1. AQA Revision Guides

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 February 2021 )

1.3 revision guide Bonding(AS) (updated November 2018)

1.4 revision guide Energetics AQA(AS) (updated April 2020)

1.5 revision guide Reaction Kinetics (AS) (updated November 2018)

1.6 revision guide Equilibria (AS) (updated November 2018)

1.7 revision guide Redox(AS) (updated November 2018)

1.8 revision guide Thermodynamics AQA (updated February 2021 )

1.9 revision guide Rate Equations AQA (updated December 2019)

1.10 revision guide Equilibrium Constant Kp (updated November 2018)

1.11 revision guide Electrode Potentials AQA (updated December 2019 )

1.12 revision guide acid base equilibria AQA (updated February 2021 )

Inorganic Chemistry

2.1 revision guide periodicity (AS)(updated December 2019)

2.2 revision guide Group 2(AS) (updated November 2018)

2.3 revision guide Halogens AQA(AS) (updated April 2020)

2.4 revision guide Period 3 (updated December 2019)

2.5 revision guide Transition metals AQA(updated December 2019)

2.6 revision guide Reactions of Aqueous Ions AQA (updated February 2021 )

Organic Chemistry

3.1 revision guide introduction organic AQA(AS) (updated February 2021 )

3.2 revision guide Alkanes AQA (AS) (updated April 2020)

3.3 revision guide Halogenoalkanes AQA(AS)  (updated February 2021)

3.4 revision guide Alkenes (AS)  (updated November 2018)

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 (updated December 2019)

3.9 revision guide Carboxylic acids and derivatives AQA (updated February 2021)

3.10 revision guide Arene Chemistry AQA (updated February 2021)

3.11 revision guide Amines (updated November 2018)

3.12 revision guide polymers AQA (updated April 2020)

3.13 revision guide amino acids proteins and DNA (updated December 2019)

3.14 revision guide Organic Synthesis AQA (updated December 2019)

3.15 revision guide NMR (updated February 2021 )

3.16 revision guide chromatography(updated December 2019)

AQA mechanisms summary AS (AS)  (updated February 2021 )

AQA mechanisms A level summary  (updated February 2021 )

Practical Guide AQA (updated February 2021 )

463 thoughts on “1. AQA Revision Guides

  1. Ali

    Hi firstly I would like to thank you for these awesome notes and also I was wondering does entropy only apply to endothermic reactions?

    Reply
    1. chemrevise Post author

      entropy change happens with all reactions. It is of more importance with endothermic reactions because the only was delta G would be negative is if entropy change is positive.

      Reply
      1. Chemnesia

        Wouldn’t that only apply if the entropy change value was more positive than enthalpy change where temperature is positive?
        Why would a reaction where deltaH= -1034 and deltaS= +165 be feasible irrespective of temperature? If temperature is -6.3K or below then wouldn’t we get a positive delta G value?

  2. James

    Hi,

    Is it ok when drawing optical isomers to leave out the mirror line as long as they correctly drawn?

    Reply
  3. Akeel

    Hi, great site!

    I just wanted to ask in titration curves when you may be asked to draw a sketch for a curve or match it up. How do you know if the given acids and bases are strong or weak i.e. NH3.

    Reply
  4. Fudge

    Hi,one questions.

    On your acids and buffers equilibria it says adding a little acid shifts equlibrium of buffer to the left.

    But jan 12 q3e it says shifts to the right when a bit of acid is added?

    Reply
    1. chemrevise Post author

      That is because my notes refer to an acidic buffer solution where the equilibrium is HA –> H+ + A-
      Whereas the question on that paper refers to an alkaline buffer where the equilibrium is CH3CH2NH2 + H+ → CH3CH2NH3+
      As the H+ is on the different sides of the equilibrium in the two cases they will shift in opposite directions.

      Reply
  5. Irfah Parveen

    Thank you for all of your documents!

    One question about ozone layers..
    When a Cl free radical reacts with O3, why does it form a CLO free radical? Doesn’t taking an Oxygen away from the ozone, cause the “free radical-ness” of Chlorine to disappear? Why is it still a free Radical?

