unit 2

Question 1

State what is meant by standard enthalpy change of neutralisation, ΔneutH d

Answer 1

heat energy released under standard conditions
2. (when) 1 mol of water is produced (by the reaction of acid
with alkali)

Question 2

Explain how, if at all, the enthalpy change of neutralisation obtained in
(b)(ii) would differ if the heat capacity of the calorimeter was included
in the calculation.

Answer 2

(because the calculation has not taken into account the) energy
required to heat the calorimeter/ the (total) heat capacity would be
greater
2. the value(of the enthalpy change of neutralisation) would be more
exothermic/more negativ

Question 3

, sodium hydroxide reacts with 1‑bromopropane to
form propene.
Name the type of reaction and a suitable solvent.

Answer 3

elimination
2. ethanol / alcohol

Question 4

Explain why iodine is more soluble in hexane than in water,

Answer 4

iodine has (only) London forces/cannot form hydrogen bonds
IP2 water molecules form hydrogen bonds (and London forces and
permanent dipoles)
IP3 hydrogen bonds are stronger than London forces/ the strongest
(intermolecular force)
IP4 hexane forms (only) London forces/cannot form hydrogen
bonds
IP5 London forces formed between iodine and hexane are similar
(in strength) to those (broken) in hexane/ iodine (so iodine 6 Iodine cannot form hydrogen bonds/ only forms weak London
forces with water so the (hydrogen) bonds between water molecules
cannot be broken (so iodine does not dissolve in water)

Question 5

Explain whether or not the mean titre value for strontium hydroxide would be
different from that for calcium hydroxide.

Answer 5

strontium hydroxide is more soluble than calcium hydroxide
15. (so) titre value would be greater(than that for calcium) or
reverse

Question 6

Explain how a catalyst increases the rate of this reaction.

Answer 6

provides an alternative pathway/route with a lower
activation energy
29. so a greater proportion of molecules have E>Ea/area under
the curve to the right of Ea increases
30. so a higher proportion of collisions are successful

Question 7

Suggest suitable reagents and conditions for the conversion of propene to
propane‑1,2‑diol.

Answer 7

potassium manganate(VII)/
potassium permanganate/KMnO4
3. acidified/cold/room temperature/dilute aqueous solution

Question 8

Suggest why the production of propenoic acid from propane‑1,2,3‑triol is
more sustainable than its production from propene.

Answer 8

from propene the starting material is crude oil which is nonrenewable/finite
5. from propane-1,2,3-triol, the starting material is from
biomass/uses a by-product/reduces waste from biodiesel
production
6. propane-1,2,3-triol route produces only water as unwanted
produc

Question 9

Describe how intermediate J is formed in the first step, naming the process
that occurs.

Answer 9

• heterolytic (bond) fission occurs (1)
• the (pair of) electrons in the C─Br bond are transferred to
  the bromine atom

Question 10

Give two reasons why this value, measured under standard conditions, is
different from the value obtained using bond enthalpy data.

Answer 10

he bond enthalpies are averaged over a (large) number of
compounds (1)
* bond enthalpies always refer to substances in the gas phase

Question 11

ompare and contrast the intermolecular forces involved when hydrogen and
ammonia liquefy, by describing how these forces are formed.

Answer 11

1both hydrogen and ammonia form London /
dispersion forces
* IP2 a temporary dipole forms in a molecule and induces a
dipole in an adjacent molecule
* IP3 the attraction (between the temporary dipoles) is small(er)
in hydrogen because the H2 electron cloud is not easily
polarised
Differences
* IP4 ammonia forms hydrogen bonds (because nitrogen is very
electronegative)
δ+ δ- :——
hydrogen bond
* IP5 Accept hydrogen bond forms between the nitrogen lone
pair and the (δ+) hydrogen (of a different molecule)
* IP6 ammonia liquefies more easily than hydrogen because
hydrogen bonds are stronger than London forces

Question 12

(c) Explain how the infrared spectra of methanol and methanal can be used to
distinguish between the two compounds, stating the relevant bond stretching
vibrations and their wavenumber ranges.

Question 13

Suggest how propane-1,2,3-triol makes disinfectants more viscous.

Answer 13

• propane-1,2,3-triol forms three hydrogen bonds per
  molecule (1)
• so the molecules are strongly attracted to each other (and
  to surfaces

Question 14

xplain why alcohol B has a higher boiling temperature than alcohol A.

