig-zag chains and flat double-bonded molecules, chemists build…
Explore lesson ChemistryLessonBurning Elements in Oxygen
When an element burns in oxygen it forms an oxide. Some elements burn with spectacular colours: magnesium with a blinding white light, sulfur with a delicate blue flame, sodium…
Explore lesson ChemistryLessonButadiene Pi Molecular Orbitals
Butadiene contains four connected p orbitals and four pi electrons. It is the simplest open-chain system large enough to show two occupied pi MOs, two unoccupied pi MOs and a…
Explore lesson ChemistryLessonButane Conformations
Butane reveals why not all staggered conformations have the same energy. Looking along its central C₂–C₃ bond, each viewed carbon carries one methyl and two hydrogen groups. The…
Explore lesson ChemistryLessonButler–Volmer Equation
Electrode kinetics shows that anodic and cathodic rate constants depend exponentially on potential. The Butler–Volmer equation combines these two exponentials into a single…
Explore lesson ChemistryLessonButler–Volmer with Concentration Terms
The simple Butler–Volmer equation treats concentrations at the reaction plane as fixed. This is a good starting point for small currents or vigorous transport, but a reacting…
Explore lesson ChemistryLessonC–C Disconnections via Organometallic Reagents
Carbon–carbon bonds can be planned by assigning one fragment nucleophilic carbon character and the other electrophilic character. Organometallic reagents make this especially…
Explore lesson ChemistryLessonC–H Activation
Carbon–hydrogen bonds are everywhere in organic molecules, yet they are strong, non-polar and almost identical to one another. Traditionally chemists introduced reactivity by…
Explore lesson ChemistryLessonC–H Stretches and Hybridisation
Almost every organic molecule contains C–H bonds, so you might expect their IR bands to be useless for identification. In fact, the precise position of the C–H stretch reveals…
Explore lesson ChemistryLessonCalcination of Carbonate Ores
Some carbonate minerals are heated so they decompose into an oxide and carbon dioxide. This treatment is called calcination in the introductory extraction pathway. The oxide may…
Explore lesson ChemistryLessonCalcium as a Biological Signal
Every heartbeat, every muscle twitch and every release of a neurotransmitter is triggered by a brief rise in the calcium ion concentration inside a cell. Calcium is not a…
Explore lesson ChemistryLessonCalcium Carbonate and Lime Chemistry
Calcium carbonate, calcium oxide and calcium hydroxide form a compact reaction network with major material uses. Limestone contains CaCO₃. Heating it under appropriate conditions…
Explore lesson ChemistryLessonCalculating a Salt's Lattice Enthalpy
The Born–Haber cycle becomes a quantitative tool when all but one enthalpy are known. For NaCl, the direct standard formation enthalpy equals sodium atomization, sodium…
Explore lesson ChemistryLessonCalculating Atom Economy
Atom-economy arithmetic is simple once the equation is balanced, but most errors happen before division: omitting a reagent, forgetting a coefficient or counting the wrong…
Explore lesson ChemistryLessonCalculating Density
Knowing what density means is only half the job; chemists also need to measure it. Density is never read directly from a single instrument — it is calculated from two…
Explore lesson ChemistryLessonCalculating Gas Products in Extraction
Extraction reactions can produce CO₂ or SO₂. A balanced stage equation gives a theoretical amount when feed and conversion are known, but the quantity leaving a plant may differ…
Explore lesson ChemistryLessonCalculating Metal from Ore Mass
An ore mass does not directly state a metal mass. A calculation may need three separate filters: what fraction of ore is valuable mineral, what fraction of that mineral is the…
Explore lesson ChemistryLessonCalculating Molarity from Mass
A balance gives grams, while molarity requires moles. The bridge is molar mass. After converting a weighed solute mass to formula amount, divide by the final solution volume.…
Explore lesson ChemistryLessonCalculating pH from Hydronium Concentration
The pH equation is short, but using it well requires more than typing a number into a calculator. Hydronium concentration must be positive, units must be interpreted…
Explore lesson ChemistryLessonCalculating Photon Wavelength
An energy-level diagram becomes a prediction when its gap is turned into a wavelength. For a photon, E = hc/λ, so λ = hc/E. This page practises that calculation with units…
Explore lesson ChemistryLessonCalculating Protons, Neutrons and Electrons
Most introductory atomic-structure numericals use only three counting rules. The challenge is deciding which information supplies each rule and keeping the signs consistent. A…
Explore lesson ChemistryLessonCalculating Reductant Demand
Planning oxide reduction requires enough reductant to remove oxygen under a chosen reaction model. Convert oxide feed to moles, use its balanced ratio with carbon, CO or another…
Explore lesson ChemistryLessonCalculating Relative Atomic Mass from Isotopes
Relative atomic mass is calculated by combining isotope masses with how common those isotopes are. The arithmetic is straightforward when the data are organised correctly. Most…
