AS Chemistry- helping each other out!

Reply 1560

Xetter

7

Original post by Nidfeo

OCR B?

If this book is OCR B then yes! 😂

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Reply 1561

Windowswind123

2

Original post by samb1234

If you're doing edexcel you need to understand when you use e/z and when you can use cis/trans as well.

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I thought they were the same thing :confused:

Reply 1562

samb1234

13

They essentially are but you can only use cis trans if the two groups you are describing are the same (eg cl on either side) not if they are different (eg ch3 on one side c2h5 on the other)

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Reply 1563

Xetter

7

Original post by samb1234

They essentially are but you can only use cis trans if the two groups you are describing are the same (eg cl on either side) not if they are different (eg ch3 on one side c2h5 on the other)

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So E/Z and Cis/Trans isomerism are the only types of stereoisomerism right?

Reply 1564

samb1234

13

Original post by Xetter

So E/Z and Cis/Trans isomerism are the only types of stereoisomerism right?

They're the only ones for edexcel but there are other types

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Reply 1565

wednesday_adams

8

" state two essential conditions used for the extraction of aluminium from aluminium oxide "

anyone?

Reply 1566

Windowswind123

2

Original post by samb1234

They essentially are but you can only use cis trans if the two groups you are describing are the same (eg cl on either side) not if they are different (eg ch3 on one side c2h5 on the other)

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Ok, thanks

My teacher marked me down for writing "dimethyl propane" when naming a structure because it should have been "2,2-dimethyl propane". However I thought it was redundant to name it that. I checked the markscheme and actually the "2,2" was in parentheses so it wasn't necessary to write it. I want to check again with people here though whether it is better to include the numbers or not for a three carbon main chain

(edited 9 years ago)

Reply 1567

samb1234

13

Original post by Windowswind123

Ok, thanks

My teacher marked me down for writing "dimethyl propane" when naming a structure because it should have been "2,2-dimethyl propane". However I thought it was redundant to name it that. I checked the markscheme and actually the "2,2" was in parentheses so it wasn't necessary to write it. I want to check again with people here though whether it is better to include the numbers or not for a three carbon main chain

I agree you shouldn't need the 2,2. My guess would be that your unlikely to lose marks for superfluous components of names in this situation but I don't really know (wiki has both names)

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Reply 1568

Windowswind123

2

Original post by samb1234

I agree you shouldn't need the 2,2. My guess would be that your unlikely to lose marks for superfluous components of names in this situation but I don't really know (wiki has both names)

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Maybe it is just a preference.

Reply 1569

samb1234

13

Original post by Windowswind123

Maybe it is just a preference.

It probably is but they should definitely allow both answers

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Reply 1570

C0balt

16

There is no other way of arranging dimethylpropane so there is no reason why you should be marked down for not putting 2, 2

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Reply 1571

Loyota

11

Original post by Xetter

If this book is OCR B then yes! ��

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Ahahah, I think that's OCR A :tongue:

Reply 1572

samwillettsxxx

3

Original post by wednesday_adams

" state two essential conditions used for the extraction of aluminium from aluminium oxide "

anyone?

This will be aluminium oxide (bauxite) extracted by electrolysis :smile:

so the conditions may be
with Molton cryolite to lower melting point
high tenperatures

(edited 9 years ago)

Reply 1573

emilita.nxn

1

How an earth do you answer shape of molecule questions?

( EVERY single question I do I get no marks for it)

Help! :biggrin:

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Reply 1574

samb1234

13

Original post by emilita.nxn

How an earth do you answer shape of molecule questions?

( EVERY single question I do I get no marks for it)

Help! :biggrin:

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Try this if you still need help let me know http://www.chemguide.co.uk/atoms/bonding/shapes.html

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Reply 1575

LittleFaith

9

Original post by wednesday_adams

" state two essential conditions used for the extraction of aluminium from aluminium oxide "

anyone?

The aluminium oxide is electrolysed - so an essential condition is that it must be molten. Another important factor is that it has to be mixed with cryolite - this has a much lower melting temperature so it the resulting mixture takes less energy for it to melt :smile:

That's what you need to know for AQA AS, I don't know about any other exam boards

Reply 1576

wednesday_adams

8

thanks friendd :smile:

Reply 1577

Serine Soul

18

Original post by emilita.nxn

How an earth do you answer shape of molecule questions?

( EVERY single question I do I get no marks for it)

Help! :biggrin:

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Basically a template:

X bonding pairs,
Y lone pairs,
Electron pairs repel,
Lone pairs repel more

Insert X and Y accordingly and you're set :wink:

If they ask for shape, state the shape:

[2 bonding pairs-linear
3- trigonal planar,
4- tetrahedral,
6-octahedral
when there are no lone pairs

2 bonding and 1/2 lone pairs- non-linear
3 bonding and 1 lone pair- pyramidal]

And then repeat the template :lol: