R3 Flashcards

Question

Oxidation

Answer 1

A reaction in which a species gains oxygen, increases their oxidation state or loses electrons

Answer 2

A reaction in which a species gains hydrogen, decreases their oxidation state and gains electrons

Answer 3

Aqueous ions that remain unchanged in a reaction

Answer 4

A species that has the ability to accept electrons from another species, causing that species to be oxidised and itself to be reduced

Answer 5

A species that has the ability to donate electrons to another species, causing that species to be reduced and itself to be oxidised

Answer 6

The more reactive halogen/metal (greater (non-)metal tendency) will aim to be in its ion form, to create a complete octet on its outer shell

Answer 7

Chlorine - Yellow/Green Gas Bromine - Orange/Brown Liquid Iodine - Dark Grey Solid

Answer 8

A system in which a redox reaction occurs

Answer 9

An electrochemical cell that converts chemical energy into electrical energy through redox reactions ; Galvanic cell ; spontaneous

Answer 10

An electrochemical cell that converts electrical energy into chemical energy through redox reactions ; non-spontaneous

Answer 11

Anode is always where oxidation occurs whilst the cathode is always where reduction occurs ; The anode is always on the left whilst the cathode is always on the right ; In electrolytic cells the anode is positive (norm) whilst in voltaic cells the anode is negative

Answer 12

Half-cells to allow the electrons in the wire to be transferred and produce electrical energy ; To finish the circuit a salt bridge (normally KNO3) is needed which allows the positive ions in the salt bridge to move to the cathode (replacing the positive ions lost as they are turned into atoms) and vice versa ; Lastly in each half-cell an electrolyte containing the ions of the atom on the electrode is needed

Answer 13

A liquid juncture that allows for the movement of cations and anions in a voltaic cell, which completes the circuit needed for the cell to produce energy through the redox reaction.

Answer 14

Zn (s) | Zn2+ (aq) || Cu2+ (aq) | Cu (s)

Answer 15

They use reversible redox reactions ; For example a lithium battery ; At the anode Li (graphite) -> Li+ (electrolyte) + e- as the lithium atoms get oxidised ; The Li+ ions pass through the electrolyte towards the cathode where they then get reduced ; Li+ (electrolyte) + e- + CoO2(s) -> LiCoO2(s) ; These are the formulae for the discharge of the battery, when getting recharge the arrow simply swaps

Answer 16

H2 (g) -> 2H+ (aq) + 2e- 1/2O2 (g) + 2H+ (aq) + 2e- -> H2O (l)

Answer 17

Single-use battery, non-reversible reaction Rechargeable battery, reversible reaction Continuous reaction as long as fuel and oxidant are available

Answer 18

Long shelf life, low cost and high reliability High energy density and rechargeable Continuous reaction as long as fuel and oxidant are available

Answer 19

Lower energy density and environmental costs Can cause environmental impact, high cost or high maintenance depending on type Safety concerns and lack of fuel availability

Answer 20

Back-up power generation EVs Fire alarms

Answer 21

One container and is normally used to purify ores as you can collect the pure metal from its impure form ; The electrolyte needs to contain the molten form of the anode/cathode species ; Due to it being molten the products will mostly be molten

Answer 22

In aqueous solutions, the water can also be electrolysed ; At the anode 2H2O (l) → 4H+ (aq) + O2 (g) + 4e– pH decreases due to H+ ions At the cathode 2H2O (l) + 2e– → H2 (g) + 2OH– (aq) pH increases due to OH- ions Both equations are in the formula booklet Overall equation 2H2O (l) → 2H2 (g) + O2 (g)

Answer 23

Used as a reference to measure the standard electrode potentials of all other cells ; Conditions are 100kPa, 298K, 1.00moldm-3 of H+ ; Inert platinum electrode ; The hydrogen half cell given an E of 0V ; Depending on whether it's an anode hydrogen ions form hydrogen gas or vice versa

