AS Level Chemistry
Priorities of Oxidation states
Groups 1,2&3 have Oxi no of +1,+2&+3 respectively. Flourine=-1 Hydrogen~+1 Oxygen ~-2 Chlorine~-1
What are steps of mass spectroscopy?
Ionisation, Acceleration, Deflection, Detecting
Deflection
Ions are deflected through magnetic field according to mass (heavy - deflect least)(light - deflect most)
Reducing agent
Is oxidised itself (loses electrons readily) {Ba}
Oxidising agent
Is reduced in itself (gains electrons easily) {Flourine}
Oxidation
Loss of electrons
Mass number
Number of protons and neutrons
Atomic number
Number of protons in an element
What are standard conditions?
0°C (273°K) and 100kPa. Molar volume= 22.1dm3
Primary alcohol
1 alkyl group attached to the carbon attached to OH
Relative masses of P,N and E
1,1, 1/2000 (respectively)
Secondary alcohol
2 alkyl groups attached
What are conditions at RTP?
25°C (298°K) and 100kPa Molar volume= 24dm3
Linear
2=BP 0=LP A=180° 2 electron pairs
Angular (bent)
2=BP 2=LP A=104.5° 4 electron pairs
Tertiary alcohol
3 alkyl groups attached
Pyramidal
3=BP 1=LP A=107° 4 electron pairs
Tetrahedral
4=BP 0=LP A=109.5° 4 electron pairs
Carboxylic acid
A carbonyl group attached to a hydroxyl group and an R group and is ALWAYS AT THE END of the compound. (-oic acid)
Ketone
A carbonyl group attached to two R groups and is in the MIDDLE of the compound. (-one)
Aliphatic
A compound containing carbon and hydrogen in straight chains branched chains or non-aromatic rings.
Saturated hydrocarbons
A compound which all the atoms are linked together by single sigma bonds only.
Aldehyde
A compound with a carbonyl group attached to one hydrogen and one R group and is at the END of the compound. (al)
Alcohol
A compound with an OH functional group present. If its the only functional group then its an alcohol if there are other functional groups then its a hydroxyl group.
Homologous series
A group of compounds: With same general formula Contain same functional group Each member of the group differs by CH2.
Alkane
A hydrocarbon which is saturated (-ane)
Alkene
A hydrocarbon which is unsaturated as it contains at least one double bond (-ene)
Amine
A nitrogen attached to two hydrogen's and an R group at the end of an compound normally found on amino acids
Radical
A particle with an unpaired electron. These are very reactive
Hydrolysis
A reaction where an organic compound is split to form two new products involving water.
What's a precipitate
A solid formed when two liquids react
Substitution with Halide ions
ALL THREE TYPES of alcohols, in the presence of a HALIDE ION (Br-) AND AN ACID (H2SO4). Halide ion replaces OH and the H+ ion in the acid reacts with the OH- form water. C3H7OH + Br- + H+ (NaBr/H2SO4) = C3H7Br + H2O
Acid + Ammonia
Acid + Ammonia 》Ammonium Salt
Acid + Base neutralisation
Acid + Base 》Salt + Water
Acid + Carbonate
Acid + Carbonate 》Salt + Water + Carbon Dioxide
Acid + Metal
Acid + Metal 》Salt + Hydrogen (REDOX)
Water in acid base reactions
Acids & alkalis will not behave as their meant to unless in the presence of water
Esterification
Acids can react with all alcohols to produce an ester and water, but since all these are flammable the heat is normally provided by a water bath or a heating mantle and it also requires CONCENTRATED H2SO4 AND A CATALYST
Halide ion test
Add AgNO3 which forms silver halide which is a ppt. Cl=white (dilute NH3) Br=Cream (Conc NH3) I=Yellow (Insoluble)
Effect of changing Conc on equilibrium
Add acid to Chromate(VI)/dichromate (VI) mixture increase conc of H+ ions, system> chromate + H+=more dichromate + H2O, shifts right. (Orange) Reverse add OH- ions decreases H+ions (H2O) so system> H2O + dichromate=more Chromate shift left (yellow)
Sulfate ion test
Adding Barium Chloride to SO4 (2-) leads to white precipitate.
Halide ion test with NaCl (Ionic equation)
Ag (+)(aq) + Cl (-)(aq) 》AgCl (s)
Solubility of alkanes
Alkanes have low polarity= no attraction to polar molecules of H2O= insoluble in water and form an immiscible layer, but readily dissolve in non-polar substances, as they link through their induced dipole-dipole forces.