Answer 14

(alcohol B has) stronger London forces
 (as) greater (contact) surface area
(between molecules)

Question 15

why yeild is low

Answer 15

secondary amine

Question 16

Discuss some aspects of the thermal stability of the anhydrous nitrates of the
elements in Groups 1 and 2 of the Periodic Table.
In your answer you should
* explain the trend in thermal stability of the Group 2 nitrates
* describe any differences in the products of thermal decomposition of the
Group 1 nitrates
* give equations for the thermal decomposition of sodium nitrate and of
magnesium nitrate.

Answer 16

thermal stability increases down Group (2)
 IP2: ionic radius / size of ions increases (down groups)
and
polarising power (of cations) decreases / charge remains the same/2+
 IP3: NO breaks less easily / requires more energy to break (down groups)
 IP4: LiNO3 decomposes like Group 2 nitrates
OR
Group 1 nitrates other than lithium form (metal) nitrite/
nitrate(III)/MNO2
 IP5: equation for thermal decomposition of NaNO3
 IP6: equation for thermal decomposition of Mg(NO3)2

Question 17

advanatge of high pressure

Answer 17

shifts the yeild but requires more energery

Question 18

Suggest two reasons why it is more profitable to carry out all four stages
at the same site, instead of using different sites for each stage in the
industrial production of ammonium nitrate

Answer 18

less work force ,less land lower transport costs

Question 19

Explain why calcium carbonate decomposes at a higher temperature than
magnesium carbonate, in terms of the charge and size of the cations.

Answer 19

 Size (and charge)
calcium ion / Ca2+ has a larger (ionic) radius than a
magnesium ion (but the same charge)
or
magnesium ion / Mg2+ has a smaller (ionic) radius / is
smaller than a calcium ion (but the same charge) (1)
 Polarising power
so calcium ion / Ca2+ causes less polarisation /
distortion
or
magnesium ion / Mg2+ causes more polarisation /
distortion (1)
 What is polarised
of the carbonate ion / CO32− / anion / negative ion /
C−O bonds / C=O bonds /CO bonds

Question 20

Descending the group from fluorine to iodine, the electronegativity of the atoms
decreases even though their nuclear charge increases.
Explain the trend in electroneg

Answer 20

atomic radius increases
or
distance between the nucleus and outer electrons
increases
or
there are more shells / energy levels of inner electrons
between the nucleus and the outer shell electrons (1)
 so there is less attraction (by the nucleus with a higher
charge) for the bonding electrons / shared pair of
electrons

Question 21

Explain the trend in the boiling temperatures of the hydrogen halides.

Answer 21

all hydrogen halides have London forces (and
dipole-dipole forces between molecules) (1)
 the strength of the London forces increases
as the number of electrons increases (so the
boiling temperature increases from HCl to
HI)
or
the strength of the London forces increases as
the polarisability of the molecules increases
from HCl to HI (1)
 (only) HF has hydrogen bonding (between
molecules) (1)
 hydrogen bonding is (much) stronger than
London forces / dipole-dipole forces (so HF
has the highest boiling temperature)

Question 22

The reaction between 2-bromopropane and potassium hydroxide takes place
under two different conditions:
* in aqueous solution
* in ethanolic solution.
Compare and contrast these two reactions.

Answer 22

IP1 –Similarity
Both reactions involve hydroxide ions / OH−
 IP2 – Type of reaction
Reaction with aqueous solution is substitution
and
reaction with ethanolic solution is elimination
 IP3 – Type of reagent
(OH− is a) nucleophile in aqueous solution
and
a base in ethanolic solution
 IP4 – Products
In aqueous solution propan-2-ol / an alcohol forms
and
in ethanolic solution propene / an alkene forms
 IP5 – Equation in aqueous solution
CH3CHBrCH3 + OH− → CH3CHOHCH3 + Br−
 IP6 – Equation in ethanolic solution
CH3CHBrCH3 + OH− → CH3CH=CH2 + H2O + B

Question 23

Give two reasons for the difference between the data book value and the
experimental value, other than referring to standard conditions.