Explore lesson ChemistryLessonCalculating Relative Molecular Mass
Knowing the definition of relative molecular mass is one thing; calculating it quickly and reliably is another. This page works carefully through three of the most important…
Explore lesson ChemistryLessonCalculating Rf Values
Comparing spot heights works well when every sample is on the same piece of paper. But what if a laboratory in another city wants to compare its result with yours, and its…
Explore lesson ChemistryLessonCalculating Spin-Only Moments
The spin-only formula becomes most useful when its common values are familiar. For one through five unpaired electrons, the predicted moments are about 1.73, 2.83, 3.87, 4.90 and…
Explore lesson ChemistryLessonCalculating Tetrahedral CFSE
Tetrahedral CFSE uses the same bookkeeping idea as octahedral CFSE but a different diagram. The two e orbitals lie lower at −0.6Δ_t each, while three t₂ orbitals lie higher at…
Explore lesson ChemistryLessonCalculating Yield from Starting Masses
A full yield problem often begins with two reactant masses and ends with a measured product mass. It has three decisions: how many moles of each reactant are available, which one…
Explore lesson ChemistryLessonCalibration Curves
An analytical instrument usually measures a signal, not concentration directly. Absorbance, peak area or ion current must be related to known amounts of analyte. A calibration…
Explore lesson ChemistryLessonCalibration Curves and Linear Regression
Many analytical instruments produce a signal, not concentration directly. Calibration standards establish a relation between known analyte levels and measured response. A common…
Explore lesson ChemistryLessonCalibration Curves in Colorimetry
Calculating a concentration from A = εcl requires an accurate value of ε for exactly the instrument, wavelength and conditions in use. Often that value is not known, or a simple…
Explore lesson ChemistryLabCalorimetry
A virtual calorimeter: measure a temperature change and work out ΔH.
Explore lesson ChemistryLessonCalorimetry and Heat Balance
Calorimetry measures temperature changes and uses heat capacities to infer energy transfers. In a well-insulated assembly, heat lost by a hot part or reaction is gained by the…
Explore lesson ChemistryLessonCalorimetry Energy Balance
A reaction in a calorimeter changes the temperature of its surroundings. To infer reaction heat, account for every part that warms or cools: usually the solution and sometimes…
Explore lesson ChemistryLessonCanal Rays and Positive Particles
Negative electron beams were not the only charged streams studied in discharge tubes. Positive-ion beams also appeared under appropriate conditions. These canal rays helped show…
Explore lesson ChemistryLessonCandle Flames: Physical and Chemical Changes Together
A burning candle looks simple, but it is a small chemistry laboratory. In a single flame you can see a solid melting, a liquid climbing a wick, a liquid turning to gas and a gas…
Explore lesson ChemistryLessonCannizzaro Reaction
What happens when an aldehyde has no alpha hydrogen and is placed in concentrated base? It cannot form the usual enolate that begins an aldol reaction. Some such aldehydes…
Explore lesson ChemistryLessonCannizzaro Reaction Concept
Some aldehydes without alpha hydrogens react under strongly basic conditions by a pathway different from aldol condensation. In the Cannizzaro reaction, one aldehyde molecule is…
Explore lesson ChemistryLessonCarbanion Stability
Carbocations are electron-poor and are stabilised by anything that donates electron density. Carbanions are the mirror image: a carbon carrying a full negative charge and a lone…
Explore lesson ChemistryLessonCarbanions and Their Stability
A carbanion carries negative formal charge at carbon in a useful Lewis picture, often with a lone pair. Such species can act as bases or nucleophiles, but their stability varies…
Explore lesson ChemistryLessonCarbenes and Nitrenes Introduction
Most carbon atoms in stable molecules have four bonds. A carbene has only two, together with two non-bonding electrons, so it has just six valence electrons and is neutral.…
Explore lesson ChemistryLessonCarbocation Rearrangements
Carbocations can change their carbon skeleton or charge position before a nucleophile traps them. A neighbouring C–H or C–C bond can migrate with its electron pair to the…
Explore lesson ChemistryLessonCarbocation Stability
Carbocations appear in mechanisms for SN1, E1, and some electrophilic additions. Their relative stability helps predict which intermediates and rearrangements are plausible.…
Explore lesson ChemistryLessonCarbocation Stability and Fragmentation
A molecular ion can usually break in several places, yet the resulting spectrum is not a random jumble of equally sized peaks. A few fragments tower over the rest. The reason…
Explore lesson ChemistryLessonCarbocations and Their Stability
A carbocation is an electron-deficient positively charged carbon species. It can appear as a proposed intermediate in some organic mechanisms, but not every reaction that breaks…
Explore lesson ChemistryLabCarbohydrate structures
Glucose closes into a ring (α or β), and sugars join by glycosidic links.
