New A-level 2015
The revision guides are split into physical, inorganic and organic chemistry. There are no modules. The AS only topics are labelled AS.
Physical Chemistry
1.1 revision guide Atomic Structure AQA (AS) (updated February 2021 )
1.2 revision guide Calculations AQA (AS) (updated October 2023 )
1.3 revision guide Bonding AQA(AS) (updated January 2022 )
1.4 revision guide Energetics AQA(AS) (updated April 2020)
1.5 revision guide Reaction Kinetics AQA (AS) (updated February 2023)
1.6 revision guide Equilibria AQA(AS) (updated January 2022 )
1.7 revision guide Redox(AS) (updated November 2018)
1.8 revision guide Thermodynamics AQA (updated February 2023)
1.9 revision guide Rate Equations AQA (updated October 2023 )
1.10 revision guide Equilibrium Constant Kp AQA (updated October 2023 )
1.11 revision guide Electrode Potentials AQA (updated January 2022 )
1.12 revision guide acid base equilibria AQA (updated January 2022 )
Inorganic Chemistry
2.1 revision guide periodicity (AS)(updated December 2019)
2.2 revision guide Group 2 AQA(AS) (updated February 2024 )
2.3 revision guide Halogens AQA (AS) (updated January 2022 )
2.4 revision guide Period 3 AQA (updated February 2023)
2.5 revision guide Transition metals AQA (updated October 2023 )
2.6 revision guide Reactions of Aqueous Ions AQAA (updated October 2023 )
Organic Chemistry
3.1 revision guide introduction organic AQA(AS) (updated February 2021 )
3.2 revision guide Alkanes AQA (AS) (updated October 2023 )
3.3 revision guide Halogenoalkanes AQA(AS) (updated February 2021)
3.4 revision guide Alkenes AQA(AS) (updated February 2023)
3.5 revision guide Alcohols AQA(AS)(updated February 2021)
3.6 revision guide Organic Analysis (AS) (updated December 2019)
3.7 revision guide naming and isomerism (updated February 2021)
3.8 revision guide Aldehydes and Ketones AQA(updated January 2022 )
3.9 revision guide Carboxylic acids and derivatives AQA (updated February 2024)
3.10 revision guide Arene Chemistry AQA (updated October 2023 )
3.11 revision guide Amines AQA(updated January 2022 )
3.12 revision guide polymers AQA (updated April 2020)
3.13 revision guide amino acids proteins and DNA AQA (updated May 2023)
3.14 revision guide Organic Synthesis AQA (updated February 2023)
3.15 revision guide NMRR (updated October 2023 )
3.16 revision guide chromatography(updated December 2019)
AQA mechanisms summary AS (AS) (updated February 2021 )
AQA mechanisms A level summary (updated February 2023 )
Practical Guide AQA (updated October 2023 )
chemrevise 
also for chem 4 june 11 Q5ei, how do you know it’s Rate = k[DEP] rather than Rate = k[H2O]?
besides the clue they’ve given in the question saying ‘using DEP’ to represent the ester’
It’s the ‘excess’ bit. If you have two reactants and one is in excess then any change in rate will be due to the reactant not in excess.
I don’t think the following equation is balanced:
CH3CO2H + Na CH3CO2-Na+ + H2
I think there should be a 2 in front of CH3CO2, Na and CH3CO2-Na+ as the hygrogens aren’t balanced.
This i for carbonyl compounds, page 4
Apologies if I am wrong
well spotted- will change
Is there any ISA/EMPA on unit 2 guide that I dont have to revise for unit2 exam? Please let me know which pages !!! Thank you
There are not whole pages to miss out for module 2. I have known the same practical type questions come up on module 2 paper and ISA’s
Does it matter if the equations are perfectly correct for extraction of metals because some books say that for this equation Fe2O3(s) + 3 C(s) 2 Fe(l) + 3 CO(g) co2 is meant to be formed instead of CO
I have not tried to give every possible equation you could be asked. Both are correct. You just need to read the question carefully to work out which would be the correct one.
Okay also for the conditions for each metal extraction does it have to be exact? Do we even need to know the temp for each extraction for each metal?