Answer 23

heat loss (to the surroundings) (1)
 incomplete combustion (of ethanol) (1)
 some ethanol evaporates

Question 24

) State why no ∆fH d value has been given for oxygen

Answer 24

 oxygen is an element and in its
standard state

Question 25

State the meaning of the term electronegativity

Answer 25

the ability of an atom to attract a bonding/shared pair of electrons (in a covalent bond)

Question 26

) Compare and contrast the reactions of chlorine with * water * cold, dilute aqueous alkali * hot, concentrated aqueous alkali Include an equation for each reaction, stating the type of

Answer 26

1 all are disproportionation reactions (because chlorine is both oxidised and reduced) IP2 chlorine changes/is reduced from 0 to ‒1 (in Cl– in all reactions) IP3 Cl2 + H2O ⇌ HCl + HOCl IP4 Cl2 + 2NaOH → NaClO + NaCl + H2O IP5 3Cl2 + 6NaOH → NaClO3 + 5NaCl + 3H2O IP6 chlorine oxidised to +1, +1 and +5 shown in the appropriate reactio

Question 27

Explain the trend in the thermal decomposition of Group 2 carbonates going down the group

Answer 27

the temperature of decomposition of carbonates / thermal stability increases (down the group)  the size of the cation increases (but has the same charge)  (so) polarises the anion / carbonate (ion) less

Question 28

Suggest how the catalytic converter reaches this temperature

Answer 28

 hot gases from the engine warm up the catalytic converter

Question 29

Explain why sulfur and oxygen exist in different states by referring to the intermolecular forces involved.

Answer 29

both have London forces (only) * S molecules have more electrons / S is a larger molecule (than oxygen) / S electrons are more easily polarised

Question 30

) Concentrated sulfuric acid reacts with solid potassium chloride and with solid potassium iodide. Compare and contrast these reactions to show the difference in reducing ability of these two halide ions.

Answer 30

misty/steamy fumes of) HCl/hydrogen chloride Potassium iodide IP2 purple vapour/black solid and I2 /iodine IP3 bad eggs and H2S/ hydrogen sulfide OR yellow solid and S/ sulfur OR Choking gas and SO2/sulfur dioxide IP4 KCl is not a redox reaction and KI is a redox reaction / KCl cannot reduce sulfuric acid but KI can IP5 iodide stronger reducing agent than chloride

Question 31

Explain what is meant by the terms alcohol and primary.

Answer 31

contains the OH group/OH is the alcohol group * primary means the C bonded to the OH (group) is attached to 1 (or 0) alkyl group / carbon atom/ R group

Question 32

‘mean bond enthalpy’

Answer 32

energy required to break one mole of a ( specific) bond  in the gaseous phase/state and averaged over a number of compounds/ different molecules/different compounds/different molecules

Question 33

Explain the trend in boiling temperature of these halogenoalkanes by comparing the intermolecular forces involved.

Answer 33

London forces (and (permanent) dipole-(permanent) dipole forces)  iodine atoms are more polarisable (than chlorine or bromine)/ 1-iodopropane has more electrons (than 1- chloropropane and 1-bromopropane)  (resulting in) stronger / more London Forces (so more energy required to overcome these forces)  (despite) 1-iodopropane having the weakest (permanent) dipole / (permanent) dipole forces

Question 34

) Give one advantage and one disadvantage of using bioethanol in petrol

Answer 34

advantage: (it is produced from) renewable / sustainable (resources) or it produces fewer emissions (of CO2 / greenhouse gases)  disadvantage: it uses up land (that could be used for food production)/uses a food crop that could be eaten or it produces less energy (per mole / g)

Question 35

Explain why these conditions are used, by describing the effect of changing the temperature and pressure on rate of reaction, equilibrium yield and cost.

Answer 35

if temperature increases, rate increases (because more particles have energy greater than Ea) IP2 if temperature increases, yield decreases (because forward reaction is exothermic/ reaction moves in the endothermic direction) IP3 if pressure increases, rate increases (because particles are more crowded and) collision frequency increases) IP4 if pressure increases, yield increases( as there are fewer particles on the RHS of the equation) IP5 the catalyst allows the use of lower temperature/less energy (for the same rate) IP6 high pressure (and temperature) are very expensive

Question 36

how to improve yeild

Answer 36

use the unused products

Question 37

Fluorine 38.0 −188 Hydrogen chloride 36.5 −85 MethanolExplain the large variation in boiling temperatures, given the small range in Mr values.