Explore lesson ChemistryLessonCarbon and Hydrogen in the Reactivity Series
Carbon and hydrogen are non-metals, yet they appear in many school metal reactivity lists. They are inserted for comparison, not because they have become metals. Carbon helps…
Explore lesson ChemistryCollectionCarbon and its Compounds
Study Carbon and its Compounds with 80 free lessons, worked examples, and answered practice questions.
Explore lesson ChemistryLessonCarbon and its Compounds Unit Review
Carbon's four-bond capacity and ability to connect to itself create chains, branches and rings. Multiple bonds and functional groups add further diversity. This review links…
Explore lesson ChemistryLessonCarbon and Silicon Compared
Carbon and silicon both belong to Group 14 and often make four bonds. Yet carbon forms a huge range of stable chains and double bonds, while familiar silicon dioxide is an…
Explore lesson ChemistryLessonCarbon and Silicon Contrasted
Carbon and silicon each have four valence electrons, yet carbon forms countless stable molecules with C=C and C≡C bonds, while silicon's familiar compounds often build Si–O…
Explore lesson ChemistryLessonCarbon Bonding Beyond the Basics
Carbon compounds vary enormously because carbon usually makes four covalent bonds and can bond repeatedly to itself. A formula tells how many atoms are present, but it does not…
Explore lesson ChemistryLabCarbon catenation
Carbon atoms link into chains and branches. See every chain isomer of an alkane.
Explore lesson ChemistryLessonCarbon Compound Formula Audit
An organic formula can look plausible yet contain an impossible bond count or an omitted hydrogen. A structured audit checks each atom's ordinary valence, totals the molecular…
Explore lesson ChemistryLessonCarbon Compounds in Everyday Life
Look around you right now. The screen you are reading, the clothes you are wearing, the food in your lunchbox and the fuel that delivered it almost certainly all contain carbon…
Explore lesson ChemistryLessonCarbon Compounds Integrated Problems
An integrated organic problem may begin with a molecular formula, ask for isomers, require a name and finish with a balanced reaction or mole calculation. The safest route is to…
Explore lesson ChemistryCollectionCarbon Compounds: Introduction
Study Carbon Compounds: Introduction with 40 free lessons, worked examples, and answered practice questions.
