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AQA GCSE Chemistry - C2 & C3 (14th May 2015)

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Original post by pollyy
Oh, which revision guide is that? Mine could be wrong!

Lonsdale Revision Plus. It's not a typo either, there's a little diagram with a pile of impurities gathering below the cathode.
Original post by RotomGuy
Alright, but why would the object being plated top the solution up with more silver ions if it needs to be plated with it?


This is because the electrolyte containing silver ions may eventually all have moved to the negative electrode. However this may not be enough to completely plate the object. So more Silver ions are added so that the object is coated with a large enough layer/amount of the metal
(edited 8 years ago)
Original post by Workangel_24
Polymers have not come up on the 2014 paper so it could come up tomorrow.

Here's some predictions for 6 markers:
Exothermic and Endothermic?
Rates of Reactions
Soluble and Insoluble salts
Ionic substances
Thermosetting and Thermosoftening polymers
Electroplating
Collision theory - probably 3/4 marker
Metallic bonding
Factors that affect the yield of reactions

I think it will be about the comparison of thermosoftening and thermosetting polymers
Original post by mediaya
Could any one explain me how to do he empirical formula? Am really strugling with this������


For emperic formula you will get a percentage to start with eg 80% of a hydrocarbon is carbon and 20% is hydrogen.
To find the emperical formula you need to work in grams so if they haven't given you a mass already just use 100 so
80% of a 100 = 80g so 80g is carbon and 20%= 20g so 20g is hydrogen
You then need to divide that mass by the actual Ar of the atoms so carbon=12 and hydrogen=1(they are found in periodic table) so then divide the actual mass by the Ar to find the moles so
80/12= 6.67
20/1=20
To find the emperical formula see which has the smallest mole and use that as the 1 (in this case carbon as 6.67 is smaller than 20)
So carbon= 1 and hydrogen= 20/6.67
So hydrogen= 2.9 we need a whole number so round to 3
So our formula is 1 carbon and 3 hydrogen so CH3 (the 3 needs to be little ofcourse)

Hope this helped it's hard to explain sometimes
(edited 8 years ago)
Original post by neil20143
The Haber Process is Unit 3, not Unit 2 :smile:


Oh thank God for that! I just sat looking at the screen with tears welling up...
Reply 245
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Original post by maxjackson5
Thermosoftening polymers are used for plastic containers and they can be recycled because they can be melted and re-moulded. This is because there are weak intermolecular forces, and there is no covalent bonds between the layers.
Thermosetting polymers are used for materials that need to be resistant, i.e a frying pan handle. Once they have been set, thermosetting polymers can't be re-moulded because they have strong covalent bonds between the layers.



Actually just saved my life here, thanks!!! Anyone got standard 6 points for a Q on soluble and insoluble salts? Thank you!!!:smile:

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[INDENT]can someone help me with electrolysis... just a simple method please x[/INDENT]

Does anyone else feel like crying or is that just me?
Original post by whatgeorgiedid
Does anyone else feel like crying or is that just me?


i do :frown:
Original post by whatgeorgiedid
Does anyone else feel like crying or is that just me?


Nah me too dw :'l
Reply 250
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Original post by whatgeorgiedid
Does anyone else feel like crying or is that just me?


I do :frown: Dead scared!
Original post by liv1111
i do :frown:


The emotions are so real right now - I'm a history and English literature kinda gal and this is just not good for me at all!
Original post by whatgeorgiedid
The emotions are so real right now - I'm a history and English literature kinda gal and this is just not good for me at all!


i actually like science, but i've had a **** teacher and now i've left it a bit late to actually learn anything lol
Original post by neil20143
I do :frown: Dead scared!


oh thank god for that! let's comfort each other in the fact that we probably know what endothermic and exothermic reactions are... just about anyway.
Original post by mediaya
Could any one explain me how to do he empirical formula? Am really strugling with this������


1. You will be given 2 (possibly 3) elements
e.g Sodium (Na) and Sulphur (S) and Oxygen (O)

2. You will be given the mass or the percentage - they both work the same way
e.g 4.6g of Na and 3.2g of S and 6.4g of O

3. You need to get the Mr of each element by looking at the top number on the periodic table.
In this case Na is 23 and S is 33 and O is 16

4. Divide the percentage or mass of each by its own Mr value
4.6/23 = 0.2 and 3.2/33 = 0.1 and 6.4/16 = 0.4

5. Divide this result by the lowest result just obtained.
So the lowest result was 0.1 - So all 3 are divided by 0.1
0.2/0.1 = 2 and 0.1/0.1 = 1 and 0.4/0.1 = 4

6. Put these 3 values in front of the symbols
Na2 S1 O4
= Na2SO4
This is the final answer
(edited 8 years ago)

1.

Original post by liv1111
i actually like science, but i've had a **** teacher and now i've left it a bit late to actually learn anything lol




oh my gosh, you poor thing! best of luck with tomorrow - I'm sure everything will go swimmingly *fingers crossed, touch wood*
Can someone help with an ideal list of points for a 6 mark question on LD, HD, thermosetting/softening polymers? I can't recall what the first two are and I can't think how to write 6 marks worth of polymer structure.
Original post by whatgeorgiedid


oh my gosh, you poor thing! best of luck with tomorrow - I'm sure everything will go swimmingly *fingers crossed, touch wood*


aww thank you! just praying that the grade boundaries are low :tongue: all the best for you too!
Original post by Louisbirch
Has anyone got any good tips/acronyms/ways of remembering the ion tests?


this sounds pretty immature but the way I remember flame test colours is "little cock sods yell penis loudly caressing rainbow balls gently"
(Lithium crimson, sodium yellow, potassium lilac, calcium red, barium green)
Original post by liv1111

•

[INDENT]can someone help me with electrolysis... just a simple method please x[/INDENT]



*Electrolysis separates ionic compounds using electricity*

The circuit is comprised of a battery, two electrodes and the electrolyte (basically a beaker with the compound you want to separate in)

Positive metal ions are attracted to the negative anode. They gain electrons to form metal atoms. This is called REDUCTION.

Negatively charged ions are attracted to the positive anode where they lose electrons, often producing oxygen bubbles. This is called OXIDATION.

I'd say the basic key points to remember are:
- Ionic compound MUST be molten or in a solution for electrolysis to work
- metals ions -> negative electrode
- non metals -> positive electrode
- OIL RIG is a great memory tool (Oxidation Is Loss (of electrons) Reduction Is Gain (of electrons))

I think that just about covers the basics, hope that helps!
There are some good videos on YouTube if seeing something visual will help. Most of them are condensed into 8-10 minute lessons.

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