all general memory Flashcards
What happens at the cathode
Reduction of cations (positive ions)
What happens at the anode
Oxidation of anions (negative ions)
What is an electrolyte
A substance which can dissociate into ions (in water or alone)
What is an electrode
A solid electric conductor which carries current into the electrolyte
What is a strong electrolyte
Something which completely dissociates (ionisations) into ions - for example NaCl
What is a weak electrolyte
Partial ionisation/dissociation into ions, in equilibrium - water and most organic acids and bases are weak electrolytes
Define electrolysis
The decomposition of a substance via passage of a DIRECT current which would otherwise not be spontaneous
Why direct current?
Keep the deposits/split of materials at each cell consistent so one thing is all deposited in one place. If polarity is continuously changing the ions will be continuously switching which cell they’re attracted to and move in opposite directions. Uneven deposition of particles.
Products of electrolysis: molten binary compound
only 2 ions: positive goes to cathode and is reduced, negative goes to anode and is oxidised
In a half equation representing reduction which side do the electrons appear
The side of the reactants (reductions/reactant)
In a half equation representing oxidation which side do the electrons appear
The side of the products (oxidation/products)
At the cathode what do different deposits look like
Pretty much every metal is a silvery grey solid except copper (Cu) which is a brown solid and gold (Au) which is… gold
At the anion what do the halogens get deposited as
Chlorine = greenish yellow gas, Bromine = brown gas, Iodine = purple gas
Test for halogen gases?
Damp blue litmus paper turns RED
At the anion what does oxygen appear as, how do we check it’s oxygen?
colourless gas bubble - relights a glowing wooden splint
Products at the cathode: aqueous solutions
Hydrogen (H2) gas in all cases EXCEPT when there are Au+, Ag+ or Cu2+ ions, in which case you will get gold, silver or copper
Products at the anion: aqueous solutions
If there’s halide ions present you’ll get the halogen gas, if not O2 (oxygen gas) from water
Half equation for the reduction of H+ at the cathode (acidic conditions)
2H(+)(aq) + 2e- -> H2(g)
Half equation for the reduction of H+ at the cathode (alkaline conditions)
2H20 + 2e- -> 2OH- + H2
Half equation for the oxidation of OH- at the anode (acidic conditions)
2H2O -> 4e- + 4(H+) + 2O2
Half equation for the oxidation of OH- at the anode (alkaline conditions)
4OH- -> 4e- + 2H2O + O2
define electroplating
surface of one metal (CATHODE) is coated with another (ANODE)
What should the electrolyte be for electroplating
A solution which contains the metal ion of the anode (the metal being used to coat the cathode metal)
In electroplating which electrode metal is more reactive
The metal being coated is more reactive and the one thats coating the cathode is less reactive
Do electrons flow into or out of the cathode
Electrons flow into the cathode
Do electrons flow into or out of the anode
Electrons flow out of the anode
Name some amphoteric oxides/hydroxides
ZnO, Al2O3, Al(OH)3, PbO, GeO, SnO, PbO2, GeO2, SnO2
Oxides of non-metals tend to react with water to form what kind of solutions? Name some
Oxides of non-metals tend to react with water to produce acidic solutions (CO2, SiO2, SO2, SO3) Acidic oxides are known as acid anhydrides, reacting with bases to form salts (for example sulfur trioxide is sulphuric anhydride and reacts with NaOH to form NaSO4 and water)
Describe the trend in pH of the group 4 oxides
From acidic at the top to amphoteric at the bottom
What are some neutral oxides
CO, NO, N2O
Oxides and hydroxides of metals tend to react with water to form what kind of solutions? Name some
They form alkaline solutions. Oxides and hydroxides of G1 and G2 metals form basic oxides. NaOH, Na2O, K2O, BaO, MgO. Basic oxides are known as ba
What is the reaction between water and a G1/G2 oxide
Water and G1/G2 oxide react to form a G1/G2 hydroxide
general formula of alkanes
CnH2n+2
name the alkanes from C1 to C10 (the specification says C1 to C6)
methane, ethane, propane, butane, penance, hexane, heptane, octane, nonane, decane
number of isomers of the alkanes
butane = 2 isomers, propane = 3 isomers, hexane = 5 isomers
name the alkenes from C2 to C6 including the position of the bond
ethene, propene, but-1-ene and but-2-ene, pent-1-ene pent-2-ene, hex-1-ene hex-2-ene and hex-3-ene
general formula of alkenes
CnH2n
test for unsaturation with bromine water
in the presence of alkenes bromine water will decolourises and turns from orange to colourless. Makes dibromoalkane (electrophilic addition across the double bond) where bromine water is an oxidising agent. You’l probably get a mix of this and -Br, -OH added across the double bond.