Answer 24

E(cell) = E(reduction) - E(oxidation) ; Not multiplied by the stoichiometry of the equation ; A positive E(cell) means its a spontaneous reaction ; This means that a more positive E value at reduction is favoured whilst a more negative E value at oxidation is favoured

Answer 25

The E value of water at reduction is greater than for most metal ions and so this reaction is favoured as it is a stronger oxidising agent, therefore producing hydrogen gas. This happens unless Copper, silver, gold or platinum ions are used as they are less reactive so more easily reduce into atoms ; The E value of water at oxidation and of halides are very similar and so what occurs depends on the concentration of the halide ions, a high concentration of halides means that the halogen gas will be produced and vice versa

Answer 26

When non-inert electrodes are used then the atoms from the anode will be stripped and passed to the cathode ; If the anode doesn't contain the same respective atom as the ions then the colour of the electrolyte will be lost (as the concentration doesn't remain the same)

Answer 27

The electrolytic coating of an object with a thin layer of metal

Answer 28

Gold-plated for aesthetics ; Iron is galvanised with zinc to prevent the rusting of iron ; The electrolyte needs to contain the same respective ions as the anode's atoms

Answer 29

Time the electrolysis is left on for ; the current supplied ; the charge on the ion

Answer 30

Q = It moles of substance = Q / (number of electrons x F)

Answer 31

Primary alcohols can undergo partial oxidation to aldehyde and complete oxidation to carboxylic acids with a catalyst of acidified potassium dichromate (VI), K₂Cr₂O₇, turning from orange to green, or acidified potassium manganate, K₂MnO₄, turning from purple to colourless ; For the aldehyde heat distillation can be used where the aldehyde is instantly evaporated and removed to avoid complete combustion as it has a lower boiling point than the alcohol and the carboxylic acid, due to no hydrogen bonding ; For the carboxylic acid heat reflux would be used where the condenser is vertical to allow any evaporated aldehyde to be condensed and fully oxidise to a carboxylic acid

Answer 32

Secondary alcohols fully oxidise to form a ketone under heat reflux ; Tertiary alcohols don't oxidise due to a lack of available hydrogens on the carbon atom that allows oxidation to occur

Answer 33

The opposite of the oxidation of alcohols can occur with catalysts this time of acidified sodiumborohydride (NaBH4) or acidified Lithiumaluminiumhydride (LiAlH4) where the carboxylic acid to the primary alcohol needs the LiAlH4 since it's a stronger reducing agent. Both catalysts need to be acidified to allow the nucleophillic attack (from the H- ion in the catalyset) to occur then a H+ ion to add on to the proton donating oxygen allowing to form an alcohol

Answer 34

The reduction of unsaturated compounds involves using H2 to react with them (hydrogenation) removing their unsaturated bond (2H2 needed for a triple bond) with a nickel catalyst at 180C

Answer 35

The formula uses n where n is the number of electrons (moles of electrons) not the moles of anything else

Answer 36

Reactive species or intermediate with an unpaired electron ; Made through the homolytic fission of a species

Answer 37

The breaking of a covalent bond breaks in such a way that each atom ends up with one of the electrons, forming two radicals

Answer 38

For certain bonds with weak bond enthalpies, UV light can be used to break the bond such as for Cl-Cl, Br-Br or O-O

Answer 39

CFCs normally form Cl radicals in the presence of UV light (sun) due to the C-Cl bond being longer and hence weaker then the C-F bond. This causes Cl. + O3 -> ClO. + O2 ClO. + O3 -> Cl. + 2O2 This not only breaks the ozone but also replenishes the Cl radical and so the cycle continues The radicals are able to break the bonds in O3 since they are delocalised so slightly less than O2's double bonds, which they cannot break

Answer 40

The first step that initiates the formation of a radical. The input of energy is required usually in the form of UV radiation or heat.

