Chemistry Unit 2: Notes2.1-Shapes of molecules and ionsElectron-pair repulsion theory:The shape of a molecule or an ion depends on thenumber of electron pairs that surround the atom. The electron pairs repel each otherso stay far apart from each other.Linear:2 electron pairs, 180bond angles (e.g. BeCl2, CO2)Trigonal Planar:3 electron pairs, 120bond angles (e.g. BCl3)Bent:2 electron pairs, 1 lone pair,Tetrahedral:4 electron pairs, 109.5bond angles (e.g. CH4, NH4+)Trigonal Pyramidal:3 electron pairs, 1 lone pair, 107bond angles betweenelectron pairs (e.g. NH3)Bent:2 electron pairs, 2 lone pairs, 104.5bond angles between electron pairs (e.g.H20)Trigonal bipyramidal:5 electron pairs, 90 and 120 bond angles (e.g. PCl5)Octahedral:6 electron pairs, 90and 180bond angles (e.g. SF6)Lone pairs and double/triple bondsrepel more than electron pairs hence thedifferences in angles even with 4/ 3 bonds.Alkanes:Tetrahedral due to all bond angles being 109.5 due to carbon forming 4bonds.Alkenes:Bonds around the double bond are trigonal planar but due to the doublebond the bond angles can range from 121-118.Alcohols:Hydrocarbon chain is tetrahedral so bond angles are 109.5. C-O-H bondis a bent molecule so is 104.5.Carboxylic acids:-COOH group around the carbon is trigonal planar so 120.Haloalkanes:Tetrahedral as halogen bonds dont affect bond angles. Same asalkanesCarbonyls:CHO/C=0 bonds around the carbon are trigonal planar (120).Diamond:Tetrahedral due to 4 carbon electron pairs being formed.Graphite:Trigonal planar as only 3 carbon electron pairs are formed. Goodconductor due to weak London forcesFullerene:Spherical molecule made up of about 60 carbon atoms which candissolve in petrol and is a good conductor.Nanotubes:Tube-like cage structure made up of 12 membered rings that can beused to carry drugs to target body cells.2.2-intermediate bonding and bond polarityElectronegativity:A measure of the attraction of an atom in a molecule for a pair ofelectrons in a covalent bond.Fluorineis themost electronegativeas it has theleast shieldingwhilst still havingalarge number of protonsso has agreater pull.Covalent bond: Shared electrons.Ionic bond:Loss of electrons by metal and gainof electrons by non-metal.Bothare two extremes of the spectrum.

Differences between electronegativitiesof atoms can determine what percentageof each character (covalent or Ionic) they are. Looking at theelectron cloudaroundthe bond can also determine their character.Polar covalent bondswill have aneven spread of chargewhereasIonic bondswill show adistortionin the electroncloud around one atom.Non-symmetrical moleculestendto bepolarso will produce a cleardipole(e.g. Trichloromethane) with aknownpolaritymeasured indipolemoment(Debye, D).Symmetrical moleculesarenon-polardue to thedipoles cancelling.(e.g. CO2)2.3-Intermolecular forcesTypes of Intermolecular forcesPermanent dipoles:Polar molecules only. Negative dipole attracted to the Positivedipole and vice versa. 100x weaker than covalent bonding.London forces:Electrons distributed around the nucleus change so more electronsare distributed around one end. This induces another atom thats near it to do thesame. So a weak temporary bonding forms between the two atoms. Is a weak forcebut strength does depend on the size of the electron cloud. More electrons=moredelocalisation=more London forces.Hydrogen bonding:Hydrogen attached to a very electronegative element (e.g.fluorine, oxygen and nitrogen.). This is the strongest intermolecular force.Boiling temperature trends (determined by intermolecular forces)Alkanes with increasing chain length:Increasing boiling temperature due toincreasing London forces with the increase in the number of electrons.Branching in the carbon chain:The boiling temperature decreases. This isbecause the side chains interfere with the packing of the molecule. Molecules cantform many intermolecular forces.Alcohols:Have hydrogen bonds present so have high boiling temperatures. Waterhas a higher boiling temperature than alcohols as it can form double the amount ofHydrogen bonds.Hydrogen halides down the period:Fluorine is highly electronegative so has avery large boiling temperature compared to the rest which from chlorine starts lowaround -80and then gradually increases due to increased dipole-dipole interactionsfrom increased number of electrons.Solubility trendsA solution is made up of a solute and a solvent. Table below shows thesolubility of different substances. Ketone is unusual in that it can dissolve inboth water and organic solvents as it has both of the functional groups.Formula Description E.g.PolarAB Linear COHA Single H HClAxOH OH at one end C2H5OHNxAyN at one end NH3Non-polarA2All elements O2CxAyCarboncompoundsCO2

