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

1. (Original post by mimibrockstark)
Can someone tell me how they solved the empirical formula because I am confused on how my answer was different. C2.
Pb= 6.21g and O=0.72g
Pb's Ar= 207 and O's= 16
6.21/207=0.03 Moles
.72/16=0.045 Moles

0.03/0.03=1
0.045/0.03=1.5
So the ratio is 1:1.5
to get whole numbers, multiply both sides by 2 to get 2:3
so the formula is Pb2O3
2. What did everyone put for the soft water 6 marker?

I put CaCO3 in Method 2 must be removed....

but I made nonsense for the advantages, for example, I wrote limestone/CaCO3 can be collected (when this method is done on an industrial scale) and used for buildings preserving existing reserves of limestone.
4. (Original post by mimibrockstark)
Different temps/different conditions.
5. Is it possible for a student to get a* even with a D in one of the units?

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6. (Original post by mimibrockstark)
Change the conditions- low density high temperature, high pressure and no catalyst and the opposite for high density
7. (Original post by bananabrain12345)
No you have to get at least c in that unit and a*s in the others
what UMS did you get in the D unit ?
8. What did people get for the total energy change and the Q=MCdeltaT question on the C3 paper?
9. (Original post by MrTechGamer)
Can you please respond to my post ?
Regards ,
Someone who is not a chav
I'm afraid not. Maybe an A at tops as a D mean 40UMS. You would need 360 UMS to get a an a*.
10. Hey, the reactants were all used up so the rate of reaction couldn't increase, despite the increase in temperature.
11. (Original post by thomasallen)
To be honest I'm so happy that it looks like I got the empirical formula one right, as well as a few of the other difficult ones in C2. Really wasn't expecting to do as well as it looks like I did, since everyone at my school was so negative about C2 like it was some impossible paper or something.
ahaha are you serious? everyone at my school thought c2 was easy, oh well. lets just pray
12. (Original post by tombirchy)
I'm afraid not. Maybe an A at tops as a D mean 40UMS. You would need 360 UMS to get a an a*.
Whoops .. the post wasn't intended for you , it was intended for that drugee ganaja or ganaja man/chav thing ?
13. (Original post by TheKevinFang)
Hey, the reactants were all used up so the rate of reaction couldn't increase, despite the increase in temperature.

I wrote something like the maximum energy increase from (making bonds- breaking bonds) has been achieved.
14. (Original post by hld123)
What did people get for the total energy change and the Q=MCdeltaT question on the C3 paper?
4620J
15. HAHAHAHAHA .. good one
16. (Original post by mareyak)
Would i get the mark for saying that that copper corrodes, which is why it cant be used as a coin.
I think it was because pure copper is too soft
17. Do you think they would accept just carbon instead of carbon-12 for the question in C2?
18. (Original post by hld123)
What did people get for the total energy change and the Q=MCdeltaT question on the C3 paper?
I got around 4000/5000 something I think! I wasn't sure if I'd done the previous two parts correct though so that probably isn't right
19. (Original post by mghp)
I think it was because pure copper is too soft
Same
20. (Original post by mimibrockstark)
I thought the empirical formula was diving the relative atomic number with the amount needed? How is it Pb2O3?
you had to divide something like 0.7g by oxygen-16 i think which came out at pb2o3 once u x1000 and divided

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