Answer 41

Alkanes are normally very unreactive due to their non-polar bonds and relatively strong bonds (relatively high bond enthalpy) and is the only reaction that alkanes undergo. It needs the initiation step (where the radical is formed), the propagation step (where the radical and the covalent species react to form a new radical and a new covalent species causing a chain reaction) and the termination step (where two radicals come together to form one new covalent species) ; Beware that many species can occur through the halogenoalkanes or longer chain alkanes through two radical alkyl groups being formed and joining together

Answer 42

An electron-rich species that aims to donate a pair of electrons (Lewis base) whilst gaining a nucleus

Answer 43

The nucleophile attacks a carbon that is attached to a halogen (leaving group) that causes both electrons from the C-X bond to go onto the X forming an X- ion whilst the nucleophile provides a pair of electrons and forms a bond with the same carbon C-Nu

Answer 44

An electron-deficient species that aims to accept a pair of electrons (Lewis acid) whilst losing a nucleus

Answer 45

The molecule that is attacked by the nucleophile in a reaction

Answer 46

The breaking of a covalent bond in such a way that one atom takes both of the shared electrons, creating a negative ion (anion) and a positive ion (cation) ; It happens due to a difference in electronegativity of above 0.4

Answer 47

The process of an electrophile being added to an electron rich area

Answer 48

The pi electrons in the electron-rich area repel the shared electrons in the X-X bond causing an induced dipole in the X-X causing one to be more electronegative than another so heterolytic fission occurs causing the addition of both (Bromine water test in alkenes)

Answer 49

The difference in electronegativity between the H and X causes the heterolytic fission and the rest occurs after

Answer 50

The difference in electronegativity between the O and the H in the water molecule causes the heterolytic fission into a H and an OH, the rest following on from that

Answer 51

In the asymmetrical alkenes to carbocations can be formed forming a major and minor product. The favoured and more stable carbocation can be seen by viewing which has the most electron releasing alkyl groups, decreasing the charge on the carbon and making it more stable (positive inductive effect). The more stable one will lead to the major product.

Answer 52

In primary halogenoalkanes, there is little steric hindrance since the nucleophile can attack from the rear, rear-side attack, which causes an inversion of configuration (therefore it's also a stereospecific reaction) but also means that the reaction occurs in one step and the rate is dependent on the ability of the X group to leave and the nucleophile to join so depends on two molecules so is. bimolecular. It also has a transition state that has both on it simultaneously and has a molecular/electron-domain geometry of trigonal bipyramidal

Answer 53

The prevention or delay of a chemical reaction occurring due to the presence of a bulky group which has a large atomic radius.

Answer 54

In tertiary halogenoalkanes there is very large steric hindrance so then X first has to leave (which is the slowest and rate-determine step and only relies on the X leaving group hence why it's unimolecular) before the nucleophile can join in that same position. The nucleophile however can join from any position so enantiomers can form but due to the probability of attacking from any direction is the same a racemic mixture is formed. The tertiary carbocation is also more stable due to the positive inductive effect which allows it to be an intermediate and no a transition state

Answer 55

A leaving group is a better leaving group and hence the rate will be lower if the bond is weaker. In halogens this occurs when you go down a group as the ability to attract a pair of electrons decreases. This decrease in the covalent bond strength means its easier to break heterolytically so it will be a faster rate of reaction

Answer 56

As previously discussed due to benzene's delocalised structure it doesn't undergo electrophilic addition but instead electrophilic substitution with nitrate ions (which are formed via nitric and sulphuric acid reacting together H2SO4 + HNO3 <-> HSO4- + H2NO3+ H2NO3+ <-> NO2+ + H2O) Then the benzene donates from it's electron rich region (inside the ring) to the NO2+. This first step causes a horseshoe positive benzene ring with both a H and a NO2 group attached. However, the C-H then breaks heterolytically causing the shape to return to neutral and the aromatic ring with the NO2 group instead of the H atom

Answer 57

An electron-pair acceptor

Answer 58

An electron-pair donor

Answer 59

Due to the electron pairs being accepted/donated, coordinate bonds are formed. This is especially notable in forming complex ions where the ligands are the lewis bases whilst the central metal ion are lewis acids

Answer 60

The total amount of coordinate bonds formed (can be two from the same species)

R3 Flashcards

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