No – generally high temperature is enough detail
In the mark scheme in unit 2 chem there was a question-
Write an equation for the reaction of chlorine with water in bright sunlight.
the answer in the mark scheme is 2Cl2 + 2H2O —->4HCl + O2
However is it alright to write 2Cl2 + 2H2O —–> 4H+ 4Cl- + O2
yes
Hi, can you please explain why you don’t have to write OH- on question 5ei of the June 2011 chem 4 paper even though it is a hydrolysis reaction 🙂
The question said ‘Hydrolysis of DEP in an excess of water was found to follow first order kinetics.’ You should deduce from this that the order of the OH- ions is zero order and so should not be included in the rate equation
What is the name of the shape CCl2?
It is ‘bent’. It should have two bond pairs and only one lone pair though so not exactly the same as the water bent molecule
why electrolysis not used if metal has to be pure
Thanks
I expect the molten metal that comes out will have some of the ore or reactants still dissolved in it in small amounts
the unit 2 metal chapter has equation
Fe2O3(s) + 3 C(s) 2 Fe(l) + 3 CO(g)
however in my book the product is Co2 instead of Co
So are both equation correct??
Thanks
I have not tried to give every possible equation you could be asked. Both are correct. You just need to read the question carefully to work out which would be the correct one.
Also, are all elements perfect crystals at absolute zero and therefore have zero disorder/entropy?
Thanks
Hi,
I was wondering for unit 4, do we need to know if elimination forms major and minor products (if the double bond can form in two different places), like for electrophilic addition? If so, what’s the rule for which is major/minor?
Also for periodicity of period 3 elements, on pg 3 shouldn’t it be MgO is better than NaOH rather than Mg(OH)2 is better than NaOH, as this is what it said on Q1e on this paper:
Click to access AQA-CHEM5-QP-JUN12.PDF
?
Thanks!
I was just wondering on the mod 4 revision guide 4. naming and isomerism the last page, when it talks about forming a racemic mixture by nucleophilic addition and shows the mechanism. How can that be a racemic when it has two CH3 groups on it? Doesn’t that disqualify it as an optical isomer?
yes indeed
can you also please yell the difference between magnetic field and electric field (for peson who hasnt done physics) in respect to mass spectrometer
Well an electric field is caused between two plates with a potential difference or voltage between them. Think what you might feel sticking your finger in an electric socket. A magnetic field a field caused by a magnet. Think about picking up paper clips with a magnet.
Another question
Is dipole dipole bonding same as permanent dipole dipole bonding
yes unless the word temporary is used
In the bonding chapter (unit 1 )- Is it ok when you are explaining the shape you refer to lone and bond pair INSTEAD of lone pair of electrons and bond pair of electrons
Furthermore is electron pair and (lone pair/bond pair) same ???
Well if you can remember the ‘electron’ pair bit don’t leave it out.
Hi, I just had some confusion on questions on entropy:
For Q3 a), b) and c)ii, when do you write deltaG<0, and when do you write deltaG<=0; or is it safe to always write deltaG<=0 on all explanation questions about feasibility?
Click to access AQA-CHEM5-QP-JAN13.PDF
Click to access AQA-CHEM5-W-MS-JAN13.PDF
Thanks!
It’s always safe to write deltaG<=0
hi sir,
for the primary Lithium –manganese dioxide cell- non rechargeable why was a Pt solid used? isnt there already a solid present? ( MnO2 (s) , LiMnO2(s) )
thank you
They are not conducting solids though.
On Module 1 (Amount of Substance) Is the last 2 pages for the ISA? I don’t remember learning about titrations in depth and was wondering if I need to know them for the AQA unit 1 exam? Thanks alot! 🙂
That’s mostly ISA/EMPA material
Thank You! I just had my unit 1 exam a few days ago, and it went quite well.
I only used these notes to revise and past papers, and didn’t need anything else because they are so fantastic!
Thank you so much!!
I have my unit 2 exam in a week, and was wondering if there is any ISA/EMPA pages in your module 2 notes that i can leave out and not revise? If so which ones? Thanks alot
There are not whole pages to miss out for module 2. I have known the same practical type questions come up on module 2 paper and ISA’s
I think there might be a mistake on Mod5 redox bottom of page 2, its says “It is not possible to measure the absolute potential of a half electrode on its own”, do you mean a half cell rather than a half electrode? or do the 2 terms mean the same thing?
They mean the same thing
thanks for the clarification.