Answer 37

: fluorine molecules only have London forces (instantaneous dipole-induced dipole) between them (as it has a symmetrical electron cloud/is a symmetrical/non-polar molecule.) * IP2: hydrogen chloride is a polar molecule as chlorine is more electronegative than hydrogen. * IP3: HCl forms permanent dipole-permanent dipole interactions in addition to London forces. * IP4: methanol contains a hydrogen attached to a small electronegative element so can form hydrogen bonds (in addition to permanent dipole-permanent dipole interactions and London Forces). * IP5: hydrogen bonds are the strongest intermolecular forces so take the most energy to break. * IP6: London forces are the weakest intermolecular forces, so fluorine has the lowest boiling temperature.

Question 38

Explain why bromine is a liquid but iodine is a solid at room temperature

Answer 38

Iodine has more electrons (per molecule) (than bromine) * so stronger London forces between molecules / I2 (mean a higher melting temperature for iodine)

Question 39

Explain the chemical reasons for the conditions used and why such a low initial yield is acceptable in the industrial process.

Answer 39

High temperature increases rate as more particles have E≥ Ea  IP2 Catalyst increases rate by providing alternative mechanism / catalysts lower activation energy  IP3 but high temperature reduces yield / moves eqm to LHS as reaction is exothermic  IP4 so (high) temperature (of 300°) is a compromise (between rate and yield)  IP5 high pressure increases the yield as reaction / equilibrium moves to side of fewest particles / high pressure increases rate as more particles in the same volume  IP6 (low yield acceptable) as unconverted reactants can be recycled / passed through reactor again

Question 40

Explain why ethanol and water mix together fully

Answer 40

when they mix can form hydrogen bonds (to each other) (1)  as both compounds have hydrogen bonds (between their molecules) OR forces that form are similar in strength or stronger than hydrogen bonds in water / ethanol (1)  from the lone pair / slight negative charge on an oxygen (atom in one molecule) to a slightly positive hydrogen (atom in the other molecule) (on OH group or water)

Question 41

) Explain why the increases in the values of ΔcH are similar

Answer 41

each alkane differs from the next by -CH2/bonds broken and/or made increase regularly/

Question 42

Explain, with reference to their intermolecular forces, why the boiling temperatures of alkanes increase as the number of carbon atoms increases. A detailed description of the intermolecular forces is not required.

Answer 42

 the intermolecular forces are London / dispersion forces / instantaneous dipole – induced dipole forces  these forces depend on the number of electrons which increase (as the number of carbon atoms increase)  more energy is needed to break these intermolecular forces/to separate the molecules (so the boiling temperatur

Question 43

2‑bromobutane 29 2‑chlorobutane 75 2‑iodobutane <1 1‑bromobutane 41 2‑bromo‑2‑methylbutane 13 Explain these results by considering:  the chemical reaction occurring  the structures of the halogenoalkanes  the strengths of the carbon-halogen bonds.

Answer 43

(mechanism is nucleophilic) substitution  (Precipitation/precipitate of) silver halide forms  the time taken for the precipitate to form/rate of reaction depends on the carbon – halogen bond strength  Strength/bond enthalpy of the C-Halogen bond decreases going down group 7/any correct comparison of at least two Hal-C bond strengths (because the atomic radius increases)  The reactivity/rate of reaction of the bromoalkanes increases 1o < 2o < 3o/  1-bromobutane is 1o/2-bromobutane is 2o /2-bromo-2-methyl butane is 3o

Question 44

Describe the processes that occur when solid copper(II) sulfate dissolves in water.

Answer 44

(water molecules) break the (ionic) lattice/solid (1) * (water molecules) can hydrate/surround the ions / iondipole interactions form

Question 45

CH4 NH3 H2O HFExplain the differences in these boiling temperatures by considering all the intermolecular forces involved

Answer 45

IP1 methane has (only) London forces / dispersion forces / instantaneous dipole - induced dipole forces * IP2 London forces are weaker than hydrogenbonds * IP3 NH3/ H2O / HF have hydrogenbonds * IP4 the hydrogen bond is stronger in HF than H2O / NH3 or London forces are same/similar as they have the same number of electrons * IP5 Fluorine has higher electronegativity than N or O / is the most electronegative element/ H-F bond is the most polar * IP6 Water has more hydrogen bonds (than ammonia/ HF)

Question 46

) Compare and contrast the reactions of concentrated sulfuric acid with solid potassium chloride and with solid potassium bromide

Answer 46

both produce hydrogen halides (1) * formation of hydrogen halideis protonation (1) * both give offmisty/steamy fumes (1) Differences * only the reaction of potassium bromide is redox/bromide ions are stronger reducing agents than chloride ions (1) * (red)-brown fumes/liquid produced with potassium bromide (1) * sulfur dioxide/bromine given off with potassium bromide

Question 47

) Give two reasons why it is important to remove nitrogen oxides from the exhaust gases of diesel engines.

