AQA CHEM2 ~ May 23rd 2012 ~ AS Chemistry

PERFECT! Exactly what I was looking for, thank you!

Lol thats pretty funny

revision just not fun anymore, its just consisting of going through content, past papers etc lol Just wanna do thrm nowww I wont be saying that when the exam is in a week lol

its horrible I wish they'd appreciate how important the work actually was and at least give us a qualified teacher ¬_¬


Thankyou good to see where same ish in terms of progress...totally agree about past papers .

Yea that was the case for me - so many silly errors

Revision was never fun in the first place?! Sigh, it feels like there are so many more mechanisms and content based things that I still need to learn I'm worried as my first exam is in ~2 weeks now! I'm no way ready



I'm sure we'll be able to finish the course, hoping to finish the course this weekend as we'll have the bank holiday weekend which is always good Hopefully past papers starting tuesday then

I got "Part 1" of my mock back, which were Q1-5 (or 6) as the mock was split into 2 sessions. And got 46/51 which is good But I'm dreading Part 2, as I know I lost loads of marks there

Hmm...do you two/anyone else have definitions for enthalpy change of formation/enthalpy change of combustion or Le Chateliers principle? I just want a crisp definition as I ended up getting 1/3 for enthalpy of combustion

enthalpy change of formation: the enthalpy change when one mole of a compound is formed from it's constituent elements. Under standard conditions and in their standard states? pretty sure that's 3 marks?

Hmm...do you two/anyone else have definitions for enthalpy change of formation/enthalpy change of combustion or Le Chateliers principle? I just want a crisp definition as I ended up getting 1/3 for enthalpy of combustion

Do you need the standard conditions bit? As I thought it was just enthalpy change when one mole of a compound is formed from its elements in their standard states? I know they're similar, but wasn't sure if I would get 2 or 3 for that...

The standard molar enthalpy of combustion is the total enthalpy change when one mole of substance is completely burned in oxygen under standard conditions, all reactants and product in their standard states.

You can tweak that definition to get the definition for formation.

Le Chatelier's principle states that if a system in equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance.

You can tweak that slightly and use words like oppose and so on.

Indeed, you do need to mention standard conditions to get the 3rd mark.

Hmm...do you two/anyone else have definitions for enthalpy change of formation/enthalpy change of combustion or Le Chateliers principle? I just want a crisp definition as I ended up getting 1/3 for enthalpy of combustion

Thanks a lot So Enthalpy of formation is the enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions? - Doesn't saying the standard states bit get the mark for standard conditions? As standard state is achieved by standard conditions?

I went through each paper and found the 'definition' questions and the MARK SCHEME answers.

1. State what is meant by the term activation energy. (2)

- The activation energy is the minimum/least/lowest;
- Energy for a reaction to occur/to go/to start OR
- Energy for a successful/effective collision

2. State what is meant by the term rate of reaction. (1)

- (Measured) change in concentration (of a substance) in unit time/given time

3. State what is meant by the term standard enthalpy of formation. (3)

- M1 The Enthalpy change/heat change at constant pressure when 1 mol of a compound/substance/product
- M2 is formed from its (constituent) elements
- M3 with all reactants and products/all substances in standard states

4. State what is meant by the term catalyst. (1)

- A substance that speeds up/alters the rate but is unchanged at the end/not used up.

5. State what is meant by the term carbon neutral. (1)

- An activity which has no net/overall (annual) carbon/greenhouse gas emissions to the atmosphere OR
- There is no change to the total amount of carbon dioxide/carbon/greenhouse gas present in the atmosphere.

6. State the meaning of the term hydrolysis. (1)

- Splitting/breaking the C-X/bond(s) using/by (adding)/with water OR
- Splitting/breaking the molecule/substance/compound using/by (adding)/with water.