Effect of a catalyst
Alter rate without being used in the reaction. Enthalpy change and distribution curve stays the same (unlike temp) but Ea is lower so more particles have more energy than lower Ea. Catalyst find an alternate route to lower the activation energy for a reaction.
Haloalkane
An alkane which contains at least 1 halogen within its structure. (Chloro- , Bromo- , Iodo-,)
Nucleophile
An ion/ molecule that is an electron pair donor and can form a new covalent bond.
Reactivity of haloalkanes
As well as dipoles in carbon-halogen bond, enthalpies also determine rate. C-I bond=weakest requires least energy to break, whereas the C-F bond is the strongest and rarely hydrolysed. The bond enthalpy- DOMINATING FACTOR for determining rate of a haloalkane.
Electronegativity affecting bonds
Atom with greater pull, means electrons not shared between bonds forming slight charges (dipoles). If shape is symmetrical dipoles are cancelled out.
Trends down group
Atomic radius INCREASES- nuclear charge increases & sheilding increases
Trends in 1st Ionisation energy down group
Atomic radius increases= decrease IE. Nuclear charge increases= IE increases. Shielding increases= decrease IE .
Isotopes
Atoms of the same element with different number of neutrons but same number of protons.
Physical properties of alkenes
Bpt&Mpt- INCREASES=Chain Length increases, but lower than corresponding alkane, can't pack together as closely so fewer IMFs. Solubility- Alkenes are non-polar so insoluble in water.
Electrophilic mechanism with Br and an alkene
Br approaches double bond temporary induced dipole formed. Initial curly arrow starts at double bond and points to Br+. Second arrow goes from Br bond to Br-= HETEROLYTIC FISSION. Third arrow lone pair of Br- to carbonium ion= haloalkane. HBr is polar so H+ is the electrophile. Br with ALKENES undergoes HETERLOYTIC FISSION. Br with ALKANES undergoes HOMOLYTIC FISSION.
Effect of surface area
Breaking solid to small pieces= more of the surface is exposed= reaction is quicker, but if it's a big clump it will react slower as less of it would be exposed.
Reactions of alcohols
CO & OH bonds=polar. Combustion>CO2+H2O Oxidation- [O] and H2SO4 (dilute). 1) Aldehyde+ Carboxylic acid. 2) Ketone Elimination/Dehydration- Hot conc H2SO4 or Hot pumice/Al2O3. Lose H2O> Alkene. Substitution with halide ions-Presence of ACID and HALIDE ION (NaBr/H2SO4). Esterification- Acid +alcohol = ESTER + WATER
Carbonate ion test
CO3 (2-)+DILUTE ACID= Salt+Water+CO2. Effervescence of CO2 gas proves carbonate present
Calculating molecular formula
Calculate empirical formula Use empirical formula and relative molecular mass to deduce molecular formula.
Lone pair of electrons
Can form Dative bonds Affect molecule shape Important in chemical reactions. Behave as nucleophile Non bonded pair of electrons
Giant covalent structures
Carbon and Silicon. High mpt&bpt=strong covalent bonds in lattices. Not good conductors no free electrons (except Graphene and Graphite).
Bonding in organic compounds
Carbon- four bonds where two bond to R groups and then to other elements. With hydrogen alkanes are symmetrical and the electronegativity difference isn't great which leads non-polar compounds. Alcohols and halogens disturb symmetry and electronegativity so the molecules become polar and electrons in the sigma bonds move along them to the oxygen or the halogen to stabilise molecule (Inductive Effect).
Heterogeneous catalysts
Catalysts in different states/phase from reactants, e.g. gas reactants and solid catalyst. ADSORBS molecules onto surface. Adsorption weakens bonds, lowering Ea for reaction. Product molecules desorb from surface. (Catalytic poison=no desorption). Transition metals used, Iron= Haber process. Also alloy of Rhodium, Platinum and Palladium in catalytic converters in cars.
Test for halides
Detected by AgNO3 by ppt. Cl=White, Br=Cream, I=Yellow. Then dissolve in NH3: Cl=dilute NH3, Br=Conc NH3, I=nothing happens.
Specialities of water
Due to H bonds: Ice is less dense than liquid as bonds form hexagonal rings= greater volume=lower density. H20 has high mpt&bpt as H bonds between O2 LP=more bonds to break.