2.4-RedoxOxidation no.:amount of charge due to no. of electrons.RulesAtom Oxidation no.Elements 0Uncombined ionIts chargeMolecule total 0Fluorine -1Hydrogen +1 (except metal hydrides=-1)Oxygen -2 (except peroxides=-1 and withfluorine=positive no.)Chlorine -1 (except with oxygen orfluorine=positive no.)Group 1, 2, 3 +1, +2, +3 respectivelyOILRIG:Oxidation is loss, Reduction is gain.Reducing agent:Reduces another substance whilst being oxidised itselfOxidising agent:Oxidises a substance whilst being reduced itself.Reduction half equation:Cl2(g)+ 2e-2Cl-(aq)Oxidation half equation:2I-(aq)I2(s)+ 2e-Key half equations:02(g)+4e-202-(s)2H20(l)+2e-2OH-(aq)+H2(g)2H+(aq)+2e-H2(g)Displacement:One substance replaces another in a reaction.HighlyPolarsolidsPolarorganicsubstancesNon-polarsolidsIoniccompound(e.g.NaCl)Non-polarliquidsWatersoluble soluble insoluble Soluble(Hydrationenthalpy)Hexaneinsoluble insoluble solublePolarliquidsImmiscible(forms twoseparatelayers)Non-polarliquidsmiscible

Disproportionation:Where a substance is both oxidised and reduced in a reaction.2.5-Periodic TableGroup 2Trend in 1stIonisation energy:Decreases down the group due to increasing atomicradius where the outer electrons are further away so less energy is needed toremove an electron. Forms 2+ ions easilyReactions- With Oxygen:Burns brightly to produce a metal oxide with increasingreactivity down the group.With Chlorine:Solid metal chloride formed. Also has an increase in reactivity.With Water:Increasing reactivity down group. Beryllium has no reaction,Magnesium only reacts with steam to produce a magnesium oxide and the rest reactwith cold water to produce metal hydroxides.Oxides with Water:Increasing reactivity. Beryllium and magnesium only reactslightly, Calcium fizzes to produce calcium hydroxide (slaking lime), and strontiumand Barium react in a similar way.Oxides/Hydroxides with Dilute Acids:Forms a salt and water. E.g. CaCl2+ H2O orCa(NO3)2+H2OFlame Testing:Place nichrome wire inconcentrated HCl then heat in a bunsen flame toclean. Colours of flames are shown in table.SolubilityOf hydroxides:Increases down groupOf Sulphates:Decreases down groupThermal StabilityOf Nitrates:Decreases down group 1 due to weaker charge of attraction. Group 1are more stable than group 2 apart from lithium due to larger charge.2NaNO32NaNO2+O2, 4liNO32Li2O+4NO2+O2, 2Mg(NO3)22MgO+4NO2+O2Of Carbonates:More stable as you go down the group as cations get bigger sothere is a more polarising effect on the carbonate.Common Oxidising Agents Common Reducing agentsO2+4e-2O2-M Mn++e-(metal)Cl2+2e-2Cl-Fe2+Fe3++e-Br2+2e-2Br-2I-I2+2e-I2+2e-2I-2S2O32-S4O62-+2e-Fe3++e-Fe2+C2O42-2CO2+2e-2H++2e-H2H2O2O2+2H++2e-Mn04-+8e-Mn2++4H2O S032-+H2O SO42-+2H++2e-Cr2O72-+14H++6e-2Cr3++7H2O2H2SO4+2e-SO42-+2H2O+SO2Cation Flame ColourLithiumRedSodiumYellowPotassiumLilacMagnesiumNo colourCalciumOrange/RedStrontiumRedBariumPale Green