Explore lesson ChemistryLessonCarbon Compounds: Unit Review
This unit began with a single question: why is carbon special? The answer — four covalent bonds and an outstanding ability to bond to itself — led us through chains and rings…
Explore lesson ChemistryLessonCarbon Dioxide and Double-Bond Counting
Carbon dioxide is often printed as O=C=O, but that compact formula hides a full electron-accounting argument. Why two double bonds? Why are there lone pairs on oxygen but none on…
Explore lesson ChemistryLessonCarbon Dioxide as a Chemical Feedstock
Carbon dioxide is often treated only as an emission, but its carbon atom can enter chemicals, polymers, carbonates and fuels. Using a captured CO₂ stream can replace another…
Explore lesson ChemistryLessonCarbon Dioxide in the Atmosphere
Carbon dioxide makes up only about four molecules in every ten thousand in the air, yet life on Earth depends on it. Every plant builds its body from carbon dioxide taken from…
Explore lesson ChemistryLessonCarbon Dioxide Reduction Selectivity
An electrode supplied with CO₂ and electrons can make several carbon products while also reducing water or protons to H₂. A high total current may therefore mean rapid hydrogen…
Explore lesson ChemistryLessonCarbon Dioxide Versus Water Polarity
CO₂ and H₂O each have two bonds to oxygen-containing ends in familiar diagrams, and each relevant bond is polar. Yet CO₂ has no permanent molecular dipole in its equilibrium…
Explore lesson ChemistryLessonCarbon Monoxide and Carbon Dioxide
Carbon monoxide and carbon dioxide differ by one oxygen atom, but they have sharply different chemical and biological behavior. CO is a toxic gas and useful ligand or reducing…
Explore lesson ChemistryLessonCarbon Monoxide and Competitive Heme Binding
Carbon monoxide is a small, colourless, odourless gas that binds to exactly the same site as oxygen: the ferrous iron of a haem group. Because it binds far more tightly, even a…
Explore lesson ChemistryLessonCarbon Monoxide and Particulates
When a fuel burns with plenty of oxygen, its carbon ends up as carbon dioxide and its hydrogen as water. But flames are often starved of oxygen: a gas boiler with a blocked flue…
Explore lesson ChemistryLessonCarbon Monoxide Migratory Insertion
Carbon monoxide can become the carbonyl carbon of an organic product when a metal-bound alkyl group and a coordinated CO combine. This elementary pattern is called CO migratory…
Explore lesson ChemistryLessonCarbon Monoxide: The Silent Hazard
Most dangerous gases give some warning: chlorine smells sharp, smoke stings the eyes, and natural gas has a smell deliberately added so that leaks are noticed. Carbon monoxide…
Explore lesson ChemistryLessonCarbon Nanomaterials
Carbon nanomaterials make an especially clear lesson in structure–property relationships. The same element can form a closed molecular cage, a long hollow tube or an atomically…
Explore lesson ChemistryLessonCarbon Nanotubes
A carbon nanotube is a narrow cylinder built from a hexagonal carbon network. Its small diameter and long axis give it an unusually anisotropic structure: electrons and…
Explore lesson ChemistryLessonCarbon Radicals and Their Stability
A carbon radical has an unpaired electron, usually shown by a dot. It is produced in many homolytic pathways and can react by one-electron steps or bond formation. It is neither…
Explore lesson ChemistryLessonCarbon Tetravalence and Chain Formation
Carbon's ability to form stable C–C connections lets organic structures vary far beyond a short list of molecules. A chain may branch, close into a ring or include a multiple…
Explore lesson ChemistryLessonCarbon-13 NMR Spectroscopy
¹H NMR describes the hydrogen atoms of a molecule, but the carbon skeleton is the real backbone of organic chemistry. Carbon-13 NMR looks directly at the carbon atoms, including…
Explore lesson ChemistryLessonCarbon-14 Dating and Its Scope
Carbon-14 dating is a radiometric method for suitable carbon-bearing material from once-living organisms. It works because living organisms exchange carbon with their…
Explore lesson ChemistryLessonCarbon–Carbon Bonding and Catenation
Catenation is the ability of an element to form bonds to atoms of the same element. Carbon does this extensively, making chains, branches and rings that support organic…
Explore lesson ChemistryLessonCarbon–Halogen Bond Polarity
A halogen bonded to carbon draws bonding electron density toward itself because halogens are more electronegative than carbon. This creates a polar C–X bond with a partially…
Explore lesson ChemistryLessonCarbon's Electron Arrangement and Valency
Every property of carbon that makes it special starts with its electrons. A carbon atom has six electrons, arranged 2,4: two in the inner shell and four in the outer shell. Four…
Explore lesson ChemistryLabCarbonate + acid gas evolution
An acid reacts with a carbonate and fizzes out carbon dioxide.