Another question… i am slightly confused about the overall reaction for the lead acid cell, shouldn’t it be 2SO4^2- rather than just 1 of them?
thanks again for all the help
Hi,
Is there another link to the downloads for these revision guides that doesn’t take you to a file sharing site? I’m studying AS Chemistry AQA at a boarding school and they have blocked these types of websites! 🙂
sorry the files are just on the wordpress server. I suggest you speak to your IT support
They’ve sent me the files now. Thank you so much for posting these! 🙂
Quick question about enthalpy of solution. The CGP book has a similar definition to yours but it doesn’t talk about the dissolved ions being well separated and so do not interact with each other, it states that the the 1mole solute is dissolved in sufficient solvent that no further enthalpy change occurs on further dilation.
So which approach would be more likely to gain the maximum marks? i couldn’t find a definition question for this in previous papers so i believe there is a good chance it will come up this year.
I think both definitions are basically saying the same thing. I can’t remember now where I got my definition from. I’m sure both would be fine but you could combine them together if you wanted to be super sure.
Hi, I have a confusion with covalent character. In the thermodynamics guide you said if something is ionic with covalent character, it tends towards giant covalent and has a stronger lattice than if it were 100% ionic, so it should have a higher melting point; but then in period 3 periodicity, (my other books say) Al2O3 has a lower melting point than MgO because of covalent character- so there seems to be an inconsistency?
Thanks!
There are many inconsistencies in chemistry! I expect there are some cases where things that have covalent character will tend towards a more molecular structure. You will have to look at the data presented in the question and think which case it might be.
Hi, thanks for these notes!
I just have a couple of questions on module 5 redox equilibria.
1) On page 6 for the primary lithium-manganese dioxide non-rechargeable cell, does it matter which order the Li+(aq) and MnO2(s) (on the right hand side of the cell diagram) go in? Because if anything shouldn’t the MnO2(s) go nearest the centre double line as the oxidation state of Mn in it (+4) is higher than that of lithium in Li+ (+1)?
2) Are both fuel cell reactions (in both alkaline and acidic conditions) exothermic and therefore produce H2O + heat from the outlet?
3) Are all Ecell values positive?
Thanks!
1) For this I have used the representation exactly as used by AQA (mod 5 Jun 10). I think it would be acceptable to swap the Li+ and MnO2 around because they are on the same side of the equation.
2) Yes they would both be exothermic
3) Ecell can be positive or negative depending on which way around the electrodes were. You would choose to generally make it positive.
1) Do we need to know about shapes of certain complexes being “elongated” octahedral or “distorted” octahedral?
2) For mod 5 guide 4 pg 9 reactions of inorganic compounds with excess OH- is it ok to write [Al(OH)4]- as [Al(H2O)2(OH)4]-?
3) For the same section as Q2 above, in excess OH-, do the OH-s now act as ligands to substitute 1 or 3 H2Os (with Al and Cr respectively) or is it further deprotonation, and do we need to know this?
Thanks!
hi, I was just reading through the mod 5 periodicity guide and just wanted some clarification if you wouldn’t mind. On the second page, about the reactions of period 3 elements with oxygen, it says that Mg, Al etc. react with Oxygen with a white flame, and produce white solid smoke ? I’m just confused over the last part, is it meant to say white solid AND smoke , or do we quote it as it already is in the exam and say “white solid smoke”, because it isn’t making sense to me. Thanks
smoke is solid particles in the air. So all smoke is solid and not to be confused with vapours or fumes which are gases.
Is it the same case for ethanedioate ions (as for ethane-1,2-diamine) in that we don’t need to know whether it substitutes fully or partially? or does it only substitute partially when e.g. dilute?
Thanks
I would assume it completely substitutes unless the question suggests otherwise. As long as you can be flexible you will be fine.
Hi,
Thank you so much for these notes! They are really good. I just wanted to ask whether these notes alone are sufficient, or would I have to use the AQA textbook alongside them?
It depends how well you understand the material. I would say use more than one source. I do cover all the material though.
if 1,2-diaminoethane is in limited amount a base and in excess a ligand, like ammonia, is there also an exception with copper where it doesn’t fully substitute in excess and forms [Cu(NH2CH2CH2NH2)2(H2O)2]2+, but fully substitutes with chromium and cobalt to form [M(NH2CH2CH2NH2)3]2+?
Thanks
but in mod 5 guide 4 p11, you’ve shown it as fully substituting with copper when in excess?
Don’t worry in this case whether it is fully or partially substituted. These are not facts you’re meant to learn. When it has come up in questions there has been information in the question which are meant to read and interpret to workout the formulae.