7. State the meaning of the term nucleophile. (1)

- An electron pair donor OR
- Forms a covalent or co-ordinate or dative bond by donating a pair of electrons

8. State the meaning of the term molecular ion. (1)

The molecular ion is:
- The molecule with one/an electron knocked off/lost OR
- The molecule with a (single) positive charge OR
- the ion with/it has the largest/highest/biggest m/z (value/ratio) OR
- the ion with/it has an m/z equal to the Mr

9. State the meaning of the term enthalpy change. (1)

- Heat (energy) change at constant pressure

10. State Hess's Law. (1)

- The enthalpy change/heat (energy) change (at constant pressure) in a reaction is independent of the route/path taken (and depends only on the initial and final states)

11. State what is meant by the term unsaturated as applied to an alkene. (1)

- Contains a C=C OR a double bond

12. State what is meant by the term stereoisomers. (2)

- M1 Compounds with the same structural formula
- M2 with atoms/bonds/groups arranged differently in space OR
- atoms/bonds/groups have different spatial arrangements/different orientation.

13. State Le Chatelier’s principle. (1)

- (If any factor is changed which affects an equilibrium), the position of equilibrium
will shift/move/change/respond/act so as to oppose the change. OR
- (When a system/reaction in equilibrium is disturbed), the equilibrium shifts/moves in a direction which tends to reduce the disturbance

14. Give the meaning of the term standard enthalpy of combustion. (3)

- M1 The enthalpy change (or heat change at constant pressure) when 1 mol of a compound/substance /alcohol
- M2 is burned completly/in excess of oxygen
- M3 with all reactants and products/all substances in standard states
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I think I am missing a few but I'll add them on as i find them or feel free to add definitions.

Does anyone know the equations you need to know for the reactions of the Group 7 elements with Sulphuric acid and water???

Reactions with H2SO4:

NaCl(s) + H2SO4(l) --> NaHSO4(s) + HCl(g)

NaBr(s) + H2SO4(l) --> NaHSO4(s) + HBr(g)

NaI(s) + H2SO4(l) --> NaHSO4(s) + HI(g)

Reaction with H2O:

Cl2(g) + H2O(l) <--> HClO(aq) + HCl(aq)

In the presence of sunlight, this reaction occurs:

2Cl2(g) + 2H2O(l) --> 4HCl(aq) + O2(g)

Obviously, you can work out what would occur should you react the others with water and in the presence of sunlight.

It's useful to know this reaction with alkali as well:

Cl2(g) + 2NaOH(aq) --> NaClO(aq) + NaCl(aq) + H2O(l)

you forgot discussion of grade boundaries the day they're released
pre results panic
post result congrats/condolences

I know Well done on your mock result (sorry for the late reply, I've been so busy with work, and realising how little time we have left...) Ah, you seem to be at a similar place to me then, as I've just done extraction of metals, but I realise how behind I am on other subjects. Hopefully by the end of this week (well including the bank holiday in the week ) I should be all revised for most my subjects. And so I can start past papers

I think it's just a waste of the past paper if you do it without knowing what you're doing...

I still haven't got my chemistry back...it's always the chemistry teachers that are the slowest at marking I can imagine that I just lost marks everywhere, but not necessarily concentrated in one section.



Thanks a lot! So is it important to not just look at the wave number but also the transmittance? As I think in the mock I just looked at the wave numbers and found it quite confusing. Is there much else that we need for this section?



Ah :/ I'm always the one that overwrites...it just makes me feel better that my revision actually did something, so if it's a knowledge based question (mainly in biology), I'd go made on the "explain how x occurs" questions Ah, the invigilators at our school give out 1 sheet each time as well, but one got annoyed at the RE GCSE exam, so just gave me 3/4 sheets the third time I asked

How's your revision going?

Hi I have a question. In unit 1 there is normally a question which is "name the element with these successive ionisation energys".. Does anybody know an easy way to learn them because i always think they are so random lol :L Thanks everyone and good luck!!

Sure - look for the biggest jump in successive IEs - the group number is the same as the last no IE before the gap eg for Aluminium (Gp 3) there is a huge gap between IE3 and IE4. This big jump shows the next electron to be lost is in an inner shell.

If they are unkind and do not tell you which period it is in then often you can know just by the number of successive IEs.
eg say you know it's period 2 or 3, but not which, and they list say six successive IEs and there's a big jump between IE1 and IE2 - it must be in Group 1, and must be Na not Li as Li only has 3 electrons so couldn't have ten successive IEs.