Explore lesson ChemistryLessonCarbonate Buffer Design
Carbonate buffers are cheap, non-toxic and useful in the alkaline range, where few simple alternatives exist. They are built on the second dissociation of carbonic acid, HCO₃⁻ ⇌…
Explore lesson ChemistryLessonCarbonate Ion and Resonance
Carbonate occurs in limestone, chalk and many salts. Its formula CO₃²⁻ tells us it carries two negative charge units, but a single Lewis drawing can misleadingly place both on…
Explore lesson ChemistryLessonCarbonate System Equilibria
The carbonate system is more than a textbook diprotic acid. Dissolved CO₂ can exchange with a gas phase, a small portion hydrates to carbonic acid, and proton-transfer equilibria…
Explore lesson ChemistryLessonCarbonate–Acid Carbon Dioxide Calculations
Carbonates often fizz with acid because carbon dioxide forms. The visible bubbles are useful evidence, but a quantitative result needs the carbonate formula, acid amount and…
Explore lesson ChemistryLessonCarbonyl Addition Stereochemistry
Nucleophilic addition changes a flat carbonyl carbon into a tetrahedral centre. If that centre ends with four different substituents, attack from the two sides of the original…
Explore lesson ChemistryLessonCarbonyl Chemistry: Checkpoint Review
Carbonyl chemistry is easier to master as a connected set of decisions than as a long list of named reactions. The first question is what is attached to carbonyl carbon; the…
Explore lesson ChemistryLessonCarbonyl Compounds Review
Aldehydes, ketones and carboxylic acids all contain a carbonyl bond, yet the atoms attached to carbonyl carbon produce very different behaviour. A comparison by structure is more…
Explore lesson ChemistryLessonCarbonyl Geometry and Polarity
The carbonyl carbon is approximately trigonal planar before addition because it has three sigma-bond directions and a pi bond to oxygen. Oxygen draws bonding electron density…
Explore lesson ChemistryLessonCarbonyl Infrared Spectroscopy
Infrared spectroscopy is the quickest way to "ask" a metal carbonyl how electron-rich its metal centre is. The C–O stretch absorbs in a region of the spectrum that is almost…
Explore lesson ChemistryLessonCarbonyl Photochemistry: Norrish Type I and II
Carbonyl compounds absorb light through electronic transitions associated with the C=O group. Excitation can lead to bond cleavage or hydrogen transfer that is uncommon from the…
Explore lesson ChemistryLessonCarbonyl Polarity and Addition
The C=O bond is a central reaction site in organic chemistry because oxygen pulls electron density toward itself. The carbonyl carbon becomes partially positive and can accept an…
Explore lesson ChemistryLessonCarbonyl Reactivity: Aldehydes, Ketones and Acid Derivatives
All carbonyl compounds display a polarised C=O bond, yet they do not react identically. Ethanal can be attacked and protonated to an addition product, whereas an acyl chloride…
Explore lesson ChemistryLessonCarbonyl Reduction Pathways
An aldehyde or ketone can be converted back to an alcohol by reduction. A hydride reagent delivers H with a bonding electron pair to the electrophilic carbonyl carbon, and a…
Explore lesson ChemistryLessonCarboxylate Salts and Acid-Base Reactions
Carboxylic acids are weak acids, but they are strong enough to react with every common laboratory base, including the mild hydrogencarbonate ion that phenols and alcohols leave…
Explore lesson ChemistryLessonCarboxylic Acid Derivative Interconversions
Carboxylic acids, acid chlorides, anhydrides, esters and amides share an acyl carbon, R–C(=O)–, but differ in the group attached to it. That attached group controls how readily a…
Explore lesson ChemistryLessonCarboxylic Acid Derivative Reactivity
Aldehydes and ketones often undergo nucleophilic addition because they have no ordinary leaving group attached to the carbonyl carbon. Carboxylic acid derivatives have an acyl…
Explore lesson ChemistryLessonCarboxylic Acid Derivatives Overview
Replace the OH of a carboxylic acid with another electronegative group and you get a carboxylic acid derivative. Acid chlorides, acid anhydrides, esters and amides all contain…
Explore lesson ChemistryLessonCarboxylic Acid Functional Group
The –COOH group combines a carbonyl, C=O, and an O–H bond on the same carbon. Together they form the carboxyl group. The hydrogens of an organic molecule are not all equally…