Chemical properties of alkenes
Due to double bond can only take part in ADDITIONAL reactions. Weakness of pi bond has low bond enthalpy so breaks forming extra bond for each carbon.
Functional group
Either a structural feature, group of atoms or a single atom. This group determines much of the Chemistry of a compound.
Electron pair repulsion theory
Electron pairs repel each other and shape depends on no of electron pairs. LP-LP>LP-BP>BP-BP
Metallic bond
Electrostatic attraction between delocalised electrons and positive ions in lattice.
Ionic bond
Electrostatic attraction between oppositely charged, which acts in all directions in lattice. Between a metal and non metal
Describe P-orbital
Elongated dumbbell shape vary in charge density with area of greatest concerned increasing with distance from nucleaus due to principle quantum number. Have 3 different orientation of spaces. (x,y,z)
Nth Ionisation energy
Energy required to remove 1 electron feom each (n-1)+ ion in 1 mole of gaseous (n-1)+ ions to form 1 mole of gaseous n+ions
Bond enthalpy
Enthalpy change required to break and seperate 1 mol of bonds in the molecules of a gas so that the resulting gaseous particles exert no forces upon each other. They are specific to a type of bond, they are also averages of the same bond.
Standard enthalpy change of combustion
Enthalpy change when 1 mol of a substance is burned completely in excess oxygen under standard conditions
Standard entalpy change of formation
Enthalpy change when 1 mol of a substance is formed from its elements in their natural state under standard conditions.
Standard enthalpy change of neutralisation
Enthalpy change when 1 mol of water is formed in a reaction between acid and base under standard conditions.
Standard enthalpy change of reaction
Enthalpy change when the amount in moles of the substances in the equation as written react under standard condition.
Avogadro's law
Equal volumes of gases measured at the same temperature and pressure will contain the same number of molecules.
E/Z isomerism
Exists in the presence of a carbon-carbon double bond and each carbon has to be bonded to TWO DIFFERENT ATOMS/GROUPS.
Intermolecular forces (IMFs)
Forces of attraction that occur between ALL molecules.
Salt
Formed when 1 or more Hydrogens of acid is replaced by metal ion or ammonium ion
Chemical properties of group 17
Gain 1 electron=1-Anions. Ease to gain electron decreases Down group as shielding & atomic radius increases. React directly with metals & Non-metals. Displacement (redox) ease increases up group, react in non-polar solvents. Oxidising agents F is best at gaining electrons.
Reduced
Gain of electrons
Ionic compound Properties
Giant ionic lattices. High mpt&bpt- due to electrostatic attraction. Poor conductors (solid)- no mobile ions. Conductors (liquid/molten)- ions are mobile Soluble H2O- polar solvents dissolve polar compunds
Melting point and boiling point trends
Giant metallic and covalent lattices= Strong bonds=high mpt&bpt. Simple covalent molecules= weak IMFs=low mpt&bpt. Mpt&bpt increases from Group 1-13 (Si &C also) Mpt&bpt increases Down group 17 as number of electrons increase.
Exothermic reaction
Gives out heat to surroundings has enthalpy change that's negative. Products are lower than reactants. (Self-warming drinks) (hot packs) Bond breaking is this reaction
Physical properties of group 2
Good conductors when molten/ ions in water not solid with high mpt&bpt. Form colourless ionic (except Be)
Electrical conductivity trends
Group 1,2&3 have mobile electrons and group 13 are the best as they have more delocalised electrons. Other groups don't have these electrons so they can't conduct electricity.
Neutralisation reaction
H+ + OH- = H20
Method 2
Haloalkane + EXCESS NaOH for period of time (FIXED). Then excess alkali neutralised by HNO3. AgNO3 is added and DENSITY of ppt is monitored. (Neutralisation prevent ppt of AgO forming). Repeated for other fixed periods of time.
Trend in rates of hydrolysis of primary haloalkanes Method 1
Haloalkane + H2O +AgNO3 + ethanol in WATER BATH at 60 degrees. H2O= nucleophile (slow reaction) (lone pairs), with time halide ions produced react with Ag+ forming ppt, and monitor production of ppt help deduce rate. Ethanol- aids mixing reagents, they are immiscible together but can dissolve in ethanol. Ethanol~ nucleophile, conditions CAREFULLY CONTOLLED.
CFCs
Haloalkanes WERE used to produce (CFCs). Used as refrigeration units, air conditioners and in aerosols. Needed a liquid with suitable volatility, readily evaporated and re-condensed but un-reactive, non-toxic and non-flammable. Banned by the MONTREAL PROTOCOL 1987. HCFCs were made as they were less stable and but still formed chlorine radicals. Development on HFCs but the nature of products is unknown and could have other harmful effects.
