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AQA - Unit 5 - Energetics, Redox and Inorganic Chemistry watch

1. (Original post by me7)
Not sure if this has been asked before but can't seem to find it! I am VERY stuck on the January 2010 paper. Question 8C. If anyone could help it would be very appreciated!!!!! I dont understand how we are meant to know all the equations? Do we just need to memorize them??

http://store.aqa.org.uk/qual/gce/pdf...W-QP-JAN10.PDF
Well this is a tough one but we do actually know the equations if you think about the question logically (took me foreverrrrr :P)

Basically we know that H3PO4 is an acid so it will react with a base making a salt and water. We are told that it reacts with the NaOH which is a base

So.......H3PO4 + NaOH......? something (salt) + water?

You know that to make the water the 3 H's need to be removed from the H3PO4 (because it is the proton donor) And this will leave PO4 (3-) there for you need 3 Na(+) bonding with the PO4 to make 3NaPO4....now left with OH and 3 H's which combine to make water!

Piece it all together and balance the equation:

H3PO4 + 3NaOH ---> 3NaPO4 + 3H2O

Hope that helps!!
2. (Original post by ncollier4)
Well this is a tough one but we do actually know the equations if you think about the question logically (took me foreverrrrr :P)

Basically we know that H3PO4 is an acid so it will react with a base making a salt and water. We are told that it reacts with the NaOH which is a base

So.......H3PO4 + NaOH......? something (salt) + water?

You know that to make the water the 3 H's need to be removed from the H3PO4 (because it is the proton donor) And this will leave PO4 (3-) there for you need 3 Na(+) bonding with the PO4 to make 3NaPO4....now left with OH and 3 H's which combine to make water!

Piece it all together and balance the equation:

H3PO4 + 3NaOH ---> 3NaPO4 + 3H2O

Hope that helps!!
Thank you so much!! That was very helpful. It seems so simple when you say it like that Not looking forward to this exam
3. (Original post by me7)
Thank you so much!! That was very helpful. It seems so simple when you say it like that Not looking forward to this exam
No problem

Yeah at first I thought we had to memorise random equations like that, was so confused how everyone spouted them out

But then someone told me how to work it out and I was like OHHHHHHHHHHH that makes life easier, felt I owed someone else it too ;]
because unfortunately AQA are mean and like to make us work for our marks

Same same, especially if we get a question like the one you posted, its a horrible question

GOOD LUCK EVERYONEEEEE! Lets all hope our memories do us justice and we can remember all the colours and equations
4. (Original post by ncollier4)
Piece it all together and balance the equation:

H3PO4 + 3NaOH ---> 3NaPO4 + 3H2O

Hope that helps!!
Should be:
H3PO4 + 3NaOH ----> Na3PO4 +3H20
5. (Original post by ncollier4)
OH and also.....the reactions concerning the production of methanol with the C2O3 catalyst?! I cant find the information anywhere
That's just simply: 2H2 + CO -> CH3OH.
You use C2O3 with zinc/ copper (II) oxides.
6. (Original post by Y.D)
anyone else envisaging a nightmare paper after hearing the horror stories of CHEM4 and the OCR paper today?
yes. sat chem4, and it was torture
7. (Original post by ncollier4)
OH and also.....the reactions concerning the production of methanol with the C2O3 catalyst?! I cant find the information anywhere
Equations are -

CH4 + H2O ---> CO + 3H2

CO + 2H2 ---> CH3OH

All in the gaseous state.
8. Does anybody know what synoptic stuff we have to learn???
9. hey can someone explain to me how to do born haber cycles. i understand the definitions but i always get the wrong answer. inorder to get the answer it takes me a long time constructing the cycle which is very time consuming for a 3 mark question. does anyone know how to do it without a cycle, if yes can someone explain how you would do it.

thank you
10. (Original post by l4ith)
Do we need to know AS metal extraction?
I learnt the reactions anyway - takes like 20 mins max. It does say in a 'link' - make sure you know the principles of metal extraction. Tbh, all this synoptic stuff is annoying cause its ambiguous as to what could come up.
11. (Original post by Sheldon)
Should be:
H3PO4 + 3NaOH ----> Na3PO4 +3H20
OOOOOOOOOPS!!! Paha I thought when i sent it bet ive done something stupid here :P

Thanks for the correction! I cant balance simple things how will i survive this exam....... I blame revision for mushing up my brain!
12. (Original post by azaking)
Equations are -

CH4 + H2O ---> CO + 3H2

CO + 2H2 ---> CH3OH

All in the gaseous state.
Thank youuuuuuuuuuuuuuuuuuuuuuu

But where does the catalyst come in?
13. (Original post by Mazii)
That's just simply: 2H2 + CO -> CH3OH.
You use C2O3 with zinc/ copper (II) oxides.
Do we need to know how the catalyst works with the reactants or do we just need to know that thats the catalyst?

Merciiii
14. (Original post by ncollier4)
Do we need to know how the catalyst works with the reactants or do we just need to know that thats the catalyst?

Merciiii
I reckon yu proberbly just need to know that it catalyses the reaction
15. what should i do ta tackle the synoptic element of the paper
16. (Original post by kabolin)
what should i do ta tackle the synoptic element of the paper
Have a look at some past papers, that'l give you an idea of how much of the exam is likely to be synoptic...

what i'm doing is going over all trends of the periodic table and and some reagant stuff
17. Can anyone help with the mathsy stuff of born haber cycles?
18. how do you find the mole ratio in this equation,

2VO2+8H+ + 3Zn----->2V2+ + 4H2O + 3 Zn+
19. Do we need to know all the little details about electrochemical cells? Pleeeeeease say no!
20. In the specification it says that we need to be able to define enthalpy of atomisation of an element and of a compound. I have never come across one for a compound :/ Does anyone have any ideas of how this would be defined or have an example of an equation where this is the case?

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