Answer 47

oxides of nitrogen dissolve in water to form acid rain/nitric acid * oxides of nitrogen cause breathing problems

Question 48

Explain, in terms of energy changes, why magnesium carbonate is insoluble in water

Answer 48

 large(r) amount of energy required to break ionic bonds (in lattice / MgCO3 / solid) (1)  small(er) amount of energy released during hydration (of ions) / when ions form bonds to water (1) OR Lattice energy is more exothermic

Question 49

Explain the trend in thermal stability of Group 2 carbonates.

Answer 49

Group 2 carbonates increase in (thermal) stability as you go down the group (1)  size of the (metal) ion increases / charge density (of ion) decreases (1)  so metal ion is less polarising or (electron cloud of) anion less distorted (1)  so weakens (covalent) bonds in carbonate ion less / more energy needed to break (covalent) bonds in carbonate

Question 50

Describe a chemical test and its positive result for the alcohol functional group in Y

Answer 50

add PCl5 / phosphorus(V) chloride /phosphorus pentachloride (1)  misty fumes evolved (that turn damp blue litmus red / form white smoke with ammonia) (1) OR  Add sodium / Na (1)  Effervescence / bubbles seen / fizzing

Question 51

) Explain why a saturated solution of calcium hydroxide is more alkaline than a saturated solution of magnesium hydroxide.

Answer 51

concentration of hydroxide ions is greater  calcium hydroxide is more soluble than magnesium hydroxide

Question 52

Explain why petrol is more miscible with biobutanol than with bioethanol.

Answer 52

biobutanol has a longer hydrocarbon / alkane chain/ more electrons than bioethanol (1)  so more/stronger London forces / dispersion forces / Van der Waals forces between biobutanol and petrol (than bioethanol and petro

Question 53

Samples of calcium and magnesium are added to separate test tubes of cold water containing a few drops of universal indicator. State and explain the differences in the observations made in each experiment.

Answer 53

Ca((s)) + 2H2O((l)) → Ca(OH)2((aq)) + H2((g)) * IP2: effervescence * IP3: (indicator) turns blue * IP4: faster / more vigourous reaction with calcium and linked to an observation OR no (observable) reaction with magnesium * IP5: Ca has lower ionisation energy OR Ca has more shielding / more shells / larger atoms * IP6: darker blue / more alkaline / higher pH with Ca and linked to greater solubility of Ca(OH)2

Question 54

Criticise the three students’ suggestions by linking the expected results, and the actual observations that would be made, for each test and the structures of the three alcohols.

Answer 54

1 potassium dichromate(VI) would go from orange to green (with menthol and citronellol but would stay the same / would not go green with linalool) IP2 menthol and citronellol are oxidised / react but linalool is a tertiary alcohol which is not oxidised by / does not react with potassium dichromate (so does not identify this –OH group) (potassium manganate(VII) is not a good choice because) IP3 potassium manganate(VII) would go from purple to colourless (with all three alcohols) IP4 (but would not identify the presence of the –OH group) as it also reacts with the C=C / reacts to produce a diol with linalool and citronellol / two of the alcohols Phosphorus(V) chloride is the best choice because) IP5 phosphorus(V) chloride will produce misty fumes (with all) IP6 (and identifies the presence of the –OH group in each as it) reacts with primary secondary and tertiary alcohols / reacts with all three alcohols

Question 55

Describe how London forces arise

Answer 55

instantaneous/temporary dipole and formed by asymmetrical distribution of charge/ random arrangement of electrons * (these produce) induced dipoles OR description of induction

Question 56

Compounds of lithium (Group 1) and compounds of magnesium (Group 2) have similar properties. Explain why: * the ionic radii of Li+ and Mg2+ are similar * the thermal decomposition of lithium nitrate is similar to that of magnesium nitrate but different from the thermal decomposition of sodium nitrate. Include relevant chemical equations in your answer.