Describe the reaction of alkenes with hydrogen
An addition reaction/hydrogenation reaction where the hydrogens add across the double bond. Reduction of the alkene/saturates the organic compound. No regioselectivity as the 2 parts are the same. An example of a heterogenous catalysis reaction. Makes margarine from vegetable oil as this raises the melting point. Fats have (hydrogenated fats) are solids are room temperature whereas oils are liquid, fats have higher melting points than oils. Nickel catalyst/150 degrees.
Describe the reactions of alkenes with halogens
Electrophilic additions reaction. Induced dipole when the halogen approaches the double bond as it’s a region of high electron density/negative charge. Creates a dihaloenoalkane. HETEROLYTIC BOND FISSION - one atom gets bond electrons and ions are formed. Chlorine reacts faster than bromine. Bromine will decolourise.
Describe the reactions of alkenes with hydrogen halides
Electrophilic addition reactions. hydrogen has a positive dipole and the halogen has a negative dipole. The hydrogen adds first and then the halide adds to the carbocation formed. Major and minor products are formed. The major product is the one formed via the more stable carbocation (tertiary>secondary>primary). These are Markovnikov additions and an example of regioselectivity. Only relevant to unsymmetrical alkenes. Positive inductive effect from the methyl groups creates a less positive carbocations so more a formed. It’s about stability not about consequent reactivity. In terms of rate of reactions. HI reacts the fastest and HF the slowest because the H-I bond is the longest and weakest. Tertiary reacts faster than secondary etc.
Describe the reactions of alkenes with steam
addition reactions/ hydration reaction to produce an alcohol. 300 degrees, 60/70 atm and a phosphoric acid catalyst.
(NOT SPEC) Oxygen and alkenes react slowly to produce what
organic peroxides
(NOT SPEC) what is the reaction between hydrogen halides and alkenes in the presence of organic peroxides
a chain free radical reaction happens. The R-O-O-R bond breaks producing R-O’ free radicals. These free radicals react with the H in the HBr producing an alcohol and a bromine free radical. Bromine free radical uses one of the electrons in the pi bond to bond to one of the carbon atoms and leaves the other carbon atom with a free radical. This free radical reacts with another Hbr to produce a bromoalkane leaving behind another Br. free radical. The products can be predicted by the anti-markovnikov rule as the halogen is the one being added first not the hydrogen. This is a faster reaction than electrophilic addition.
define molecular formula
it’s the number of atoms actually in the molecule. For example C6H12O2 (the empirical formula would be C3H6O)
Define empirical formula
Simplest whole number ratio of atoms in a compound
FULL structural formula
this is DISPLAYED STRUCTURE. I don’t know why they like to confuse things. It is the drawn out molecule with lines connecting each atom and the atoms identities all written out clearly.
Condensed structural formula
linear form of displayed formula without lines connecting, using brackets to show branching.
Carbon chain length relationship with boiling point
As carbon chain length increases so does boiling point because there are more London forces (more induced dipoles). It is proportional to surface area as well so branched chains will have lower boiling and melting points than comparable straight chain as there’s less SA exposed
Carbon chain length and viscosity
Longer chain more viscous. Molecules held closer together due to stronger London forces. Also get tangled up like strings so it’s more difficult to flow past each other. Viscosity decreases as temperature increases.
Flammability and carbon chain length relationship
Less flammable as chain length increases. More energy is stored per molecular but they require more energy to be in the gas phase to mix with oxygen and combust.
What is the main source of hydrocarbons
The main source of hydrocarbons is CRUDE OIL and is separated by FRACTIONAL DISTILLATION. Long chain alkanes are used in cracking to form shorter chain alkanes and alkenes. It is impossible to form 2 alkanes from 1 alkane you must form some unsaturated products as well
What is structural isomerism
Compounds which have the same molecular formula but different structural formula
What are the kinds of structural isomerism
Positional (functional group in a different position), Chain (the carbon skeleton is arranged differently) and functional group isomerism (the functional group is different for example ketones and aldehydes, alkenes and cycloalkanes, alcohols and ethers, carboxylic acids and esters etc.
Define complete combustion
Something burns in oxygen producing ONLY CO2 and H2O. Balance Carbons, then hydrogens and then oxygens
Define incomplete combustion
Can lead to formation of CO and C, the balancing number for water is the same but not for CO2
Define homologous series
Can be described with a general formula with similar chemical properties and predictable physical properties. Same functional group but different carbon chain length.
Define functional group
The part of an organic compound that is involved with reacting. The react in the same way no matter the carbon chain attached.
What type of reaction is combustion
Combustion is a redox reaction where the O2 is reduced (from ox num 0 is O2 to ox num -2 in water and carbon dioxide) and Carbon is oxidised as is Hydrogen. High temp exothermic with organic fuel as the O2 bond broken is much weaker than the bonds formed
Priority for carbon number least to most
halogens, alkyl groups, alkenes, alcohols, ketones/aldehydes, carboxylic acids (HAAAAKC)
Explain how you name organic compounds (prefix/sufic, position of carbon chain etc.)