Group7-HalogensSolubilityIn Water:Chlorine forms chlorine water which is colourless, Bromine water isOrange; Iodine isnt soluble in water as it needs I3-ions so instead, it dissolves inPotassium iodide which is Brown.In organic solvents:As halogens are non-polar, they dissolve more easily inhydrocarbon solvents than water. Chlorine= Pale yellow, Bromine=Brown,Iodine=PurpleOxidisation reactionsHalogens are strong oxidising agents,With metals:Form salts. 2Fe+3Cl22FeCl3, Fe+I2FeI2With Hydrogen:Decreasing reactivity down group. Chlorine explodes whereasBromine and Iodine need 300C and Platinum catalyst.With Phosphorus:Chorine forms a chloride (III) then a chloride (V).With Iron Chloride:Green iron (II) chloride becomes oxidised to brown iron (III)chloride.Chlorine is a stronger oxidising agent than iodine:2KI-+Cl22KCl+I2Sulphuric acid oxidises halides and halogens with increasing vigour down thegroup.Hydrogen Halides are covalent but become increasingly ionic as you go up thegroupHydrogen Halides and Ammonia:NH3+HCl NH4ClDisproportionation reactionsWith cold dilute Alkali:Cl2+2OH-Cl-+ClO-+H2OWith warm Alkali:3ClO-2Cl-+ClO3-Testing for halogensSilver halides:AgCl-White precipitate which is soluble in ammonia,AgBr-Creamprecipitate which is soluble in ammonia,AgI-Yellow precipitate which is insoluble inammonia.Concentrated sulphuric acid and glass rod with ammonia:Chlorine=whitefumes, white smoke. Bromine=white and orange fumes, white smoke. Iodine=Whiteand purple fumes, white smoke.2.6-KineticsRate of reaction:Speed with which reactants disappear and products are formedfor a particular reaction.Decreased rate=Decreased yieldFactors in rate of reaction

Concentration:Affects number of collisions due to change in number of particles ina given volume.Temperature:Affects activation energy due to faster moving particles with moresuccessful collisions.Pressure:Affects number of collisions due to change in number of particles in agiven volume.Surface area:Affects the number of particles open to contact.Catalysts:Changes the rate of reaction without being used up or undergoing anypermanent changes by lowering the activation energy through forming an activatedcomplex. Industrial processes rely on catalysts to save money, energy andresources.Collision theory:In order for a reaction to happen, colliding particles need to be inthe right orientation and have enough energy. Rate of reaction depends on this.Maxwell-Boltzmann model-models the distribution of molecular energies sochanges in concentration, temperature or pressure can be calculated to predict therate of reaction. E.g. As the temperature rises, the graph flattens so there are agreater proportion of particles moving fast enough to overcome activation energy.Activation energy:Minimum energy required for a reaction to take place.2.7-Chemical EquilibriaDynamic Equilibria:Two opposing processes that occur at the same rate so haveconstant macroscopic properties.Le Chateliers principle:Whenever a system in dynamic equilibrium is disturbed, ittends to respond in opposition to the disturbance in order to restore equilibrium.Increase in Temperature:Moves in the endothermic direction.Increase in Pressure:Moves to the side with the fewest number of moles.Increase in Reactants:Moves to the other side as more products are formed.Increase rate.Equilibria Reactions:N2O42NO2, ICl+ICl2ICl3Haber Process:Production of ammonia (Exothermic reaction). Atom economy=100% as all reactants are used (Recycled).2.8-Organic ChemistryAlcoholsFunctional group:-OH (Methanol, Ethanol, Propan-1-ol)Primary Alcohol:1 carbon attached to the carbon with the functional group on it.Secondary Alcohol:2 carbons attached.Tertiary alcohol:3 carbons attached.Combustion:Produces carbon dioxide and waterReaction with sodium:2Na+2C2H5OH 2C2H5O-Na++H2,effervescence, forms awhite precipitate.

Reaction with PCl5:Reaction produces a chlorine haloalkane, POCl3and HCl gas(misty white fumes that turn damp blue litmus paper red).Oxidation using acidified potassium dichromate (toxic, carcinogen):Primaryalcohols when oxidised, produce aldehydes, then carboxylic acids if refluxed.Secondary alcohols produce ketones which cant be oxidised further. Tertiaryalcohols show no reaction.When making ethanoic acid, add ethanol carefully to dichromate as it couldevaporate if added quickly.Fractional distillationis used to separateethanoic acidfrom the waste product, water.Distillation Apparatus:Reflux Apparatus:HalogenoalkanesFunctional group:R-Cl, R-Br, R-IPrimary Haloalkanes:1 carbon attached to the carbon with the functional group.Most reactive as nucleophiles are more attracted.Secondary Haloalkanes:2 Carbons attached.Tertiary Haloalkanes:3 Carbons attached.Structural isomersarevery commoninhaloalkanes.Achangeinhalogen atompositionmakes ahuge differenceto thepropertiesof themolecule.Halogens react fasterinsubstitution reactionsif thehalogen is attachedto abranched chain.