Answer 56

IP1 magnesium has an extra shell than lithium (and as the charge on magnesium is Mg2+ and lithium Li+ ) so the ions are similar in size. IP2 equation for the thermal decomposition of lithium or magnesium nitrate. IP3 equation for the thermal decomposition of sodium nitrate. IP4 lithium and magnesium nitrate produce nitrogen dioxide but sodium nitrate does not/ or sodium nitrate produces a nitrite but lithium and magnesium do not IP5 because Mg2+ and/or Li+ are smaller than Na+ Or Mg2+ and/or Li+ have greater charge density than Na+ IP6 so polarise the nitrate ion/ anion more (causing Mg2+ and Li+ to thermally decompose in a similar manner) Must be a comparison. If there has been no mention of Na max 3 as only IP1, 2 and 5 can be awarded

Question 57

Typical conditions are 300°C and 60 atm with a catalyst of phosphoric acid. Explain why these conditions are used, by describing the effect of changing the temperature and pressure on rate of reaction, equilibrium yield and cost.

Answer 57

if temperature increases, rate increases (because more particles have energy greater than Ea) IP2 if temperature increases, yield decreases (because forward reaction is exothermic/ reaction moves in the endothermic direction) IP3 if pressure increases, rate increases (because particles are more crowded and) collision frequency increases) IP4 if pressure increases, yield increases( as there are fewer particles on the RHS of the equation) IP5 the catalyst allows the use of lower temperature/less energy (for the same rate) IP6 high pressure (and temperature) are very expensive

Question 58

Fluorine 38.0 −188 Hydrogen chloride 36.5 −85 MethanolExplain the large variation in boiling temperatures, given the small range in Mr values.

Answer 58

* IP1: fluorine molecules only have London forces (instantaneous dipole-induced dipole) between them (as it has a symmetrical electron cloud/is a symmetrical/non-polar molecule.) * IP2: hydrogen chloride is a polar molecule as chlorine is more electronegative than hydrogen. * IP3: HCl forms permanent dipole-permanent dipole interactions in addition to London forces. * IP4: methanol contains a hydrogen attached to a small electronegative element so can form hydrogen bonds (in addition to permanent dipole-permanent dipole interactions and London Forces). * IP5: hydrogen bonds are the strongest intermolecular forces so take the most energy to break. * IP6: London forces are the weakest intermolecular forces, so fluorine has the lowest boiling temperature.

Question 59

Explain why ethanol and water mix together fully.

Answer 59

when they mix can form hydrogen bonds (to each other) (1)  as both compounds have hydrogen bonds (between their molecules) OR forces that form are similar in strength or stronger than hydrogen bonds in water / ethanol (1)  from the lone pair / slight negative charge on an oxygen (atom in one molecule) to a slightly positive hydrogen (atom in the other molecule) (on OH group or water)

Question 60

Explain how each of the steps in this procedure is needed to show that the catalyst is not used up in this reaction.

Answer 60

heat to constant mass so all of the potassium chlorate(V) decomposes (1)  the solid product or potassium chloride dissolves (when the water is added) (1)  the rinsing removes potassium chloride (solution, which would otherwise add to the mass of the solid when it dries (1)  drying ensures the final mass recorded is only that of that catalyst (1)  the mass (of solid) recorded (at the end of the procedure) should be the same of that of the catalyst at the start

Question 61

Compare and contrast the reactions of concentrated sulfuric acid with solid potassium chloride and with solid potassium bromide

Answer 61

* both produce hydrogen halides (1) * formation of hydrogen halideis protonation (1) * both give offmisty/steamy fumes (1) Differences * only the reaction of potassium bromide is redox/bromide ions are stronger reducing agents than chloride ions (1) * (red)-brown fumes/liquid produced with potassium bromide (1) * sulfur dioxide/bromine given off with potassium bromide

Question 62

Propan-1-ol is heated with a concentrated solution of acidified potassium dichromate(VI). Explain how the conditions used affect the rate of the reaction and ensure that propanoic acid is the only organic product

Answer 62

The higher the concentration (of acid or Cr2O72-) the higher the rate 2. Because the collision frequency increases 3. The higher the temperature the faster the rate 4. Because more particles have an energy greater than the activation energy / more successful collisions 5. Excess / concentrated oxidising agent ensures complete oxidation 6. Heat under reflux ensures complete oxidation