Chain isomerism
Have varying chain lengths like but-1-ene and methyl propene.
Specific heat capacity
Heat required to increase the temperature of 1.0g of the substance by 1°C (1K).
Metallic properties
High mpt&bpt- metallic bond is strong and through whole lattice. Good conductors- mobile charge carriers. Malleable (reshaped) & Ductile (stretched)- metallic bond is in different directions.
Hole in the Ozone layer
Hole due to Cl radicals from Homolytic fission of Cl-C bond in a CFC, attacking ozone layer. Initiation: C-Cl bond breaks due to UV radiation Propagation: Cl¬ + O3 > ¬ClO + O2 and ¬ClO + O > Cl¬ + O2 Net reaction is O3 + O > 2O2 and Cl¬ is regenerated so is pretty much the catalyst for this reaction. Termination: Cl¬+Cl¬>Cl2 or ¬ClO+¬ClO>Cl2O2
IE down groups
IE DECREASES= atomic radius increase=reduce IE. Nuclear charge increases= increasing IE. Shielding increases= IE decrease. Overall IE decreases.
IE across period
IE INCREASES = atomic radius decreases= Increases IE. Nuclear charge increases= increases IE. Shielding stays the same= no effect. Overall IE increases.
Addition polymerisation
Identify the monomer formed Made by the double bond breaking in an alkene and bonding to the same alkene to form a long chain of small molecules of monomers which is a polymer.
Hess' law
If the reaction can take place by more than one route, the enthalpy change for the reaction is the same irrespective of the route taken, provided that the initial and final conditions are the same.
Electronegativity trends
Increases across period Decreases down groups
Arrangement of atoms on the periodic table
Increasing atomic number Periods showing repeating physical/chemical properties Groups have similar chemical properties
Covalent compound properties
Low mpt&bpt-small seperate molecules, with weak IMFs. Poor conductors- no mobile charge carriers (Graphene & Graphite) Soluble in Non polar solvents-they are non polar.
Melting points and boiling points of Alkanes
Low polarity (Van der Waals). As RELATIVE MASS INCREASES bpt INCREASES (number of electrons increasing). ISOMERS with SAME RELATIVE MASS bpt DECREASES as DEGREE OF BRANCHING INCREASES, branches interrupt contact=reduce induced dipoles= low bpt&mpt
Reactions of Group 2
M+2H2O= M(OH)2+H2 M+2Acid(dilute)=Salt+H2 M+Cl2=MCl2(white ppt) 2M+O2=2MO MO+H2O=M+2OH- MCO3 decompose harder down group (thermally). MSO4= white solids, less soluble in H2O down group. Stronger alkali down group= M(OH)2 is more soluble
Relationship between mass, Molar Mass and Moles
M=m/n
Ozone
Made of O3, toxic to humans but is very helpful. It absorbs most of the harmful UV radiation from sun, if reached the Earth's surface then a great increases in sunburn and skin cancer cases.
Propagation
Many steps each maintaining the radical concentration, they are difficult to control and can form complex products 1: CH4 + Cl¬ > HCl + ¬CH3 2: ¬CH3 + Cl2 > CH3Cl + Cl¬ A radical is formed each time=Chain reaction
Ways to measure rate of change
Measure change in mass, volume, concentration or acidity. Easiest is with gas, see rate in time with syringe.
Unsaturated
Molecules that contain one or more double (or triple) bonds.
Induced dipole-dipole interactions
Movement of electrons= spontaneous dipoles formed= induce dipole of neighbouring molecules=induces weak force of temporary attraction between molecules. MORE electrons=MORE bonds=MORE energy to break.
Physical properties of alcohols
Mpt&bpt: High have induced dipole-dipole interactions and H bonds between Oxygen lone pair and hydrogen . Miscibility: Small alcohols= miscible, some H bonds form with H2O. However as Mr INCREASES=MISCIBILITY DECREASES. (big non-polar chain)
Compromise of conditions- The Haber process
N2 can't be used directly from atmosphere, so Haber process fixes it to NH3. Exothermic reaction so increase temp shifts to LEFT, increase pressure shifts RIGHT, reducing number of molecules (4:2). Lowest temp=slowest reaction and highest pressure=increase costs compromise: 427°C and 200 atm, finely divided iron or porous metal oxide promoter catalysts. Cooled NH3 goes liquid but not reactants so system tries to minimise loss of NH3 and N2+H2 react more. Unreacted N2 and H2 is recycled.