When you add an ending, remove the ‘e’ from alkane or alkene e.g. methanol, propenol. Don’t remove this e if the suffix starts with a consonant or if di,tri,tetra,penta follow it. e.g. butane-1,2-diol. Number and words separated by a dash. Numbers and numbers separated by a comma. If there is more than one prefixed functional group. List them in alphabetical order.
define addition polymerisation and explain the process (peroxides)
Small monomers join to make one large polymer. Alkenes become long chain saturated polymers. One way this can happen is with organic peroxides as initiators in stepwise free radical chain reactions. The O-O bond breaks easily, lots of lone pairs so electrons repel. They break homiletically to produce free radicals. This is the initiation step. The propagation step is where the free radical bonds with one of electrons in the pi bond leaving the other carbon in the double bond with a free radical. This can go on to react with another alkene etc. the termination step is when 2 compounds with free radicals react together.
Naming addition polymer products?
But-1-ene becomes poly(but-1-ene). Unsaturated monomers are called monomers. Long chain saturated molecules are called polymers.
Define repeat unit
Smallest part of the polymer which when repeated can generate the polymer
Define condensation polymerisation
Condensation is a type of addition reaction which releases a small molecule like water or HCL. Unlike addition polymers these can undergo hydrolysis in acidic or alkaline conditions to break them up again so are biodegradable
Polyesters
Formed from a hydroxycarboxylic acid or one diol and one dicarboxylic acid. Linked by ester bonds and in each case produce (2n-1)H2O molecules where n is the number of diols or number of dicarboxylic acids. If given number of hydroxycarboxylic acids it’s n-1.
Polyamides
Formed from an diamine an dicarboxylic acids or from a compound with a carboxylic acid functional group on one end and an AMINE functional group on the other end which is an amino acid. The amide like is C=O bonded to an N-H. Amide/peptide link.
Explain what biodegradable and non biodegradable mean when applied to polymers
Addition reactions are pure addition reactions whereas condensation polymer formation involves both addition and elimination (condensation) reactions. In addition all carbon bonds are single. In polyesters the bonds are ester linkages and in polyamides amide linkages. Addition polymers require high temperature and pressure whereas condensation polymers can usually happen via hydrolysis.
General formula of alchohols
CnH2n+1OH (names are methanol, ethanol, propanol, butanol, pentanol and hexanol
Describe the reaction of alcohols with sodium metal
Sodium + alcohol -> sodium alkoxide + hydrogen. For example 2Na(s) + 2CH3OH(l) -> 2CH3ONa(l) -> H2(g). Sodium alkoxide is a colourless salt solution which when evaporated will leave behind a white solid. The gas evolved can be tested to be hydrogen with a squeaky pop. Can be a test for alcohols if bubbles of hydrogen gas are produced.
General formula of carboxylic acid
CnH2n+1COOH (methanoic acid, ethanoic acid, propanoic acid, butanoic acid, pentanoic acid and hexanoic acid. Weak acid
Reaction of carboxylic acid and water
In water a hydrogen ion is transferred from the COOH group to a water molecule CH3COOH + H2O -> CH3COO- + H3O+
Reaction of carboxylic acid and metal
Produces HYDROGEN GAS H2 and an ‘anoate/metal ion’ salt solution
Carboxylic acid + hydroxide reaction
Produces metal anoate salt solution and WATER this is an exothermic neutralisation reaction. For example NaOH + CH3COOH -> CH3COONa + H2O a colourless solution containing sodium ethanoate.
Carboxylic acid + Carbonates/hydrogencarbonate
Same acid base neutralisation you would expect. Producing CO2 and H2O and an anoate salt. With reactions with a carbonate. The carbonate ion has a 2- charge whereas the anoate only has a 1- so in the balanced equation there should always be 2:1 ration of carboxylic acids to carbonate. In terms of observation: you will see immediate fizzing and a colourless solution being formed
Carboxylic acid + Ammonia
Produces an ammonium -anoate solution (ONE PRODUCT)
carboxylic acid and amines
Produces the same kind of thing as with carboxylic acid and ammonia, remember that amides are just ammonia but with the hydrogen groups subbed in with alkyl groups. CH3COOH + NH2CH3 -> CH3COONH3CH3 (ethanoic acid + methylamine -> methyl ammonium ethanoate)
Carboxylic acid and alcohols
Carboxylic acids + alcohol -> ESTER + water with an acid catalyst H2SO4. It is a reversible reaction to increase yield use excess alcohol or acid, more concentrated H2SO4 than required for catalytic effect as it can react with the water formed to encourage the forward reaction. Distil the ester or water as it’s being formed to encourage completion. Small ester have a lower boiling point as no hydrogen bonding.