    Reply
    1. chemrevise Post author

      If you do a dot and cross diagram for ClO you will find it has an odd number of electrons which is what makes it a free radical. In this reaction the Cl is both a free radical as Cl and ClO

      Reply
  6. student321

    I have a problem with redox reaction, how do you work out redox half equations when the actual reactants and products are mentioned in the question. You have to construct two half equations then put them both into a full equation. Like it says potassium bromide reacts with sulphuric acid. When you write the half equation do you actually have to write the same number of moles or is it just one.
    Thank you.

    Reply
    1. chemrevise Post author

      I’m not sure I understand the question. In general if writing a half equation start with one mole of the reactant that is changing oxidation number and if necessary add H+ and H20 to balance any imbalance in O’s or H’s .

      Reply
      1. Nicky

        I am also having the same issue. In some questions, you are required to write just the ions with the number of electrons that reduced/oxidised it but in other questions you need to put in other molecules too. I can’t seem it work out when to do which of them. Thank you

      2. chemrevise Post author

        If there is an oxygen/ hydrogen in one of the reactants or products that is not balanced with the other substance then you need to use water and hydrogen ions to balance them. I explain how in redox revision guide

  7. Chemnesia

    Thank you so much for these notes! Great to use alongside the school textbooks when they’re not making sense.
    In regards to the redox equilibria notes in Unit 5:
    Say if we had an electrochemical cell where the half cells were zinc and copper, is Cu2+(aq) still being reduced to Cu(s) if the high resistance voltmeter is in place (as this would stop current flow)? I thought flow of electrons is prevented if there is no current…? But I’m quite uncertain with the concept of current.

    Reply
    1. chemrevise Post author

      If there is a high resistance voltmeter in place no current will flow and the reaction will not actually occur. Only if current is allowed to flow will the reaction start to occur

      Reply
      1. Chemnesia

        Thank you for getting back to me. Out of curiosity, if the reaction is not occurring, how does the voltmeter calculate the e.m.f value?

      2. chemrevise Post author

        This is physics really. A voltmeter across any cell will measure the maximum potential difference of the cell when no current flows. This maximum voltage is called the Electo Motive Force (EMF) of that cell. When current flows from the cell the potential difference drops and a smaller voltage is measured.

  8. student321

    I have another question. How to work out the chemical formula of an ionic and covalent compound. The halogens are diatomic but not in all compounds can you please tell me how to work out the formula of compounds and how to work out their oxidation states. A compound like Thallium Bromide seems covalent but actually is it? Thankyou.

    Reply
  9. student321

    You would have seen the Unit 1 Paper- Friday 23rd May. There were some unusual questions; how can we prepare for these surprise questions for the unit 2 exam- Next Tuesday. I was also wondering how to work out the shape TlBr3^2-. Please help me in this matter. Thanks.

    Reply
    1. chemrevise Post author

      Unusual questions are there to test whether people really understand the subject rather than having just remembered the answer to every past question. There is no short cut. You just need to learn the material really well and when you get an unusual question realising it must be an application of something you have learnt. Read the question and try to link it to a concept you have learnt. Don’t start making up science.

      For TlBr3 2- TL has 3 electrons in its outer shell. 3 Br’s add 3 more electrons. Add two more electrons because of the 2- charge This makes a total of 8 electrons made up of 3 bond pairs and 1 lone pairs. This makes it trigonal pyrimdial

      Reply
  10. Rootkix

    For unit 2 chemistry does the hess’s law method have to be known or can you do the method which one you prefer such as the formula

    Reply
    1. chemrevise Post author

      For AQA it is possible to use any method and go straight for the equations. You should be able to apply hess’s law cycles for unfamiliar examples though

      Reply
  11. Rootkix

    Chemistry was good today,this site has helped me with chemistry thanks for all the notes you have made here i appreciate it.i assume you have seen the paper for aqa chem 1,what did you think of it?

    Reply
    1. chemrevise Post author

      I’m glad you found the paper good. I thought it was a fair, well thought-out paper, very accessible to people who have done decent revision. There were some interesting new questions too.

