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

1. (Original post by zc555)
Also, I'm struggling with Unit 3 Titration Calculations. Can anyone help? Thanks (the previous comment was for unit 3 too)
Step 1: work out the number of moles in the burette (this will be the substance which you know both the volume AND concentration of) moles = vol x conc (remember, you will be given a volume value in cm3 but you need to use it in dm3, so just divide by 1000)

Step 2: work out the number of moles in the flask - this is done by working out the ratio of each substance for example CH3COOH + NaOH you have 1:1 ratio, but if it was CH3COOH + 2NaOH the ratio would be 1:2. Depending on the ratio, use the moles from the burette to work it out. So, if the ratio is 1:1 the moles will be exactly the same. If it's 1:2 the moles in flask will be double the moles in the burette.

Step 3: work out the concentration of the substance: conc = vol / moles

Sorry if this is confusing, tell me if you need more help.
2. Has some got mygcsescience account that I can use it to Watch the videos for c2 and c3 please?
3. (Original post by maxjackson5)
you mean fortunately! I'm not too keen on it personally ahah, thanks though
I'm not keen either! I hope Empirical formula comes up!
4. (Original post by neil20143)
I'm not keen either! I hope Empirical formula comes up!
hahaa me too! It's actually much easier than people think and you can get a lot of fast marks if you get it correct
5. (Original post by mediaya)
Yes the polymer question could come up cause that has not been on for a while. I would be so happy if that comes up but i dont think so cause it s too easy. It could come up as a 4 marker maybe
whats the polymer question???

this is c2 right..
6. (Original post by maxjackson5)
yeah something along those lines haha, I'm sure you'll do fine!
There's not much 6 markers they can give tbh.. Can't think of much.

Paha.. No. I did dreadful in the Biology exam and weirdly I find biology much easier than chemistry, so I don't have high hopes for Chemistry.
7. (Original post by neil20143)
I made a prediction list of what I think will come in C2 if it'll help!:
-Diamond & Graphite
-Nanoparticles
-Thermosetting & Thermosoftening polymers
-Catalysts
-Salts
-Empirical Formula (hasn't come up very recently so it's very likely)
-Simple Molecules (Why is Carbon Dioxide a gas at room temperature or something like this)

Is that the salts and electrolysis questions? For this I made a little mind map, colour coded each section so that I could differentiate each bit! That helped me understand what links with what. Then I just had to memorize it If that's your main problem
I think that electrolysis, polymers and nanoparticles ALL came up on the 2014 paper I did, surely it wont come up again???
8. (Original post by Samistrawberry)
There's not much 6 markers they can give tbh.. Can't think of much. Paha.. No. I did dreadful in the Biology exam and weirdly I find biology much easier than chemistry, so I don't have high hopes for Chemistry.
I am sure you will be fine, cuz this time biology was pretty challenging
9. !
10. (Original post by fabsafxo)
I think that electrolysis, polymers and nanoparticles ALL came up on the 2014 paper I did, surely it wont come up again???
None of them did except for electrolysis :P Nanotubes were asked but they were a completely different concept (more graphite-style question) and polymers never came up. Electrolysis also includes electroplating and brine electrolysis, both which have not come up in the new papers yet.
11. (Original post by Samistrawberry)
There's not much 6 markers they can give tbh.. Can't think of much.

Paha.. No. I did dreadful in the Biology exam and weirdly I find biology much easier than chemistry, so I don't have high hopes for Chemistry.
what 6 markers do you see coming up??
I find chemistry a lot easier, I just CANT LEARN biology........

I mean theres only the one I can think of for 6 markers which is the kinetic energy in particles....
12. (Original post by amber.991)
Step 1: work out the number of moles in the burette (this will be the substance which you know both the volume AND concentration of) moles = vol x conc (remember, you will be given a volume value in cm3 but you need to use it in dm3, so just divide by 1000)

Step 2: work out the number of moles in the flask - this is done by working out the ratio of each substance for example CH3COOH + NaOH you have 1:1 ratio, but if it was CH3COOH + 2NaOH the ratio would be 1:2. Depending on the ratio, use the moles from the burette to work it out. So, if the ratio is 1:1 the moles will be exactly the same. If it's 1:2 the moles in flask will be double the moles in the burette.

Step 3: work out the concentration of the substance: conc = vol / moles

Sorry if this is confusing, tell me if you need more help.
You make it sound so straight forward! Thank you so much! I'll have a go practising this now.
13. (Original post by zc555)
You make it sound so straight forward! Thank you so much! I'll have a go practising this now.
Great! No problem, please tell me if you struggle with anything because I'd hate to be the cause of lost marks :/ (that being anything to do with titrations, I can't say I'm able to teach the whole unit )
14. (Original post by Jules12345)
what do we think for six marker on c2?????
I think:

1. Comparing fullerenes
2. How to do each chromatography
3. The rate of reactions experiments
4. Collision theory
5. Making salts
6. Electrolysis
15. Hi, can someone go through comparing energy released by fuels, Energy transfers in solutions both using Q = mCT and Calculating Bond Energies formula for Unit 3 please? I seem to be having huge problems with maths in Chemistry, I'll be very grateful for your help!
16. (Original post by siobhanjerry)
any key points on electrolysis because it seems soo lengthy
Elctrolysis is the breaking down of ionic cooounde using electricity. It therefore only works if the substance is in a solution or is molten.
OIL RIG means oxidation is loss, reduction is gain. Positive ions move to the negative electrode where they gain electrons and are oxidised. Negative electrodes move to the positive electrode where they lose electrons and are reduced.
in a solution; the least reactive ions is formed at the negative electrode eg if it was between hydrogen and aliminium, hydrogen would be displaced. At the positive electrode(i think) because there is hydroxide, it will be formed unless a halide ion is present!
then there is electoplating which is used to make a material look more attractive. The negative electrode is always the item you are covering and the electrolyte must contain the metal ions.
there is the electrolysis of aliminium(bauxide ore). Cryolite is used to lower the melting point which saves electricity and therefore money. Aliminium has a 3+ charge so it moves to the negative electrode where it gains 3 electrons (OIL RIG) and is therefore reduced.
there is also the elevtrolysis of sodium chloride. Sodium chloride+water(pumped into the ground) gives chloride and sodium hydroxide and hydrogen. The hydrogen is used for ammonia and as a fuel. The sodium hydroxide can be used to make bleach, soap and paper. Chlorine can be used to kill microbes in water and to make PVC.
there are also the half equations! I hve a way to learn that. At the positive elevtorde use the equation mx+ + xe- = m. For example 2n*2+ + 2e*- = 2n (that seems so complicated omg) and then for the negative elevtode make sure the charges balance
x
17. Does anyone know the processes in which Esters are made. Thanks.
18. (Original post by fabsafxo)
I think:

1. Comparing fullerenes
2. How to do each chromatography
3. The rate of reactions experiments
4. Collision theory
5. Making salts
6. Electrolysis
I can't imagine any of them being six-markers except perhaps electrolysis The rest could be 2-4 mark questions though? I think Nanoparticles or Catalysts in industry are very likely though.
19. (Original post by zc555)
Does anyone know the processes in which Esters are made. Thanks.
Carboxylic acid+alcohol in the prescene of sulfuric acid catalyst with a water by product
20. (Original post by neil20143)
I can't imagine any of them being six-markers except perhaps electrolysis The rest could be 2-4 mark questions though? I think Nanoparticles or Catalysts in industry are very likely though.
Nanoparticles are just how they have a huge SA:volume and are 1-100NM in size! Theyre good for things like suncream bcause they pass through the body withoutout leaving any white marks in the skin!

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