explain what the pH formed by different salt solutions is determined by
the pH of a salt solution formed from the salt of a weak acid and a weak base is neutral. From a weak acid and strong base is basic and from a strong acid and weak base is acidic. From a weak acid and weak base is neutral but may depend on relative weakness/basicity of each. Like which Ka or Kb is higher.
describe skeletal formula
lines show bonds between carbon atoms but you don’t actually write the carbon atoms in. Lines show bonds o functional groups. Every vertices that doesn’t have a functional group on it is a carbon. No hydrogens unless in a functional group. Double line is pi bond
define stereoisomerism
same molecular formula but the atoms are arranged differently in space
types of steroisomerism
there is geometric/EZ isomerism which is exhibited around a double carbon bond where the species on one side of the bond are different. Alkenes exhibit this around their planar 120 degrees double bond. Restricted rotation around the bond due to p orbitals on each carbon overlapping above AND below the sigma bond. High electron density means more reactive than alkanes as its vulnerable to electrophilic attack.
General formula of cycloalkanes
CnH2n (same as alkenes) the are SATURATED cyclic hydrocarbons) Names: cyclopropane is the simplest, cyclobutan, cyclopentane, cyclohexane etc.
Define an addition reaction
two molecules join together to form a larger molecule. They are characteristic of double bonds. All unsaturated compounds can be saturated by reactions with hydrogen in the presence of a nickel catalyst in a hydrogenation reaction (can all be reduced). With platinum/palladium at room temp or with nickel at 150 degrees.
Electrophilic addition of sulphuric acid.
Also nucleophilic addition of aldehydes/carbonyl compounds which forms hydroxynitriles using HCN or KCN
define an elimination reaction
an elimination reaction splits of a small molecule like H2O and leaves behind a double bond. For example elimination reaction of haloalkanes leaves behind an alkene (using ethanolic sodium hydroxide) OH ions act as a base.
Dehydration of alcohol to give an alkene and steam (essentially cracking) using phosphoric acid, sulphuric acid is a strong oxidising agent and may oxidise some of the alcohol to aldehyde or ketone. Happens at 170degrees
define a substitution reaction
Replacing one group of atoms by another group of atoms. Substitution reactions are characteristic of haloalkanes as their polar part makes the partially positive carbon liable to nucleophilic attack - NaOH = alcohol, HCN = nitrile, NH3 = amine. SN2 is primary and secondary haloalkanes with a transition step that is the peak of the reaction profile, SN1 is tertiary haloalkanes. and has a stable intermediate which is the middle of the camel bump.
Free radical substitution of alkanes in UV
Electrophilic substitution of benzene (the mechanism you’re most familiar with - unstable intermediate with an open e- system, H gives electrons to the delocalised system in a rapid second step. Bromination and nitration
Explain oxidation reactions of organic compounds
alcohols to ketones/aldehydes. Aldehydes to carboxylic acids. Alkanes to alkenes. Alkenes to alcohols. Carboxylic acid to carbon dioxide (combustion is oxidation of organic compounds). Functional group level of the carbon increases in oxidation (functional group level is how many bonds does a carbon make with more electronegative atoms like oxygen.
define hydrolysis
Splitting apart with water (often catalysed its acids or alkalis), are usually substitution reactions in which the chemical attack is by nucleophiles such as water molecules or H2O molecules. For example the reaction of haloalkanes with water to form alcohols and hydrogen halides
describe the free radical substitution of alkanes
- Initiation: The halogen splits into 2 halogen free radicals this is homiletic bond fissions as each atom gets one electron each. UV light requires, photodissociation
- Propagation: The halogen free radical reacts with the alkane taking a hydrogen away and producing a hydrogen halide and leaving behind an unpaired electron on one carbon atom. Alkane free radical.
This free radical reacts with a non split halogen molecule , taking a chlorine to bond with it’s unpaired electron and leaving behind a chlorine free radical. It’s a catalyst as it’s reformed at the end. - Termination: chlorine free radical and alkane free radical may react together to form the haloalkane.
The propagation section is the ‘chain’ part of the reaction and can continue. Further substitutions of the haloalkane can produce dihaloalkanes etc. Make haloalkane in excess so the products will mainly be single substituted.
What is homolytic fission and heterolytic fission
Homolytic means the bond will break evenly and each atom gets one electron forming free radicals. heterolytic fission is formation of ions when one electron gets both electrons in the bond. Often happens in polar solvents or when the bond already has a dipole - creates ionic intermediates.
