AQA Chemistry C2 [Pre Exam Discussion]*

Original post by LimeTree.

Oh thank god! xD

I literally almost died :')

Good luck guys!

Thank you and good luck also :smile:

Reply 42

OP

My predictions:
Questions:

- Draw electronic structure
- RFM
- Percentage Yield
- HSW questions
- Covalent Bonding Features + Graphite
- How does Graphite conduct electricity
- Nano Technology questions
- Intermolecular Forces
- Salts + Filtration
- Atom Economy + Questions on that
- Finish it off Empirical Formula!

Now if that does come up im a Genius! :P Agreed! lol :smile:

Reply 43

FFX91

Original post by ruby :)

im not too stressed yet.. it will hit me sunday night but im confident after biology!

one past paper question confused me to do with empirical formula, ill post it here and see if any of you can explain it :smile:

When 0.4g of a hydrocarbon gas was completely burnt, 1.1g carbon dioxide and 0.9g water were the only products. Calculate the number of moles of co2, and water produced, and use this to calculate the empirical formula of the original hydrocarbon.

so i worked it through like a normal question and got a ratio of 1 mole co2: 2 moles h2o, but then didnt know how to find the empirical formula of the original hydrocarbon?
please help :0

Urmmm are you sure this is additional science, seems a bit complicated? Never seen it before either, and surely you'd get like 0.1 moles of carbon or something stupid? Dont know how it'd help you find the empirical formula either?

Reply 44

FFX91

Does anyone have a good, simple resource on salts, filtration, evaporation and precipitation + the acid + alkali stuff? Thats the gap in my C2 knowledge atm. :smile:

Reply 45

lonsdale123

is this your real gcse exam or school mock or what??

why do you have the additional science exam in january?

Reply 46

EllHv1

1

Hi TSR,

This is my first post, and I have been following these pre exam discussion threads for some time, they're really useful!

I have a query about the chemistry. Is it just me or do you all also find that there's never much about acids and bases reactions in the past papers? For me, this chapter of the unit is a real grey area, I'm not terribly sure about all the different reactions the textbook mentions, producing certain salts etc...but these topics never really turn up anyway, so I've been ok. (Apart from the odd 'filtration', or 'OH- = alkali' question...)

So is it possible that they might focus more on this topic area? Also, if anyone would care to go over and explain the stuff about the different reactions and salts and solubility I'd be really grateful!

Thanks :biggrin:

Reply 47

Aaaaah! It's tommorow, my main problem (I discovered this in B2), is timing, if I had another fifteen minutes i'd be fine... but no :frown:

Reply 48

Original post by lonsdale123

is this your real gcse exam or school mock or what??

why do you have the additional science exam in january?

We have B1, C1, P1 at the end of year ten, B2, C2, P2 in January year 11 and B3, C3, P3 at the end of year 11 :smile:

Reply 49

king101

3

Original post by EllHv1

Hi TSR,

This is my first post, and I have been following these pre exam discussion threads for some time, they're really useful!

I have a query about the chemistry. Is it just me or do you all also find that there's never much about acids and bases reactions in the past papers? For me, this chapter of the unit is a real grey area, I'm not terribly sure about all the different reactions the textbook mentions, producing certain salts etc...but these topics never really turn up anyway, so I've been ok. (Apart from the odd 'filtration', or 'OH- = alkali' question...)

So is it possible that they might focus more on this topic area? Also, if anyone would care to go over and explain the stuff about the different reactions and salts and solubility I'd be really grateful!

Thanks :biggrin:

THEY GIVE YOU THE INFORMATION IN A TABLE SUCH AS IN THE JAN AND JUNE PAPER, OF WHAT IS SOLUABLE AND INSOLUABLE ETC. YOU DONT NEED TO REVISE BY MEMORY WHAT IT IS. Dont Worry, you will be fine! :biggrin:

Reply 50

Raafae

1) Why is graphite useful as a conductor?
In graphite, each carbon atom is covalently bonded to three other carbon atoms, this allows one electron from each atom to be delocalised.
The delocalised electrons can carry current.
[No need to include anything about layers here max is 3 marks probs]
2) Why is graphite useful in pencils (very unlikely)?
In graphite, each carbon atom is covalently bonded to three other carbon atoms, this allows one electron from each atom to be delocalised.
The carbon atoms form layers and the electrons hold the layers together.
However, the force of attraction between the layers is weak, therefore the layers can slide off easily.