Hi, firstly thanks so much for these great notes, I’m sure many people have benefitted greatly. I just wanted to ask about the “organic techniques” section at the bottom of your “mod 4 revision guide 10 -synthetic routes”. Do we need to know all these techniques for the CHEM4 exam (ie. could they ask us any questions about these techniques), or have you included these for practical exams/isas? Thanks in advance, id really appreciate your help 🙂
They are for ISA’s and EMPA’s on the current syllabus really.
Hi, I was wondering how do you know when 1,2-diaminoethane acts as a base and when it acts as a ligand, in reactions with each of the complexes we need to know?
Thanks
It’s like ammonia- in limited amount a base and in excess a ligand
Quick question regarding transition metal chemistry, do the other transition metals like Fe3+ and Fe2+ make tetrahedral complexes when you add conc HCl?
I think Fe3+ does but not Fe2+. You don’t need to know this although one could imagine an application question where you might be asked to work out the formula
Hey!
Thanks for all your resources. They’re amazing.
I was wondering if you could help me on the following question: “Using complex ions formed by Co2+ with ligands selected from H2O, NH3, Cl–, and EDTA4–, give an equation for each of the following. iii)A ligand substitution reaction which occurs with no change in the co-ordination number but a change in the charge on the complex ion.”
Would it be correct to have the following answer:
[CO(H2o)4(OH)2]
This is a change in the charge ( from 2+ to 0) but no change in co-ordination number.
Your answer is not correct because that reaction is not a ligand substitution but a deprotonation reaction. You are correct that the charge has changed but not the coordination number but it isn’t ligand substitution.
Use the edta4- ion reaction.
Hi, I have a few quick queries:
1) for reducing the [Cr(H2O)6]3+ into [Cr(H2O)6]2+, for the equation, again is it ok to just use Cr3+ reactant and Cr2+ product?
2) also for the 2 individual equations making up the chromate/dichromate equilibrium, is it better to write them as
Cr2O72- + OH- —> 2CrO42- + H+ and 2CrO42- + H+ —> Cr2O72- + OH-
or
Cr2O72- + 2OH- —> 2CrO42- + H2O and 2CrO42- + 2H+ —> Cr2O72- + H2O
?
3) If we wanted to turn dichromate into say Cr(H2O)3(OH)3, would the first step have to be FeSO4 and HCl (to prevent further reduction into Cr2+) or would it still be acceptable to use zinc and HCl?
Thanks very much!
1) yes fine to use Cr3+ and Cr2+ for writing redox reactions as well as [Cr(H2O)6]3+. You have to use your judgement though. Does it look like the question is more about redox or complex ions.
2) Use second set of reactions where H2O is formed.
3) If you want to stop at Cr3+ it is best to use Fe2+ because it is not strong enough a reducing agent to reduce the Cr3+ to Cr2+
thanks for the help chem revise
In calculations topic when balancing ionic equations can’t you just add electrons instead of numbers in front of the charged species? And also for energetics topic if theres two solutions do you always use both their volumes for the q=mct but only the one with fewer moles when you calculate kj/mol? Because the example with hcl and naoh contained same number of moles so it was a little difficult to understand
In a full redox equation there should be no electrons. Electrons only appear in half equations.
Yes is the answer to your second question.
Hi, thanks for these notes! I was wondering for transition metals when oxidising in alkaline solution, is this only for H2O2 oxidation, and not oxidation with O2/in air?
Also what would be the half equation for Co(OH)2(H2O)4 —> Co(H2O)3(OH)3 when it’s oxidised with oxygen? is it the same as when it’s with H2O2 (
Ox:Co(H2O)4(OH)2 +OH- ——> Co(H2O)3(OH)3 + e- + H2O), but then isn’t it also in alkaline solution because of the OH- in the reactants, but in my book it says ‘in air’ only?
Thanks very much!