Explore lesson ChemistryLessonCarboxylic Acid Integrated Problems
Carboxylic-acid problems often combine naming, proton transfer, derivative formation and equilibrium. The same carbon skeleton can appear as a neutral acid, carboxylate salt…
Explore lesson ChemistryLessonCarboxylic Acid Structure and Naming
Vinegar, sour milk, the sting of an ant and the smell of rancid butter all come from carboxylic acids. These compounds contain the carboxyl group, –COOH, which combines a…
Explore lesson ChemistryLessonCarrier Concentration and the Law of Mass Action
Doping silicon with donor atoms can raise its electron concentration by many orders of magnitude. Where do the holes go? They do not all disappear by a literal one-to-one…
Explore lesson ChemistryLessonCarrier Mobility and Conductivity
Carrier concentration tells how many electrons or holes can conduct; mobility tells how effectively they respond to an electric field. Two semiconductor samples can have the same…
Explore lesson ChemistryLessonCase Study: Analysing a Real Sample
Imagine a community water sample suspected of containing elevated chloride and a trace volatile solvent. The two analytes pose different analytical questions: chloride is…
Explore lesson ChemistryLessonCase Study: Greener Ibuprofen Synthesis
Ibuprofen manufacture is a standard case study because a new route made the same medicine in fewer steps and with much less stoichiometric waste. The BHC Company process replaced…
Explore lesson ChemistryLessonCase Study: Pericyclic Steps in Natural Product Synthesis
Natural products often contain fused, bridged or densely substituted rings. A Diels–Alder step can create two carbon–carbon bonds, one ring and several relative stereochemical…
Explore lesson ChemistryLessonCase Study: Planning the Synthesis of Ibuprofen
Ibuprofen provides a concrete case in which the same target can be made by routes with very different material demands. Its aromatic ring bears an isobutyl group and a…
Explore lesson ChemistryLessonCase Study: Retrosynthesis of a Drug Molecule
Aspirin provides a compact but realistic retrosynthesis case because its structure contains two oxygen-containing functions with different roles: a carboxylic acid attached to an…
Explore lesson ChemistryLabCatalysed decomposition
Hydrogen peroxide decomposes to water and oxygen. Compare the rate with and without a catalyst.
Explore lesson ChemistryLessonCatalysed Decomposition of Hydrogen Peroxide
Hydrogen peroxide can decompose into water and oxygen. The equation is simple, but the reaction rate can vary greatly. A suitable catalyst speeds the process by changing the…
Explore lesson ChemistryLessonCatalysis and Rate Laws
A catalyst speeds up a reaction without being consumed overall, but it is not a spectator. It enters the mechanism, forms intermediates and is regenerated at the end of each…
Explore lesson ChemistryLessonCatalysis by Transition Metals
Transition metals and their compounds catalyse many reactions because they can bind substrates, exchange ligands and, in some cycles, change oxidation state. These capabilities…
Explore lesson ChemistryLessonCatalysis Versus Stoichiometric Reagents
A stoichiometric reagent is used up as the reaction advances; a catalyst can participate repeatedly. Replacing a stoichiometric metal reagent with a small amount of selective…
Explore lesson ChemistryLessonCatalyst Deactivation and Recyclability
A catalyst can give excellent initial conversion and still be impractical if its activity vanishes after a few turnovers. Organometallic catalysts face several failure modes: the…
Explore lesson ChemistryLessonCatalyst Deactivation and Regeneration
A catalyst can speed a reaction without being consumed in the ideal reaction equation, but an industrial catalyst does not last forever. Its active sites can be blocked…
Explore lesson ChemistryLessonCatalyst Deactivation Pathways
A catalyst can be impressive in its first minute and poor after a day. Activity may decline because the number of sites falls, the intrinsic activity of each site changes or…
Explore lesson ChemistryCollectionCatalyst Design and Comparison
Study Catalyst Design and Comparison with 40 free lessons, worked examples, and answered practice questions.
Explore lesson ChemistryLessonCatalyst Design and Comparison: Unit Review
This unit began by asking what a catalyst must do: make the right product fast, repeatedly, within a real process. Mechanisms, binding-energy descriptors and volcano plots guide…
Explore lesson ChemistryLessonCatalyst Design: Defining the Target
“Best catalyst” has no meaning until the reaction, desired product and operating context are specified. A material that reacts quickly can waste most feedstock on by-products. A…
Explore lesson ChemistryLessonCatalyst Regeneration and Recycling
A catalyst can be recovered, washed and reused; it may also need a deliberate regeneration treatment to remove deposits or restore a chemical state. Neither procedure proves that…
Explore lesson ChemistryLessonCatalyst Selection for a Process
The catalyst with the fastest initial rate is not necessarily the best process catalyst. A production decision asks how much on-specification product can be delivered over time…
Explore lesson ChemistryLessonCatalyst Selectivity and Poisoning
A catalyst may convert reactant quickly but produce the wrong product, or give the right product initially and fail after hours of operation. Therefore catalytic performance has…
Explore lesson ChemistryLessonCatalyst Selectivity from Competing Paths
A catalyst need not produce only one product. At a branching intermediate, two elementary pathways compete; afterward, a desired product may react again before it leaves the…
Explore lesson ChemistryLessonCatalyst Supports and Metal–Support Interactions
A support is often described as an inert carrier, but it can control metal-particle size, anchor isolated atoms, exchange charge, supply reactive species or cover the metal.…
Explore lesson ChemistryLessonCatalysts and Alternative Pathways
A catalyst changes how a reaction proceeds, commonly offering a pathway with a lower effective activation barrier. It can make a reaction reach equilibrium much faster, but at a…
Explore lesson ChemistryLessonCatalysts and Equilibrium Position
A catalyst can make a reversible reaction reach equilibrium much sooner, but it does not make the equilibrium composition more product-rich at the same temperature. The forward…
Explore lesson ChemistryLessonCatalytic Carbonylation
Carbon monoxide is a cheap one-carbon building block, available from synthesis gas. Transition metals can stitch it into organic molecules, turning an alkyl group into an acyl…
Explore lesson ChemistryLessonCatalytic Cracking with Zeolites
A refinery may need more smaller hydrocarbons than crude-oil distillation supplies. Catalytic cracking converts heavier feed into a useful mixture, often including gasoline-range…
Explore lesson ChemistryLabCatalytic cycle
An organometallic catalytic cycle, with the metal’s oxidation state and electron count at each step.
Explore lesson ChemistryLessonCatalytic Cycles and Turnover
Organometallic catalysts perform the same chemical task thousands or millions of times. The standard way to describe this is a catalytic cycle: a loop of elementary steps…
Explore lesson ChemistryLessonCatalytic Efficiency and Catalytic Perfection
An enzyme's k_cat tells us how rapidly a saturated site turns over; K_m tells us where the rate curve reaches half saturation. Their ratio k_cat/K_m combines these features and…
Explore lesson ChemistryLessonCatalytic Efficiency and the Diffusion Limit
An enzyme with a high turnover number is not necessarily effective when substrate is scarce. At low concentration, molecules must first find and bind an enzyme before chemistry…
Explore lesson ChemistryLessonCatalytic Hydrogenation
Hydrogen gas can convert an alkene to an alkane, but the uncatalysed reaction is normally too slow under mild conditions. A metal such as palladium or platinum provides a surface…
Explore lesson ChemistryLessonCatalytic Ozone Destruction Cycles
The Chapman mechanism alone predicts about twice as much ozone as we observe. The missing loss comes from trace radicals — present at parts per billion or less — that catalyse…
Explore lesson ChemistryLessonCatalytic Reaction Networks
A catalyst participates in a cycle and returns to a form able to react again. In heterogeneous catalysis, the cycle runs across occupied and vacant surface sites. A reaction…
Explore lesson ChemistryLessonCatalytic Reforming and Isomerisation
Cracking makes smaller molecules, but a refinery can also improve a fuel stream by changing molecular structure. Straight-chain hydrocarbons in naphtha are often less useful for…
Explore lesson ChemistryLessonCatalytic Strategies in Enzymes
Lowering an activation barrier is a general description of catalysis, but an exam mechanism must identify the chemistry that does it. Enzyme active sites use a small toolkit in…
Explore lesson ChemistryLessonCatenation and Allotropy
Carbon's ability to link to itself helps produce both countless molecules and distinct elemental solids. Two related ideas must be kept separate. Catenation concerns…
Explore lesson ChemistryLessonCathode and Anode in Electrolysis
Cathode and anode names are defined by reactions, not permanently by plus or minus signs. Reduction occurs at a cathode and oxidation at an anode in every electrochemical cell.…
Explore lesson ChemistryLessonCathode Rays
Cathode rays played a central role in the discovery of the electron. Their name reflects the negative electrode associated with their production in historical discharge tubes.…
