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# AS Chemistry- helping each other out! watch

1. (Original post by ilovecake123)
so the moles of o2 is 1.5/24? = 0.0625
b) so2 = 3/24 =0.125
c) how do you use the mole ratio?
Solution above. 2 moles of SO2 react with 1 mole of O2.
So 0.0625 mol of O2 SHOULD react with 0.125 mol of SO2 (going with the mole ratio).
Oh, look, it does! If it didn't, then something would be in excess and it would get a bit more complicated.
2. So everyone here is doing Unit 1 in Jan ryt? Which is nxt week on the 7th......
3. Hi,
Do any of you have the answers to the AQA AS Chemistry unit 1 practice exam questions from that textbook by nelsom thornes? I have asked my teacher but havent recived a reply. Any help ??
Thank you
4. Anyone doing Edexcel here folks???
5. (Original post by abdullahharis)
Anyone doing Edexcel here folks???
yhhh fam
6. Best way to understand curly arrow mechanisms??
Best way to understand curly arrow mechanisms??
There is not that much to understand? You can pretty much just memorise them?
8. (Original post by BBeyond)
They're not that much to understand? You can pretty much just memorise them?
I always lose marks with them questions
9. hi please can someone help me out with this question
thanks

5 When 0.635 g of copper (relative atomic mass, RAM = 63.5) is added to an excess of

silver nitrate solution, 2.158 g of silver (RAM = 107.9) form. The ionic equation for the

reaction is

A Cu(s) + Ag2+(aq) Cu2+(aq) + Ag(s)

B Cu(s) + Ag+(aq) Cu+(aq) + Ag(s)

C 2Cu(s) + Ag2+(aq) 2Cu+(aq) + Ag(s)

D Cu(s) + 2Ag+(aq) Cu2+(aq) + 2Ag(s)
10. Chem is the only subject I can be bothered to revise RIP me in economics.
Best way to understand curly arrow mechanisms??
What in particular don't you understand about them? Curly arrows denote the movement of a pair electrons from one species to another.

Generally acceptors of lone pairs have a positive charge on the species, that's another way of remembering.

Feel free to post an example of a mechanism that you need help understanding.
12. (Original post by ilovecake123)
hi please can someone help me out with this question
thanks

5 When 0.635 g of copper (relative atomic mass, RAM = 63.5) is added to an excess of

silver nitrate solution, 2.158 g of silver (RAM = 107.9) form. The ionic equation for the

reaction is

A Cu(s) + Ag2+(aq) Cu2+(aq) + Ag(s)

B Cu(s) + Ag+(aq) Cu+(aq) + Ag(s)

C 2Cu(s) + Ag2+(aq) 2Cu+(aq) + Ag(s)

D Cu(s) + 2Ag+(aq) Cu2+(aq) + 2Ag(s)
What's the charge of the nitrate ion on it's own? If you know that, then the rest is straightforward.
13. (Original post by James A)
What's the charge of the nitrate ion on it's own? If you know that, then the rest is straightforward.
You don't use the nitrate ion for this question!

Calculate moles of each metal and find the coefficients of the equation and hence the ratio in which they react...
14. Very fortunately my teacher is one of the head examiners for OCR. If anyone has any questions on exam technique etc. feel free to ask (so that I can ask her).
15. (Original post by charco)
You don't use the nitrate ion for this question!

Calculate moles of each metal and find the coefficients of the equation and hence the ratio in which they react...
Ah yes, completely forgot about the values given haha. I was so poor at inorganic chem during my A-level days
16. I'm doing AQA
1. 2 Complete combustion of 50 cm3 of a hydrocarbon vapour gave 350 cm3 of carbondioxide, both gas volumes being measured at the same temperature and pressure. Theformula of the hydrocarbon could be
A C8H18B C7H16C C6H14D C5H12

how do you do this question?

17. (Original post by ilovecake123)
1. 2 Complete combustion of 50 cm3 of a hydrocarbon vapour gave 350 cm3 of carbondioxide, both gas volumes being measured at the same temperature and pressure. Theformula of the hydrocarbon could be
A C8H18B C7H16C C6H14D C5H12

how do you do this question?

This is the correct place.

Use Avogadro's law and the corresponding Gay Lussac law of combining volumes.
18. (Original post by charco)
This is the correct place.

Use Avogadro's law and the corresponding Gay Lussac law of combining volumes.
what is gay lussac law? I've never learnt it
19. (Original post by ilovecake123)
what is gay lussac law? I've never learnt it
Avogadro's law says that equal volumes of gas under the same conditions of temperature and pressure contain the same number of moles.

Gay Lussac extended this to say that you could use the coefficients of an equation where gases are reacting as volumes instead of moles.

Hence:

CxHy --- combustion ---> xCO2

The volume of carbon dioxide formed must be 'x' times the volume of hydrocarbon burned.

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