      Reply
  12. J

    Hi,

    I wanted to ask you about covalent character in ionic bonding (thermodynamics). So in your revision notes it states that to get a tendacy towards covalent character in ionic substances it has to have: “positive ion is small, positive ion with multiple charges, negative ion is large and negative ion with multiple charges.” I got taught that: large negatively charged ion with less charge density and a small highly postively charged ion that gives the most covalent character because the postively charged metal cation polarieses the negative ion more strongly. Can you clarify this for me please and thank you.

    Reply
    1. chemrevise Post author

      The key feature is large charge and small size on the positive ion- these are polarising
      For the negative ion the most important factor is size. The bigger the ion the more easily it is polarised.
      The charge on the negative ion is often not mentioned at all in text books which suggests it is of less importance and it never features in questions. The charge density of negative ion would be complicated by the fact that when comparing ions a S2- ion would be bigger than a Cl- ion because it has the same number of electrons but one less proton.

      Reply
  13. student321

    I wanted to ask u about how to find the number of structural isomers of a specfic hydrocarbon like C6H14. Questions like this are mostly on alkanes. Exam tomorrow AQA Unit 1 2420. Please help me as quick as possible.
    Thankyou.

    Reply
  14. student321

    I need some quick help as the Unit 1 exam is tomorrow. Can you please tell me a quick way of finding all the possible structural isomers of a hydrocarbon. In the past exam q’s it has normally been alkanes. The question is just normally for one mark and there is no point taking a long time on a one mark question. Please help me as quick as possible.

    Reply
    1. chemrevise Post author

      The way I would do it is draw them out and count up. Do it systematically. Start straight chain, then remove a carbon and see where it can go as a side group. Then remove a second carbon and see where two side groups can go. If there is a functional group , see where you can put it on each of the chain isomers.

      Reply
  15. J

    Hi,
    So I am revising for the A2 exam and basically I was going over the sheet. So it said: “tertiary amines are stronger bases than secondary amines which are stronger than primary amines” (discussing base properties here). However when I was looking at the AQA Nelson Thorne book it said that tertiary amine was NOT stronger than the secondary amines because tertiary amines are less soluble in water. Can you clarify this for me please and thank you. (By the way, an amazing website :))

    Reply
    1. chemrevise Post author

      I am guilty of simplifying in the revision guides. The solubility point in the text book is correct but is not a point that has come up on the A-level. The inductive effect of the alkyl groups is counteracted by the lower solubility due to lower hydrogen bonding. The overall effect is that secondary and tertiary amines have roughly similar basic strength.

      Reply
  16. student321

    I wanted to ask about hydrate compounds. What does the dot in chemical formulas mean. Can you please explain to me how to find an unknown value in these hydrate compounds. Finally, can u please give me alink which explains this in detail.
    Thanks

    Reply
  17. student321

    I wanted to ask you about the alkanes section and the atomic structure section etc. in the AQA 2420 specification. Spec ref 3.1.6 and 1.1.1. It is necessary to know the history of the atom in the exama and it is necessary to learn the different fractions and products and temperatures of these various fractions in fractional distillation. One last thing is that how important is it to learn the How Science Works questions in the exam and how to prepare for these specific questions.

    Thanks

    Reply
    1. chemrevise Post author

      Learning the exact fractions and temperatures is no longer on the syllabus but you ought to be aware the sorts of fractions that come out near the top and near the bottom and general uses.
      There has never been a question about history of the atom. You ought to be aware that structures of the atom and electronic structures are models and chemists use various models.
      There aren’t really any questions one could label how science works, but there are lots that require people to think and apply knowledge- generally questions that start ‘suggest’. The deeper you learn the material, the easier those questions get.