What reactions do haloalkanes undergo
NUCLEOPHILIC SUBSTITUTION Sn2 and Sn1. The halogen is the leaving group and the nucleophile must have a lone pair. If the nucleophile is negatively charged when it bonds to the carbon it will be neutral however if it’s already neutral (NH30 then when it bonds to the carbon it will have a positive charge). The lone pair means the bond formed with the carbon is a coordinate or dative bond and the more electronegative leaving group will take both electrons from the bond - heterolytic bond fission
Describe SN2 substitution including any changes in optical isomerism (not spec)
SN2 goes through a TRANSITION step which is unstable. The nucleophile approaches from the back (opposite side of the leaving group) so flips rotation of light. Product and reactant rotate plane polarised light in opposite directions
Describe SN2 substitution including any changes in optical isomerism (not spec)
SN1 goes through a stable intermediate - the nucleophile can add onto this carbon from above or below the trigonal planar carbocation intermediate so produces a mixture which is not optically active unlike the reactants which are. The first step which requires the C-X bond breaking is slow so this reaction type is governed by how fast the C-X bond ionises.
Nucleophilic substitution of haloalkanes with NaOH, HCN and NH3 - conditions and products
Products: alcohol, nitrile, ammonium salt or amine if treated with a strong base. Conditions: aqueous warm and reflux, ethanolic and reflux, ethanolic sealed and warm. For reaction with ammonia, if you treat it with a strong base you release the weaker base (amine) from the salt or else you can use excess ammonia.
Further substitution reactions possible as the primary amine is an even more reactive nucleophile than ammonia because of the electron realising (positive inductive) effect of the alkyl group.
What type of reaction is haloalkane to alkene? What are the conditions
It’s an elimination reaction with NaOH as a base in ethanolic conditions. Hot and reflux. Creates water and a halide ion as well as the alkene. Multiple products possible.
What type of reaction is alcohol to alkene? What are the conditions
An elimination reaction that can be described as dehydration with a phosphoric acid catalyst hot, concentrated and in excess. Alternatively, pass the alcohol vapour over heated aluminium oxide powder the ethanol is basically cracked to give ethene and water vapour.
(NOT SPEC) explain Zaitsev rule for elimination reactions
The more substituted alkene will be the major product. more substituted means more carbons attached to the carbon which is having it’s hydrogen removed.
Difference in the number of products produced by elimination vs. substitution
elimination results in an increase in the number of species whereas substitution doesn’t. There’s an increase in entropy for elimination reactions so the ‘-TS’ term in Gibbs free energy gets more and more negative as you increase temperature eventually G will be more negative than for a substitution reaction
Oxidation of alcohols products conditions
solution of sodium/potassium dichromate (K2Cr2O7) acidified in concentrated H2SO4 showing a colour change from orange to green
Primary alcohol to aldehydes and carboxylic acid
Secondary alcohols to ketones
Tertiary alcohols do not oxidise
For primary alcohols you get an aldehyde if you use excess alcohol and distil of the aldehyde as it’s formed (excess so that there isn’t enough oxidising agent and distillation so it doesn’t hang around long enough to be oxidised anyway). You get a carboxylic acid if done under reflux and with excess oxidising agent
Half equation for the reduction o dichromate anion
Cr2O7(2-) +14H+ +6e- -> 2Cr(3+) + 7H2O
When might you get a mix of products in electrophilic addition of alkenes
When the electrophile is not the same. The major product will be formed via the more stable carbocation which is the carbocation that has the most alkyl groups attached. Only matters If the alkene is unsymmetrical. Positive inductive effect electron releasing methyl groups creates a less positive carbon - more stabilised system is more likely to form .
How does bond energy effect reactivity
Weaker bonds react faster. For example the reactivity of the C-X carbon to halogen bond increases in reactivity down the group as the bond length increases due to the increases number of shells in the halogen. This increased distance between the halogen and the bonding pair of electrons makes it a better leaving group as its nucleus is less strongly attracted to the pair of electrons. Bond length is the most important factor in bond energy.
Hydrolysis of haloalkanes to alcohols as a test for bond strength
If you do this reaction in an ethanolic solution of silver nitrate (AgNO3). The hydrogen halide produced will react with silver nitrate in a precipitation reaction. The precipitate forming first is the C-X bond which is weakest (most reactive). Order formed: Yellow, cream white which is Iodine, bromine then chlorine. Tertiary carbocations are also more stable than secondary and primary
Explain how bond polarity effects reactivity
Having a polar bond makes things susceptible to nucleophilic attack. It makes carbon electrophilic and susceptible to attack.
Explain negative and positive inductive effect
When a more electronegative element is attached to carbon (for example, oxygen, nitrogen, fluorine) it has a negative inductive effect drawing electron density away from carbon and making it more positive. When a less electronegative element is attached (hydrogen!) it pushes electron density towards the carbon atom and makes it slightly more negative than otherwise. As a result the adjacent carbon may be more negative (this is hoe positive carbocations are stabilised, made less positive, by positive inductive effect)
The inductive effect is on the adjacent carbons.