Explore lesson ChemistryLessonCation Analysis: Putting It Together
Identifying one cation from a list is simpler than identifying several in one solution. A mixed sample can produce overlapping precipitate colours, one ion can mask another, and…
Explore lesson ChemistryLessonCation and Anion Patterns by Group
Group patterns make many ionic formulas easier to predict. Group-one metals commonly make +1 ions, group-two metals +2, group-17 non-metals −1 and group-16 non-metals −2 in…
Explore lesson ChemistryLessonCation and Anion Sizes
Forming an ion changes an atom's electron count while leaving its proton count unchanged. A simple cation is often smaller than its parent neutral atom; a simple anion is often…
Explore lesson ChemistryLessonCations, Anions and Parent-Atom Size
Comparing an atom with its own ion holds the nucleus fixed while changing electron count. Sodium loses its outer 3s electron to become Na⁺; chlorine gains an electron to become…
Explore lesson ChemistryLessonCell EMF from Reduction Potentials
The standard voltage of a galvanic cell comes from a difference between two standard reduction potentials. The reliable formula is E°cell = E°red,cathode − E°red,anode. The anode…
Explore lesson ChemistryLessonCell Notation
Cell notation compresses an electrochemical diagram into a sequence of phases and interfaces. A common galvanic convention writes the anode on the left, the cathode on the right…
Explore lesson ChemistryLessonCell Voltage and Gibbs Energy
The equation ΔG=−nFE is often memorized, but its meaning is richer than a sign rule. It connects thermodynamic work per reaction extent to charge moved across a potential…
Explore lesson ChemistryLessonCentrifugation
Sedimentation works, but it can be painfully slow: fine clay may take days to settle and the particles in blood never settle properly on their own. Scientists speed things up by…
Explore lesson ChemistryLessonCFSE and Hydration Enthalpies
Hydrating a divalent transition-metal ion brings water molecules into its coordination sphere. If all ions differed only smoothly in size, hydration enthalpy would change…
Explore lesson ChemistryLessonCFSE and Ionic Radii Trends
Across a row of similarly charged metal ions, increasing nuclear charge tends to draw electrons inward, suggesting a smooth decrease in ionic radius. Transition-metal M²⁺ radii…
Explore lesson ChemistryLessonCFSE and Kinetic Inertness
A coordination compound can be thermodynamically favoured yet exchange ligands quickly, or thermodynamically disfavoured yet persist for a long time. The distinction is between…
Explore lesson ChemistryLessonCFSE and Lattice Energies
Simple electrostatic models predict a reasonably smooth lattice-energy trend when similarly charged metal ions become smaller across a series. Transition-metal halides may depart…
Explore lesson ChemistryLessonCFSE and Spinel Structures
A spinel oxide has formula AB₂O₄ and contains both tetrahedral and octahedral positions among its oxygen ions. Which cation occupies which site changes magnetic, electrical and…
Explore lesson ChemistryLessonChadwick Discovers the Neutron
Once the nucleus was recognised, another problem remained. Its positive charge indicated how many protons it contained, yet those protons often accounted for only about half its…
Explore lesson ChemistryLessonChain and Position Isomerism — Carbon and its Compounds
Constitutional isomers share a molecular formula but differ in atom connectivity. Chain isomers have different carbon skeletons, while position isomers retain the basic skeleton…
Explore lesson ChemistryLessonChain and Position Isomerism — Organic Conversions, Isomerism and Reasoning
The same atoms can form a straight chain, a branched chain or a chain with a functional group in a different position. These are common constitutional isomers in conversion…
Explore lesson ChemistryLabChain reaction (ignition)
Chain branching in H₂ + O₂: when radicals multiply faster than they are lost, the mixture explodes.
Explore lesson ChemistryLessonChain Reaction Kinetics
An overall reaction can proceed through a small number of reactive intermediates that are regenerated repeatedly. One newly made radical may drive many product-forming cycles…
Explore lesson ChemistryLessonChain Shortening by Oxidative Cleavage
Ozonolysis cuts a carbon–carbon double bond and turns each former alkene carbon into a carbonyl carbon after a suitable work-up. An open-chain alkene often becomes two smaller…
Explore lesson ChemistryLessonChain-Growth Polymerisation: Principles
Chain growth builds polymer through a small population of reactive chain ends. Initiation creates those ends, propagation adds monomer repeatedly, and termination or transfer…
Explore lesson ChemistryLessonChain-Growth Polymerization
Ethene can become polyethylene through repeated addition to a reactive chain end. Unlike step growth, a long chain can form while much monomer remains because propagation can be…
Explore lesson ChemistryLessonChain-Reaction Kinetics
Some reactions proceed far faster than their slowest elementary step would suggest. The explanation is a chain mechanism: a single reactive intermediate, once formed, passes…
Explore lesson ChemistryLessonChain, Position and Functional Isomerism
Constitutional isomers can be grouped by the most visible connectivity change. Chain isomers differ in skeleton branching, position isomers place a group or bond at different…
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