Rules of Oxidation numbers
Natural elements=0 Oxi no total 0 Oxi no of ion totals ionic charge.
Ground state
Natural state of existence with electrons in lowest energy position
What are anions?
Negative ions
Physical properties of group 17
Non-metals, poor conductors. Number of induced dipole-dipole interactions increases down group so increasing mpt&bpt. Flourine best oxidising agent and most electronegative.
Nucleophilic substitution
Nucleophile approaches carbon and backside attacks it and forms Intermediate, where the carbon-halogen bond is SLIGHTLY BROKEN and the carbon-nucleophile bond is SLIGHTLY FORMED. The carbon-halogen bond breaks forming product and HALIDE ION.
Valency
Number of electrons involved in characteristic properties of element (reactions)
Chlorine uses
Reacts reversely with H2O and resultant mixture kills bacteria. Disproportionation. Chlorine acid formed breaks microorganisms by oxidising molecules for cell structure. However chlorination may have by-products of chlorine reacting with organic matter in H2O=Bladder/colon cancer, but it's slightly controversial as links aren't established. Advantages of Cl overpower small health risks.
Bromination
Reagent: Bromine water Conditions: mix at RTP Observation: Decolourisation of bromine water. This is the test for a double bond, where it forms a dibromo product.
Hydrogenation of ethene
Reagent: Hydrogen Conditions: Nickel catalyst 150 degrees Observation: No visible change Hydrogenation of polyunsaturated compounds derived from plant oils is used in the production of margarine.
Reaction with Hydrogen Bromide
Reagent: Hydrogen Bromide Conditions: Mix at RTP Observations: No visible change
Hydration
Reagent: Water (Steam) Conditions: H3PO4 catalyst 300 degrees 6MPa Observations: No visible change Addition of water to form a new organic compound. UNSYMMETRICAL ALKENES produce TWO ISOMERS (e.g. propene).
Orbital
Region around atom nucleus which can hold maximum of 2 electrons
Equilibrium constant
Relating concentrations of reactants and products.Reaction: aA+bB~cC+dD has Kc: [C]^c*[D]^d/[A]^a*[B]^b. Value in brackets is concentration. If Kc>1 then MORE PRODUCTS= equilibrium is MORE RIGHT. If Kc <1 then MORE REACTANTS= equilibrium is MORE LEFT.
Define periodicity
Repeating patterns in either physical/chemical properties across different periods.
Economic importance of catalysts
Resources spent developing new cost-effective and efficient catalysts. Allow reactions to operate at lower temps, save energy and reduce demand on fossil fuels, reduces CO2 emissions and reduces pollution due to combustion.
Reliability of thermochemical experiments
Results are never reliable as Lack of precision of equipment (i.e. thermometer) Heat loss to surroundings Reactions are quite slow
Hydrolysis of haloalkanes
SLOW process results in halogen group being replaced by OH- to form an alcohol. requires ALKALI CATALYST. Primary haloalkane under REFLUX+ aqueous alkali> primary alcohol. Reagent: Na/K (OH) (catalyst) Conditions: Solvent MUST BE WATER, under REFLUX.
What are the main ionic compounds to know?
SO4(2-), NO3(-),NH4 (+), CO3 (2-), OH (-), Zn (+), Ag (+)
Disproportionation
Same element is simultaneously oxidised and reduced.
Homogenous catalysts
Same state/phase as the reactants, if reactants were gas= catalyst is gas. Mainly used in Esterification (H2SO4 aq), or oxidising of iodide ions (Fe3+ aq), as reactions are too slow. Ozone breakdown by Chlorine radicals is homogenous catalysis.
Oxidation of secondary alcohols
Secondary alcohol + [O] = KETONE + water. This is done under REFLUX
Displayed formula
Shows relative positions of atoms and number of bonds between them, can sometimes have bond angles around carbon atoms.
Skeletal formula
Simplified structure not writing carbons or hydrogen's but writing in other formula's.
Simple molecular lattices
Small molecules forming larger structures held by weak IMFs, which are easily broken. Molecules within are held by strong covalent bonds, which don't break leading to sublimation(Iodine). Ice=each water molecule held in position by all IMFs.
Le Chatelier's principle
States that if a closed system at equilibrium is subject to a change, the system will move to minimise the effect of that change.