Describe the Tollens reagent test
Diammine silver (I) ion [Ag(NH3)2]+ made from silver nitrate with a drop of NaOH to give Ag2O then redissolved in ammonia.
Ketone = NO change colourless solution Aldehyde = colourless solution to a grey precipitate of silver or a silver mirror on a test tube
test needs to be gently warmed in a water bath, aldehydes reduce the diammine silver (I) to silver and it itself is oxidised to a carboxylic acid
Ag(NH3)+ +e- -> Ag + 2NH3
RCHO + 3OH- -> RCOO- +2H2O + 2e-
Test for carboxylic acid
Reacts with metal carbonates to produce a carboxylate salt and CO2 - bubbled through lime water( Ca(OH)2) confirms this
Test for alcohol (1,2,3)
Add a few drops of acidified potassium dichromate solution. If it’s 1 or 2 it’ll turn green (orange to green upon heating). if it’s 3 it will not change and it’s definitely a tertiary alcohol.
How to confirm something is an alcohol
Make sure it’s free of water and add PCl5 a burst of steamy hydrogen chloride forms
Whats the purpose of a centrifuge
Separates components of a heterogenous mixture (blood, fat from milk) denser things move to the outside
Whats the purpose of chromatography
separates coloured soluble substances (homogenous mixture of chlorophyll from a solution of different plant pigments)
What happens to metals in a redox reaction
They’re oxidised and act as reducing agents
What happens to non-metals in redox reactions
They’re reduced and act as oxidising agents
What are the diatomic molecules
All halogens (F, Cl, Br, I), Oxygen, Nitrogen and Hydrogen
What happens to the stability of Group 2 carbonates and nitrates down the group
Stability INCREASES down the group as the cation is less polarising so distorts/weakens the covalent bond in the anion less.
Whats the equation for the thermal decomposition of Group 2 carbonates
XCO3 -> CO2 + XO
Carbon dioxide and group 2 oxide
Whats the equation for the thermal decomposition of Group 2 nitrates
produces nitrogen dioxide, oxygen and group 2 oxide.
2X(NO3)2 ->4NO2 + 2XO + O2
Describe a test for an OH group
solid PCl5 reacts with violently to produce clouds of hydrogen chloride gas
what Is the base peak in bas spectrometry and what does in represent
It’s the highest peak in a mass spectra representing the most stable fragments/most common fragment. Given an arbitrary heigh of 100 and everything else is measured relative to this.
A tertiary carbocation is more stable than 2/1 Acylium ions ( R-C+=O: R-CtriplebondO+ ) has resonance effects between 2 different structures which helps stabilise what would otherwise be an unstable ion
Describe the uses and basics of NMR
Used to measure the molecular mass of a molecule. The parent peak or molecular on peak with the largest m/z is due to the complete molecule. Molecular ion formation produces an ION and a FREE RADICAL and it’s the ION which is detected. The molecular ion can fragment further due to covalent bonds breaking.
Think about the fragmented carbon chain group as being 15+15+15 etc. with each extra carbon -1 from the multiple of 15. So methyl is 15, ethyl is 29, propyl is 43 etc
Whats the ground state of a species
The ground state is the lowest possible energy arrangement of electrons for a species. This just means that the electrons have been filled up from the lowest energy shell one by one to a higher energy one. The ground state of Ca+ is still Ca+ (NOT Ca, they are different species).
For an ideal gas, what is the only thing KE is dependant on?
TEMPERATURE: KE=3/2RT
So kinetic energy is proportional to kinetic energy (constant of proportionality it 3/2 x gas constant)
Whats the most reactive metal, what is the reactivity of a metal linked to
The reactivity of a metal is linked to its tendency to form positive ions and the ease at which it does this determines it’s reactivity. Francium is the most reactive alkali metal because it’s valence electrons are the greatest distance away from the nucleus so experiences the most shielding. For this reason group 1 metals are more reactive than their group 2 counterparts which have 2 electrons to remove and also 1 more proton attracting within the same shielding.
Which metals can be extracted via electrolysis of molten compounds
Potassium, sodium, calcium, magnesium and aluminium
the square crossing group 1 and 2 and aluminium
what does the extraction of metals always involve
REDUCTION process (a metal in a compound is an a positive oxidation state and an uncombined metal has an oxidation state of 0 so it’s a reduction from a metal in a compound to a the metal by itself)
How are Zinc, Iron and Copper extracted (not spec)
They are extracted via a reduction reaction with carbon in which CO2 is produced
C + metal oxide -> CO2 + metal
How are silver and gold extracted (not spec)
Often found uncombined
List some metal ores name and formula (not spec)
Bauxite Al2O3, Hamite Fe2O3, Pyrite Fe2S,
What happens during a metal displacement reaction and why
A more reactive metal will displace a less reactive metal from its compound. In an aqueous solution, the more reactive metal will disappear and the less reactive metal will precipitate (possibly coating the surface of the more reactive metal).