Yes it is fine to use the same half equation for oxidation by oxygen and hydrogen peroxide
Hi , I have a quick query about carrying answers through – say I rounded 1.0948667678 to 1.09 for my answer to part 1 and in part 2 of the question I had to use my part 1 result to get another value, do I carry forward the exact number or the rounded answer .the reason i ask is because using a rounded answer introduces rounding inaccuracies . However would I still get error carried forward (in case of a mistake) if I carried forward the non rounded number instead of the rounded number which technically was he final answer for part 1
Numerical answers in exams always allow a range of answers that will compensate for rounding off in earlier parts- just don’t go below 3 sig figs to be on the safe side.
oh ok thanks but say I do get 1.0948667678 and round to get my final answer to part 1 to 1.09. If this turned out to be a mistake , would I still get error carried forward marks for part 2 if i carried forward the full string of decimal places(i.e 1.094866…) or is it required to get error carried forward that you only use the final answer you provided (i.e. the rounded one of 1.09)
Sorry to be such a pain in the neck I just want to be absolutely sure – thanks again for the help
Either is fine
Hi, thanks again for the notes; I just have a couple of questions on variable oxidation states in transition metals (mod 5 guide 4 pg3):
1) For the chromate/dichromate equilibrium, do we have to learn the individual equations for when you add an acid to chromate or alkali to dichromate?
2) For reducing the dichromate ion into [Cr(H2O)6]3+/[Cr(H2O)6]2+, in the exam should we write the reduction equation as forming [Cr(H2O)6]3+/[Cr(H2O)6]2+ as the product or just Cr3+/Cr2+, because I noticed you had shown the latter; (but for the oxidation of [Cr(OH)6]3- into [CrO4]2-, you showed the equation using the [Cr(OH)6]3- reactant rather than just Cr3+ as a reactant)? is there a general rule for the exam of which way to show it?
Thanks
For 1) you should be able to work these simple equations out rather than learning them individually.
For reducing the dichromate ion into [Cr(H2O)6]3+/[Cr(H2O)6]2+, it is sufficient to write Cr3+/Cr2+ but if you prefer to use [Cr(H2O)6]3+/[Cr(H2O)6]2+ then do so.
for the oxidation of [Cr(OH)6]3- into [CrO4]2-, it is important to put as [Cr(OH)6]3- because this is not the same thing as [Cr(H2O)6]3+/ Cr3+
Thanks,
1) for reducing the [Cr(H2O)6]3+ into [Cr(H2O)6]2+, for the equation, again is it ok to just use Cr3+ reactant and Cr2+ product?
2) also for the 2 individual equations making up the chromate/dichromate equilibrium, is it better to write them as
Cr2O72- + OH- —> 2CrO42- + H+ and 2CrO42- + H+ —> Cr2O72- + OH-
or
Cr2O72- + 2OH- —> 2CrO42- + H2O and 2CrO42- + 2H+ —> Cr2O72- + H2O
?
3) If we wanted to turn dichromate into say Cr(H2O)3(OH)3, would the first step have to be FeSO4 and HCl (to prevent further reduction into Cr2+) or would it still be acceptable to use zinc and HCl?
Thanks!
Hello,I was confused when I came across this question. How would you approach this question if you don’t know what the product would be?
Describe the colour change that you would observe when an aqueous solution of iodine, to which starch solution has been added, reacts with an excess of Na2S2O3. Write an equation for the reaction that occurs between iodine and Na2S2O3.
Thank you for your help.
This is not an aqa question- not on the syllabus. It could be an edexcel questions. See bottom of page 10 of https://chemrevise.files.wordpress.com/2015/04/3-group-2-and-group-7.pdf
Thank you so much for your amazing notes- they’re really helping through my A2 revision! Just wondering if there is likely to be a revision guide for Unit 5 inorganic ions in aqueous solution before the exam? Thank you!
It is included in the transition metal notes
Sir please could you help me with understanding how temperature would effect the E cell value. Am i right in assuming that Li(+)+e===Li(s) is exothermic in the direction of reduction. Please clarify.
Are the notes on “organic techniques” half way through mod 4 guide 10 for EMPA papers specifically or should we revise them again (like measuring melting point) for the main exams?
Thanks!
meltingpoint is mainly for the practical exams
And is it the same for purifying organic substances and boiling point?
The organic techniques section is mostly for ISA EMPA
spec – “know that transition metal characteristics of elements
Ti – Cu arise from an incomplete d sub-level in atoms or ions”
notes refer to sc-cu is this still correct?
I have an issue with Sc. My issue is with the AQA definition of a transition metal which I think is the official IUPAC definition. As far as I can see the Sc fits the definition of an incomplete d orbital in atoms or ions because it has a 3d1 structure in its atom form. I don’t think it’s an important point. I can’t find a question about it in the past 15 years.