      Reply
  18. student321

    Can you please post some topic based exam question on organic chemistry and naming organic compounds. Also, could you put up some on amount of substance. AQA 2420 AS Chemistry is the specification. Thanks

    Reply
    1. chemrevise Post author

      I won’t be posting any questions before the summer. I have plans to do this but it’s a long term task. Look at past papers on aqa website for the moment

      Reply
  19. Rootkix

    Do we have to know the whole process of fractional distillation? And for functional group isomers,will it always be cyclo,such as butene will be cyclobutane and can we just draw the shape instead of ch2 tp show bonds.cheers

    Reply
    1. chemrevise Post author

      You should be able to explain the basics of how fractional distillation works – connecting with ideas about intermolecular bonding.
      There are many different functional group isomers but in module 1 they are limited because we have not met many functional groups. The Alkenes/ cycloalkane pairing is very common.

      Reply
  20. student321

    I was just asking for some help. The unit 1 exam for AQA AS Chemistry is now around 12 days away. What advice can you give me.
    Thanks

    Reply
  21. Mimi

    Thnk you ever so mcuh for these notes! I really appreciate the hard work you have put in to making these notes. I can’t thank you enough. Again thank you, thank you, thank you ever so much!

    Reply
  22. pyro

    in the January 2011 chemistry unit 2 paper a question ask what reagent would be used to distinguish between mgcl2 and bacl2 is,i dont understand the answer.i know they are both in group 2 but it says any “soluble sulfate by name or formula e.g. sodium sulfate or
    sulfuric acid” or NAOH OR KOH. what is the link? cant find the answer from my aqa collins book

    Reply
    1. chemrevise Post author

      Many group 2 solubility questions focus on magnesium hydroxide being insoluble and/or barium sulphate being insoluble. If with a mixture of the two salts, adding sodium hydroxide would produce ppt of magnesium hydroxide with no change to barium salt . If sodium sulphate is added the barium salt will produce the ppt and magnesium salt no change.

      Reply
      1. nab

        But Mg(OH)2 and BaSO4 are both white percipitates, how is that distinguishing between the two? :S

      2. chemrevise Post author

        They wouldn’t be both white at the same time. If hydroxide ions are added only the magnesium would be a white ppt and the barium would show no visible change. Vice versa if sulphate ions are added.

  23. Frank

    in module 1 inside bonding,how did you work out the i3- ion and also i have had a problem like this before.in a past aqa paper there was a question to work out shape of cl3+ ion.how i was taught was if BCl3 then we do the number on the last atom which is 3 + the number of electrons in the outer shell of the first atom so it will be 3+3 and divide that by two to give a trigonal planar shape and plus before dividing if a negative ion or minus if positive but it does not work with those two

    Reply
    1. chemrevise Post author

      Your method works but you are misapplying it to examples where they are all the same atom. In I3- there is one central I attached to two others. The central one has 7 electrons and is attached to two others (so two electrons). That makes 7 +2 = 9. It has a minus charge so it becomes 10. Divide by two makes 5 pairs (2 bond pairs- 3 lone pairs).
      In Cl3+ there is similarly a central Cl with 7 electrons and is attached to two others (so two electrons). That makes 7 +2 = 9. Then it has a plus charge so is 8 electrons. Divide by two makes 4 pairs (2 bond pairs- 2 lone pairs).

      Reply
  24. jake

    i know these questions are only a mark or two but how do you balance big equations such as 3CuS(s) + ……HNO3(aq) ……CuSO4(aq) + ……NO(g) + ……H2O(I) im not sure where to start because so many things to balance an once i balance one element in a compound then another becomes unbalanced this is for as by the way

    Reply
  25. Tom

    Do you need to know all the electronegativities of all the elements in the periodic table? I was taught that if the difference is 0.5 or greater then it is dipole-dipole and if the difference is 0.4 or less it is van der waals. How do I know the electronegativity of the element in an exam without learning all of them?

    Reply
    1. chemrevise Post author

      You don’t need to learn the exact electronegativities of the elements. Just know the trends in the size across a period and down a group and where you would find the most electronegative elements. You should be aware the three most electronegative elements are F then O then N. Don’t worry about the exact numerical difference that brings about a change in bonding; They are only general guides. You may find electronegativities are supplied in a question. If they are not then it will only be a matter of talking about a large/small difference in electronegativities.