Covalent bond
Strong electrostatic attraction between shaired pair of electrons and nuclei bonded. Between 2 non metals
Hydrogen bonds
Strongest electrostatic attractions between polar molecules with H and O, F & N or lone pairs
Temp effect on Kc
Sulfur dioxide reaction= as temp increases more reactants are made so MORE REACTANTS= SMALLER Kc. So as temp rises Kc DECREASES.
Endothermic reaction
Takes in heat from surroundings has enthalpy change that's positive (photosynthesis) (cold packs) Bond making requires this reaction.
Factors that affect rate of reaction
Temperature, Catalyst, Surface Area and Concentration/Pressure. Also the collision between particles has to exceed the activation energy for that reaction. Also the colliding particles must ORIENTATED CORRECTLY.
Markownikoff's rule
The Hydrogen of the reagent will attach to the most hydrogenated of the carbons in the double bond, which would form the most stable carbonium ion.
1 mole
The amount of substance that contains as many elementary particles as there are in 12 of carbon 12.
Why is the initial rate the most important rate to measure?
The concentrations and amounts of the reactant are exactly known so rate can be obtained from gradient of when time=0.
Bonding in alkenes
The double bond- single covalent bond of 2 shared pair of electrons, with electron density concentrated between nuclei. (sigma bond). A pi bond is sideways overlap of two p-orbitals on adjacent carbon atoms providing one electron. Prevents rotation and movement around the double bond. The C-H bond is about 120 (trigonal planar). If there's other alkyl groups attached have bond angles of 109.5=tetrahedral.
1st Ionisation energy
The energy change when 1 mole of electrons is removed from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ions
Structural formula
The least amount of detail or structures. E.g. C4H10 can be butane or methylpropane. Structural formula of butane CH3CH2CH2CH3. Structural formula of methylpropane CH3CH (CH3)CH3 OR (CH3)3CH.
Molar mass
The mass of one mole of a substance. (g mol-1)
Activation energy
The minimum energy needed for a reaction to take place.
Molecular mass
The number and different type of atoms of each element in a molecule.
Electrophilic Addition
The reaction is initiated by presence of a dipole on the molecule reacting with the alkene. It can be Induced by double bond (Cl2/Br2), or be Permanent (HBr). Representing this involves Curly arrows, relevant dipoles and lone pairs.
Inductive Effect
The release of electrons across a sigma bond to stabilise a cation.
Empirical formula
The simplest whole number ratio.
Free radical substitution
The substitution by chlorine or bromine to form a halogenoalkane
Relative formula mass
The weighted mean mass of a formula unit compared to the mass of 1/12 of the mass of carbon 12.
Relative molecular mass
The weighted mean mass of a molecule compared to 1/12 of the mass of carbon 12.
Relative atomic mass
The weighted mean mass of an atom of an element compared to 1/12 of the mass of carbon 12.
Alicyclic compounds
They are compounds that have a carbon ring unsaturated or not but does not have aromatic character.
Aromatic compounds
They are compounds that have delocalized pi clouds instead of discrete single and double bonds and so the bonds can move through out the structure. (Contain a benzene ring)
Structural isomers
They are compounds that have the same molecular formula but different structural formulae.
Chemical properties of alkanes
They are very unreactive as the C-H bond has low polarity and the bonds are relatively strong.
Positional isomerism
They differ with the position of the functional group, like 1-bromobutane and 2-bromobutane.
Functional group isomerism
They have different functional groups, this can be easily noticed with aldehydes and ketones: Propanal and propanone.
Stereoisomers
They have the same molecular formula and structural formula but different three dimensional arrangement.
Cahn, Ingold and Prelog rules (CIP)
They help name the isomers as E/Z. Consider atomic number to determine isomer shape. 1) HIGHEST Ar> DIAGONALLY OPPOSITE= E-ISOMER. 2) HIGHEST Ar> ARE NOT diagonally opposite= Z-ISOMER. 3) Same Ar then ADJACENT ATOMS considered. Alkyl groups follow CH3CH2CH2(43)>CH3CH2(29)>CH3(15)
Combustion of alkanes
They react with excess oxygen to form carbon dioxide and water. In a limited supply of oxygen they can form Carbon monoxide and water, or carbon and water.
Effect of temp on equilibrium position
This effect can only be predicted if enthalpy change is known. Sulfur Dioxide reaction is exothermic, if temp increased reaction will lower temp, by shifting left (endothermic reaction) so reactants are formed more.