Metal halidesandconcentrated sulphuric acid should not be usedin thecreation of a haloalkaneas they are very reactive.Reaction with aqueous KOH:Substitution reaction which creates an alcohol as:OH-is attracted to the carbocation after breaking H-Cl.Reaction with alcoholic KOH:Elimination reaction which produces an alkene. KOHattracts H+by acting as a base.Reaction with silver nitrate dissolved in water:Ag+ ion reacts with the halogensto create insoluble products. (See page 6-Silver halides)Reaction with alcoholic ammonia:ammonia acts as a nucleophile which replacesthe halogen atom in a halogenoalkane.Uses of halogenoalkanesAnaesthetic:To put patient in a deep sleep. Chlorine= deep sleep, Fluorine-Carbonbonds= stable molecule so less toxic.Fire retardants:Used to be in fire extinguishers but is now in circuit boards, fabricsand clothing.Refrigerants:Liquid that changes phase to keep things cool.Also used in:Aerosol containers and Insecticides2.9-MechanismsAddition:Two or more substances react to form a single product.Elimination:Small molecule removed from a larger molecule leaving a double bond.Condensation:Addition followed by elimination of H2O or HCl.Substitution:One atom or group of atoms replaced by another atom or group ofatoms.Oxidation:Process where electrons are lost.Reduction:Process where electrons are gained.Hydrolysis:Splitting of a molecule by reaction with H2O.Polymersiation:Joining of small molecules together in a long chain.Homolytic fission:When a bond is broken and both atoms take a single electroneach and form two free radicals.Heterolytic fission:When a bond is broken and both electrons only go to one atomcreating a negative ion and a positive ion. (Carbanion and carbocation.)Free radicals:Has an unpaired electron so is extremely reactive and short lived.E.g. Cl, CH3Electrophile:Atom attracted to an electron-rich centre. Has a positive charge. E.g.H+, Br+Nucleophile:atom attracted to an electron-deficient centre. Has a negative charge.E.g. :NH3-, :OH-Classifying reagentsgivescluestohow a mechanismwilltake place.Bond polaritydetermines whether the centre will beelectron-rich or electron-deficient.Nucleophillic substitution reaction:HalogenoalkanesFree-radical substitution reaction:Alkanes with a halogen.Electrophilic addition reaction:Alkenes with hydrogen or a halogen.

Ozone layer:Formed by O+O2O3. This layer absorbs UV light from the sun butwhen cloud cover and chemicals build up, the spring UV light hitting the cloudscauses any CFCs in them to break up and create free radicals which break down theozone layer into O2molecules.2.10-Mass spectra and IR absorptionMass spectraHighest m/z Value=Parent ion.Most Abundant peak=Base peak.Peaks are produced by the fragmentation of organic molecules.IR absorptionC-H Stretching=2820-3010O-H Stretching=Broad peak at 2500-3750N-H Stretching=3300-3500C=O Stretching=1680-1740C-X Stretching=500-1400There is achange in functional groupswhenalcohol is oxidisedto acarbonylor carboxylic acid.Onlymolecules that change polaritywhen theyvibratecanabsorb IR radiatione.g. Greenhouse gases.Diatomicmoleculescantabsorb IR.2.11-Green ChemistryBio-oilis made for fuel frompyrolysis(heating wheat without burning).Ethanolisproduced fromorganic wasteby converting sugars using bacteria or yeast.Starchhas lots of uses including adhesives, paper bonding, textile fibres, shopping bags,absorption paper, drug and pesticide encapsulation and corrugated card.Catalystsenable a reaction to go under lower temperatures and pressures to saveenergy. Catalysts need to be cheap, very active and produce no by-products.Microwave ovenscan heat reactants more economically. Continuous pulses ofradiation heats up reactants. Electric field occurs which rotates polar molecules andlines them up.Recycling glassandaluminiumsaves energy from having to make more.Waterasa waste product from a reaction in a factory must be treated before being disposedto avoid contaminating the environment. Wasteacidic gasesare removed from therest of the air before it goes into atmosphere.CO2is the most worrying greenhouse gas as it absorbs lots of IR and is abundant inthe atmosphere. The other greenhouse gases arent as abundant.Athropogenic factors: due to activities of human beings.Natural factors: due to natural processes on earth.Carbon neutral: a process that gives out as much CO2as it takes in.

Carbon footprint: a measure of the impact on environment from how muchgreenhouse gas is produced. (Measured in CO2)Petrolisnt carbon neutral due to the slow process of formation of crude oil.Bio-ethanolisnt carbon neutral either as production of biofuel requires energy.Hydrogenisnt carbon neutral as it creates CO2when it is being formed frommethanol.Cl+O3ClO+O2ClO+O3Cl+2O2So in total, 2O33O2due to CFCs so more UV radiation therefore hits earth.Titration calculationsTo find percentage of a metal in an impure substance1. Find the no. of moles using the known concentration and volume of asubstance.2. Use the molar ratio to find the no. of moles in the other reactingsubstance with the metal.3. If divided by 10 fold in question, x no. of moles by 10 to get original no.of moles.4. Original no. of moles x Mr of metal= Mass of metal in grams5. Mass of metal/Total mass x100= Percentage of metal