Reply 51

king101

3

Original post by TheFootyKing19

My predictions:
Questions:

- Draw electronic structure
- RFM
- Percentage Yield
- HSW questions
- Covalent Bonding Features + Graphite
- How does Graphite conduct electricity
- Nano Technology questions
- Intermolecular Forces
- Salts + Filtration
- Atom Economy + Questions on that
- Finish it off Empirical Formula!

Now if that does come up im a Genius! :P Agreed! lol :smile:

- Draw electronic structure= each shell can hold up to [2,8,8]
- RFM=All AR added up, in other way 'mass number' added up
- Percentage Yield=Actual/What you could have got
- HSW questions=Stuiped Questions
- Covalent Bonding Features + Graphite=Simple
- How does Graphite conduct electricity=Delocalised electrons etc.. per layer
- Nano Technology questions=0.o im unsure about this chapter
- Intermolecular Forces=Simple molecular, ionic etc..
- Salts + Filtration=This chapter just is boring and confusing.
- Atom Economy + Questions on thaT=Easy
- Finish it off Empirical Formula!Easy

Reply 52

Can someone explain empirical formula (working it out)
confuzzled!!

Reply 53

OP

Atom Economy - Empirical Formula - Percentage Yield will come up tomorrow imo

along with structure and bonding in metals/graphite/sand/diamond

Reply 54

Original post by TheFootyKing19

Atom Economy - Empirical Formula - Percentage Yield will come up tomorrow imo

along with structure and bonding in metals/graphite/sand/diamond

Thats all the annoying stuff :frown:

Reply 55

AmyLH

Morning, well Afternoon all :biggrin:

Reply 56

OP

Original post by Jesss9

Can someone explain empirical formula (working it out)
confuzzled!!

Calculate the empirical formula of a compound composed of 38.67 % C, 16.22 % H, and 45.11 %N.

38.67 g C x 1mol C = 3.220 mole C
16.22 g H x 1mol H = 16.09 mole H
45.11 g N x 1mol N = 3.219 mole N

C =3.22 H =16.09 N =3.219

If we divide all of these by the smallest one It will give us the empirical formula

C1H5N1 is the empirical formula or CH5N

Basically:
1: divide percentage by the Ar.
2: Then with that divide it by the lowest
3: Get the ratios
4. Done

Reply 57

EllHv1

1

Original post by king101

THEY GIVE YOU THE INFORMATION IN A TABLE SUCH AS IN THE JAN AND JUNE PAPER, OF WHAT IS SOLUABLE AND INSOLUABLE ETC. YOU DONT NEED TO REVISE BY MEMORY WHAT IT IS. Dont Worry, you will be fine! :biggrin:

Ahh, I see. Looking in my June 10 November mock and we were given solubility tables. Reassuring to know we definitely don't need to know all that :smile:

Thanks

That last chapter is really confusing, everything else isn't too bad though. :smile:

Reply 58

Original post by TheFootyKing19

Calculate the empirical formula of a compound composed of 38.67 % C, 16.22 % H, and 45.11 %N.

38.67 g C x 1mol C = 3.220 mole C
16.22 g H x 1mol H = 16.09 mole H
45.11 g N x 1mol N = 3.219 mole N

C =3.22 H =16.09 N =3.219

If we divide all of these by the smallest one It will give us the empirical formula

C1H5N1 is the empirical formula or CH5N

Basically:
1: divide percentage by the Ar.
2: Then with that divide it by the lowest
3: Get the ratios
4. Done

Thanks

Reply 59

OP