Boltzmann distribution graph
This graph: Goes through origin=no particles had zero energy. There's no max energy as curve doesn't meet horizontal axis. Area under graph=Total number of particles.
Nitrogen monoxide
Thunderstorms produce NO. Produced by combustion in internal combustion engines, mainly exhaust of aircraft. Most oxidised+combine with moisture= acid rain (HNO3), some reaches stratosphere and attacks O3. NO INITIATION STEP as NO POSSESSES UNPAIRED ELECTRON. Propagation: ¬NO+O3>¬NO2+O2 and ¬NO2+O>¬NO+O2 The net reaction is O3+O>2O2 and the first NO is regenerated so is a catalyst.
Initiation
Ultraviolet radiation energy to break Cl-Cl bond HOMOLYTICALLY forming radicals. Cl-Cl (uv light)> 2Cl¬
Ammonium ion test
Warm NH4+ with NaOH producing NH3 gas which turns MOIST RED LITMUS- BLUE
Elimination/ Dehydration
When alcohols are reacted with CONCENTRATED H2SO4/ HOT PUMICE (Al2O3), the alcohol can be dehydrated to form an alkene. Two products can be formed if there are more than 3 carbons and both E and Z isomers are formed.
E-isomer
When they are DIAGONALLY OPPOSITE each other.
Z-isomer
When they are on the SAME side
Relationship between moles of gas and gas volume
n (mol)=V(cm3/dm3)/molar volume (cm3/dm3)
Relationship between concentration, moles and volume
n (moles)=Conc(mol dm-3)×Vol(dm-3)
Electronegativity
Ability of atom to attract electrons to itself in a covalent bond.
The reaction of Asymmetric alkenes with HBr and H2O
Asymmetric alkenes react with HBr and H2O but form two products unequally. Hydrogen mainly goes to MOST HYDROGENATED carbon. When H attaches it forms Carbocation= UNSTABLE, ADJACENT alkyl groups stabilise with INDUCTIVE EFFECT. Hydrogen bonds to make more stable carbocation, tertiary is more stable than primary with 3 alkyl groups inducing.
Trends across a period
Atomic radius DECREASES- nuclear charge increases (pulls electrons in) & shielding stays the same
Reagents
Chemicals involved in reactions
Formation of bleach
Cl+NaOH》NaCl+NaClO+H2O another Disproportionation reaction.
Waste polymer alternatives
Development of bio-degradable polymers, made from renewable raw materials like starch but more expensive. Require certain conditions to degrade (oxygen& moisture) and sorting of polymers. Need active functional group to be attacked by bacteria, and be sustainable. Development means less usage of finite materials and reduce disposing plastics.
Enthalpy change
Difference between the enthalpy of products and the enthalpy of reactants.
Ion
Electrically charged particle formed by the loss/gain of electrons
Effect of concentration/ pressure
Increasing conc increase chances of collisions between particles, the more collisions the quicker the rate. Increasing pressure for gases then rate increases as there is more chance for collisions.
Effect of pressure on equilibrium
Increasing pressure on 2SO2+O2》2SO3 equilibrium shifts RIGHT. 3 molecules of reactant, but 2 of product, equilibrium shift to reduce total no. of molecules. Pressure increase on this 2HI》H2+I2 wouldn't shift equilibrium as there's equal number of gaseous molecules each side.
Effect of temperature
Increasing temp= increases energy given to particles and so more particles exceed the Ea, so more can react increasing the rate compared to lower temps. Distribution curve of higher temp is FLATTER and SHIFT RIGHT, to increase proportion of particles with greater energy.
What does mass spectroscopy provide?
Information about masses of particles inside machine and how often it's detected.
Three steps to Radical substitution
Initiation- Starts the reaction by forming a radical Propagation- Forming one product and a new radical. Termination- Ends reaction- removing radicals forming molecules.
Termination
Involves two radicals meeting together to form covalent bond 1: ¬CH3 + ¬CH3 > C2H6 2: ¬CH3 + Cl¬ > CH3Cl 3: Cl¬ + Cl¬ > Cl2
Cis-trans isomerism
Is a special case of E/Z when the groups attached to the double bonded carbons are THE SAME.
Effect of catalyst on equilibrium
It DOESN'T alter amount of product. It speeds up the forward AND reverse reactions. So it has NO EFFECT on equilibrium. It can reduce time to reach equilibrium and same amount of product is produced quickly.