For Example:
Mg + CuSO4 -> MgSO4 + Cu
Blue CuSO4 colour fades and solution turns colourless. Brown copper coats magnesium
3 properties of transition metals on the spec
- Form coloured compounds
- able to form stable ions in a different oxidation state (up to the sum of electrons in 4s plus unpaired electrons in the 3d sub shell except for copper which likes to form a 2+ as well)
- They are good catalysts
Iron
Iron catalyst is used in the Haber process to make ammonia for fertilisers etc. It has a high density, is magnetic and corrodes easily. Alloyed with carbon to make steel (which is harder and stronger and less liable to rusting) and used for building construction.
What is an alloy
An alloy is a mixture of 2 or more elements one of which must be a metal (for example brass is mix of copper and zinc). Alloys are often harder because the irregular atom sizes means the metal layer can’t slide past one another
Aluminium
Low density, no corrosion and it’s not magnetic. Often covered with a layer of aluminium oxide . Good conductor and used in aerospace
Copper
Malleable ductile and a good conductor of heat and electricity, used for wiring. Copper and alloys are resistant to corrosion (oxide laser protects it)
silver
Most conductive, ductile and has antibacterial properties. When silver tarnishes the reaction is with oxygen in the air and hydrogen sulfide
Ag + H2S + O2 -> Ag2S + H2O
Gold
Inert, Malleable, ductile and resists corrosion staying quite shiny
Titanium
Used in alloys to add strength and make is resistant to corrosion
Gas to liquid
Condensing (releases energy, exothermic)
Vibrate less, more densely packed, decrease in energy and movement/speed
Gas to liquid
Condensing (releases energy, exothermic)
Vibrate less, more densely packed, decrease in energy and movement/speed
For condensation to happen - enthalpy of vaporisation < 0
Liquid to solid
Freezing (releases energy, exothermic)
Decrease in energy and intermolecular forces overcome kinetic energy of vibrations
For freezing to happen -enthalpy of fusion < 0
solid to liquid
Melting (requires energy, endothermic)
For fusion to take place enthalpy of fusion > 0
Liquid to gas
Evaporating or boiling (requires energy, endothermic)
When an object is heated gains energy and vibrates faster in it’s position, the structure is weakened until the particles gain enough energy to break free of the structure. To melt a solid enough energy needs to be supplied that the forced of attraction are over come. Vibration over come attractive forces.
For boiling to take place enthalpy of vaporisation > 0
Gas to liquid or vice verse
Sublimation is solid to gas and deposition is gas to solid but sublimation can also be used
Define enthalpy of fusion (not spec)
Latent heat of fusion = the energy a solid absorbs when it melts. It’s the change of enthalpy of a quantity of substance resulting from provision of heat that results in NO TEMP change. Constant pressure. Always endothermic
Change in energy to change a substances state from SOLID TO LIQUID
Define enthalpy of vaporisation (not spec)
Latent heat. Amount of enthalpy per mole of substance that must be added in changing a substances state from LIQUID TO GAS with no temperature change. Always endothermic
latent heat of condensation would be the opposite (negative sign)
What is a latent heat
Energy absorbed or released during a constant temperature process. A specific latent heat is for a certain mass
What determines melting or freezing point
Phase changes are an intermolecular process. No covalent bonds are broken. The bond enthalpy of a compound do not matter.
Ionic/metallic > Hydrogen > Dipole dipole > London
Stronger forces = higher melting/freezing point
Metals have high bp/mp closer to ionic compounds and sometimes higher. Tungsten has the highest at 3695K. The reason is that despite the bond between 2 atoms being weaker than ionic. the bonding is between every single electrons and the net effective attraction is strong.
What determines melting/freezing point and condensing/boiling point
Phase changes are an intermolecular process. No covalent bonds are broken. The bond enthalpy of a compound do not matter.
Ionic/metallic > Hydrogen > Dipole dipole > London
Stronger forces = higher melting/freezing point
Metals have high bp/mp closer to ionic compounds and sometimes higher. Tungsten has the highest at 3695K. The reason is that despite the bond between 2 atoms being weaker than ionic. the bonding is between every single electrons and the net effective attraction is strong.
melting point of metals across a period
They increase as atomic radius decreases due to increasing charge and more delocalised electrons per positive metal cation.
Melting and boiling points of organic compounds
Longer carbon chain is equal to higher melting and boiling points as London forces are proportional to surface area and more molecular weight equals ore forces.