If you look at other exam board definitions they still use the definition of an incomplete d orbital in the ions, which definitely excludes Sc
Hi, is [Fe(H2O)6]3+ yellow or violet? It says yellow in the 3+ ion summary but violets when the metal aqua ion is introduced on page 9 of the transition metals topic.
Both are acceptable. See page 2 on this file https://chemrevise.files.wordpress.com/2013/08/8-reactions-of-aqueous-solution1.pdf for explanation
Hi 🙂
Just wanted to say thank you for making these revision guides, got an A at AS because of them!
I am doing the CHEM5 redox equilibria chapter but I am confused as to why increasing the concentration of reactants would increase Ecell? (and vice versa). Can you help me with this?
Thanks in advance 🙂
It’s not an easy idea. If you have a reaction equation that has a positive Ecell then anything that will push the equilibrium (by application of le chatelier) to the products side would increase the Ecell further. Increasing concentration of reactants would push equilibrium to the product side to oppose the increase in concentration.
Hi, thanks for the notes, I have a few questions:
1) On module 4 guide 4, on pg 3, the bullet point where you say the functional groups take precedence over branched chains in giving the lowest number- what if there are multiple functional groups, which would give the lowest number? is it the same as the one that takes suffix form in the naming?
2) On pg 4 on the same guide, in the top right shouldn’t it just be oxo-propanoic acid (without the 2?); if the carbonyl were on the end it would be an aldehyde?
3) On pg 5 of the same guide, for acid anhydrides, does order matter if the alkyl groups are of different lengths? e.g. ethanoic butanoic anhydride vs butanoic ethanoic anhydride?
4) On module 4 guide 6 pg 2, for the 2nd molecule, does it matter whether you switch the numbers round to e.g. 4-chloro-1-methylbenzene, or is there a pattern we should follow for the exam?
5) On module 4 guide 8, in the acidity and bases section, the “species in neutral solution” looks to be a zwitterion? but in my other books, they say zwitterions exist at the isoelectric point, and the ph at which this occurs varies (e.g. for alanine it said it was ph=6); but neutral solution is always ph 7 under standard conditions? is this an inconsistency?
Thanks very much!
1) If there are multiple functional groups and branched chains then the highest priority functional group will take precedence over all others. Usually the C in a carboxylic acid being carbon number 1
2)It could just be oxo-propanoic acid yes
3) they get listed alphabetically
4)Don’t worry too much about numbering benzene rings. The highest priority side group should be number one (like above)
5) Yes it is a bit of an inconsistency. I think the exam board use the phrase neutral solution in this situation though. Neutral does not mean pH7 though. Water is not pH7 at temperatures other than 25C. Here it means [H+]= [OH-]
Are the Complex colours accurate for AQA? The CHEM5 Jan 2011 mark scheme says that the Chromium Hexaqua ion is Red/Ruby and your notes say blue. I know the Cr2+ ion is Blue but is it still blue with the water ligands?
Yes they are accurate. The question you refer to asks for the colour of Cr3+ and not Cr 2+. The accepted colours for aqueous Cr3+ are Ruby / red-blue / purple / violet / green
HI sir,
I think there might be 2 mistakes:
1)mod5-ch4) transition metals – pg 13 – (Cr(H20)6)3+ is a green sol not violet sol, and
2) mod 5 revision guide 2. periodicity – page 3 should be Mg(OH)2 is better than NaOH for treating acid in rivers and the stomach, not MgO is better than NaOH for treating acid in rivers and the stomach…
Thanks
The first is not a mistake. The Cr3+ ion ought to be violet but appears green because of an acidity reaction. Both colours would be accepted in the exam. The second is a mistake and I will change
Hi! i was wondering if you could help me with this question:
When solid potassium manganate (VII) is heated it decomposes according to the equation below
2KMNO4 —> K2MnO4 + MnO2 + O2
Explain, in terms of oxidation states, why this is a redox reaction.
Any help please??
You need to work out which element is being oxidised (Oxygen) and give the before and after oxidation numbers.
Then do the same for the element that is being reduced (Mn)- this one is slightly more complicated because there are two different Mn states in the products.
I thought the oxidation state of Oxygen is -2 and doesnt change?
It is -2 in compounds (except in peroxides). Here is turning into the element form O2. All elements in their element form have an oxidation number of zero
Mistake on mod 5 revision guide 2. periodicity – page 3 should be Mg(OH)2 is better than NaOH for treating acid in rivers and the stomach, not MgO is better than NaOH for treating acid in rivers and the stomach…