      Reply
  26. Chris

    these notes are the best ever! Ever since my teacher told my class about this site chemistry became clearer,notes are easy to read and understand and even some points on here are not mentioned in the aqa collins support book and if so there is no emphasis such as being bold.i wanted to ask is there any way of figuring out what compounds occur as such as mgcl2 because in unit 1 sometimes you get a question to write an equation which they say in words and finally what is the best way to revise for the empa (i have chemistry 3 via the x route) sorry for so many questions

    Reply
    1. chemrevise Post author

      Compounds that you are asked to write the formulae for like MgCl2 you should be able to work out from their positions in the periodic table and hence usual charge. It should be a matter of working them out and not remembering them. There are a few ions you should learn the charges for e.g. sulphate, carbonate, nitrate, ammonium and hydroxide ions.
      For EMPA revision I can only give general advice. Treat it like any module exam and revise as much as possible. I would look at the past EMPA’s and ISA’s on the AQA website and look for the sorts of questions they have asked in the past. I cover many of the points from past ones in the module 1 calculations, module 2 energetics, group 2, group 7, rates and alcohols topics

      Reply
  27. Rob

    hey again,is it necessary to leave ethane in the termination step as CH3CH3? will i be marked down for writing C2H6 Thanks

    Reply
  28. kris

    Hey,
    Could please show me how to solve this problem thanks. (been stuck on it for ages :s)
    Calculate the pH of a buffer which is 0.2 moldm^-3 with respect to ammonium sulphate and 0.1 moldm^-3 with respect to ammonia. (Ka of NH4+ = 5.6 x 10^-10 moldm-3

    Reply
    1. chemrevise Post author

      It’s an unusual question. Look at ka equation on acid base equilibrium. The ammonium salt is playing the role of the acid HA and the ammonia is it’s conjugate base A-. Put concentrations straight into equation

      Reply
  29. Charlie

    Hey Sir,
    For some of the equations state symbols are used and for others they are not. Do we need to simply remember for the exam which ones require state symbols or is there a specific way of telling? Thanks. Amazing notes by the way.

    Reply
    1. chemrevise Post author

      In general always include for precipitation reactions and energetics definitions like ionisation energy. The rest of the time they will say in the question whether to include them.

      Reply
  30. Alex

    I believe there is a mistake in mod 1 calculations example 2, the answer should be 0.0118 moles instead of 0.118 moles

    Reply
  31. chemrevise Post author

    The syllabus says “be able to describe the trends in atomic radius, first ionisation energy, melting and boiling points of the elements Na – Ar”. They used to include electronegativity and conductivity in the past. However you could still be asked about trends in electronegativity from the mention of it in the bonding part of the syllabus (see bonding revision guide). If you know the type bonding of the period 3 elements you ought to be able to work out the conductivity as well- I suppose it could come up as a “suggest” question.

    Reply
      1. chemrevise Post author

        I don’t think there is actually a clear correlation. In period 3 just think of the metals as conducting, Silicon semi conducting and then phosphorus to Argon as non-conducting.

  32. Matthew Smith

    Hi these are great notes!!, however in the organic synthesis routes pack, shouldn’t the test for primary and secondary alcohols along with aldehydes be potassium dichromate not sodium dichromate?

    Reply
    1. chemrevise Post author

      It is the dichromate ion that is reacting with the alcohol. It does not matter if it is combined with sodium or potassium as these are spectator ions. You can therefore use either sodium or potassium dichromate.

      Reply
  33. Lucy

    Found this from a link on TSR. Absolutely fantastic and helps so much! Concise yet detailed explanations are fab. Thank you! 🙂

    Reply
  34. efbeafs

    fantastic notes thank you.
    on page 2 on mod 4 revision guide 6. benzene the first example in the top left corner i think there is a mistake. (1,4-dimethylbenzene) shouldn’t it be 1,3-dimethylbenzene?

    Reply
  35. Arif Ahmed

    Its the best note ever I have seen, but do you know any other sites for similar type of notes on A Level Physics & Biology?

    Reply

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