Branching DECREASES surface area so decreases melting and boiling point
Organic lower than ionic or metallic hundreds to couple thousand kj
Describe the structure of a solid
Tightly packed particles which retain their shape
not free to move
vibrate in place
ordered repeating pattern in crystalline solids
Describe the structure of a liquid
Free to move but retains a nearly constant volume
Loosely packed, touching and fills container (conforms to fill/takes shape of container)
Describe the structure of a gas
Packed loosely and fills the container
Expands to fill
Composition of dry air
78% Nitrogen
21% oxygen
1% other gases like argon, CO2 etc.
- 80:20 N2:O2
Fractional distillation of air describe it
-190C : Gaseous nitrogen out at the top
Liquified air in at -200C
-185C : Liquid Oxygen out at the bottom
After air is filtered to remove all dust it’s cooled in stages to -200C at which point it’s a liquid
As it cools the WATER VAPOUR CONDENSES and is absorbed using absorbent filters
CO2 freezes at -79C and can be removed
O2 liquifies at -183C, N2 at -196 degrees - so the bottom of the column is hot enough to condense oxygen but nowhere in the column is it hot enough to condense nitrogen. It just rises and is removed.
Flouride in drinking water
Flouride in water prevents both decay and increases rate of remineralisation. Decay occurs when trace amount of acid react with the enamel and dissolve it (demineralisation). Acid is neutralised by saliva and the minerals reenter the enamel (remineralisation). Flouride reduces the ability of plaque bacteria to form acid and alters the structure of young children enamel so that its resistant to bacteria.
Chlorine in water
Kills bacteria and microbes (cholera, dysentry, typhoid) as it’s highly toxic.
Cl2 + H2O -> HClO + HCl
Carbon Dioxide effect on the environment?
source? Combustion of fossil fuels, deforestation.
Short wavelengths of visible light from the sun pass though a transparent medium but longer wave lengths of infrared radiation are unable to pass back through. The earth emits IF short wavelength and these are absorbed by greenhouse gases which reemit them as longer wavelengths which are unable to to except.
CH4 effect on environment
Livestock agriculture, decay or organic waster in landfill sites. Greenhouse gas
Carbon monoxide effect
Incomplete combustion of carbon counting fuels
toxic and binds to haemoglobin favourably preventing sufficient supply of oxygen
CO2 effect
From combustion, ocean absorbs CO2 and cause acidification from the formation of carbonic acid this dissolves animal shells made from calcium carbonate
Ca(2+) + Co3(2-) reversible CaCO3
CO2 effect
From combustion, ocean absorbs CO2 and cause acidification from the formation of carbonic acid this dissolves animal shells made from calcium carbonate
Ca(2+) + Co3(2-) reversible CaCO3
So2 effect
Burning hydrocarbons containing sulphur compounds creates H2S which reacts with oxygen to from sulphur dioxide which reacts with water to form sulphuric acid
No2 effect
N2+O2 -> 2NO
2NO + O2 -> 2NO2
NO2 + H2O -> HNO3 + NO
produced in car engines
If an increase in temperatures causes both an increase in yield and an increase in rate of reaction what kind of reaction is it
It is an ENDOTHERMIC. If increasing the temperature results in higher yield then that must mean the enthalpy change is negative. I.e. the reactions takes energy in from the surroundings.
If an increase in temperatures causes a decrease in yield and an increase in rate of reaction what kind of reaction is it
It is EXOTHERMIC. if an increase in temperature causes a decrease in yield that means that the enthalpy change is positive i.e. the reaction releases heat into the surroundings when it happens so increasing the temperature will not encourage this reaction.
What does increasing the temperature do to the rate of reaction
Increasing temperature always increases the rate of reaction. Increasing the rate of reaction does not indicate anything about the position of equilibrium. Increasing the rate of reaction concerns how fast a system reaches equilibrium not where that equilibrium lies. Increasing temperature promotes both the forward and the backwards reaction until they are occurring at the same rate (equilibrium)
What things affect rate of reaction
Temperature, pressure, concentration, surface area and catalyst
If increasing the pressure causes an increase increase in rate of reaction but does not change the yield what does this say about the reaction
The moles of gas of product is the same as the moles of gas of reactants
If a strong and weak acid of the same concentration is allowed to react with the same amount of Mg strip will there be any difference in the time taken for the Mg to react completely
Yes, the concentration of the acids are the same but the strong acids dissociates completely whereas the weak acid will dissociate to a lesser extent so the concentration of X- or Y- will be different. The more concentrated acid will take less time to react
What kind of ionic compound will display the most covalent character (will most likely form a covalent bond)
Smallest cation with largest anion
More positive cation and more negative anion
How does the solubility of solids vary with temperature
The solubility of solids increases as temperature increases (usually)
How does the solubility of gases vary with temperature
The solubility usually decreases as temperature increases