Chemical properties of group 2
Lose 2 electrons=2+ cations. Reducing agents Ba best to lose electrons. Burn brightly in oxygen=group 2 oxides. React with H2O= produce group 2 hydroxide+ hydrogen. Except Mg reacts H2O slowly so use steam. React with Cl= white chlorides. React with dilute acid=Salt + hydrogen.
Homolysis/ Homolytic Fission
Occurs when a covalent bond is broken so that the atoms joined by the covalent each take one of the shared electrons.
Oxidation of primary alcohols
Oxidation agent: Acidified Potassium dichromate (VI) orange-green alcohol oxidised. Primary OH + [O] = ALDEHYDE + water. DISTILLATION: aldehyde removed on production. Aldehyde has lower bpt and readily vaporises and collected as liquid. Primary OH +2[O] = CARBOXYLIC ACID + water. REFLUX: continuous evaporation and condensation. Aldehyde reaches VERTICAL condenser, falls back into [O] and is FURTHER OXIDISED.
Why can't tertiary alcohols be oxidised?
Oxidation only occurs when the Carbon bonded to the OH is ALSO BONDED TO AT LEAST 1 HYDROGEN, tertiary alcohols don't have this trait and so cannot be oxidised.
Relationship between Temp, pressure and volume
P1V1/T1 = P2V2/T2
Ideal gas equation
PV=nRT
Weak acid
Partially disassociates in water. (CH3COOH)
Molecular ion peak
Peak corresponding to relative molecular mass of the compound (parent peak)
Waste polymers
Polymers difficult to dispose, have strong covalent bonds and non-polar= resistant to chemical attack and bacteria. BURIED in LAND-FILLS is useless. DIFFICULT to RECYCLE- SO MANY plastics to separate and sort. Cracking larger polymers, melting them and remoulding them makes monomers (organic-feedstock). Combusted- hydrocarbons good resources for fuel, however some plastics (PVC) produces POISONOUS GASES (HCl), can be neutralised by gas scrubbers.
What are cations?
Positive ions
Base
Proton acceptor.
Acid
Proton donor
Dynamic Equilibrium
Rate of the forward reaction is equal to the rate of the reverse reaction. Concentrations remain constant, and reactants and products react continuously. Only achieved in a CLOSED SYSTEM.
Relative Isotopic mass
The mass of an isotope of an element compared to 1/12 of the mass of carbon 12
Equation for enthalpy changes
q=mc♢T
Trigonal Planar
3=BP 0=LP A=120° 3 electron pairs
Trigonal Bipyramidal
5=BP 0=LP A=120° & 90° 5 electron pairs
Avogadro's constant (Number of particles per mole)
6.02e^23
Octehedral
6=BP 0=LP A=90° 6 electron pairs
Detection
A calibrated detector records degree of deflection and interprets this into mass
Anhydrous
A compound with no waters of crystallisation.
Hydrated
A compound with water in its structure.
Ionisation
A gaseous sample is bombarded with high energy electrons to create 1+ ions
Strong acids
Completely disassociates into ions in water. (HCl, HNO3, H2SO4, H3PO4)
What is shown on mass spectrum?
Different isotopes relative abundance and molecular peak is furthest to right
Electron configuration points to consider
S-orbital have less energy than d orbitals of principle quantum numbers. Always fill orbital with 1 electron first before pairing. Electrons have different directions of spin.
Alkali
SOLUBLE BASE (NaOH, KOH, NH3)
Water of crystallisation
Salts with water present in crystal form
Describe an S-orbital
Simplest of all, is spherical. The quantum number dictates how far away from the nucleus it is.
What's responsible for trends of 1st IE in first 20 elements?
Sub-shells
Conditions in ideal gas equation
T=°K V=dm3=P=kPa V=cm3=P=Pa
Why are there sometimes line after the parent peak?
They are a result of carbon 13 isotope and isn't considered when identifying a compound
Acceleration
They are accelerated through magnetic/electric field
Dative (coordinate) bond
Two electrons are provided from 1 atom. Electrostatic attraction between electron pair and nuclei if bonded atoms makes the covalent bond.
Why do you fill each orbital with one electron before adding in pairs?
Two electrons in same orbital experience some repulsion making pairing less favourable
Solubility of ions
Water is polar and so binds to ions (hydration) and is able to overcome ionic bond to disassociate the ionic compound.
Permanent dipole-dipole interactions
Weak electrostatic attraction between NEIGHBOURING POLAR molecules.
