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Edexcel - Chemistry Unit 2 - 4 June 2013

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Original post by Maximan12
I would guess B because I can't see a transfer of electrons between any of the atoms


There you go then, correct answer and logic. :smile:
Reply 1061
Avatar for davcha
davcha
1
Water can form 4 hydrogen bonds per molecule because the 2 lone pairs can attract a delta + hydrogen atom each and likewise the molecules hydrogen atoms can do the same, correct? So how comes... 18c jan 2012- why H2O has a higher boiling temp that HF, MS says:
18(c) Water forms (up to) two hydrogen bonds (per molecule but HF only
one).
By my logic aswell, surely HF can form 2 per molecule?
Original post by davcha
Water can form 4 hydrogen bonds per molecule because the 2 lone pairs can attract a delta + hydrogen atom each and likewise the molecules hydrogen atoms can do the same, correct? So how comes... 18c jan 2012- why H2O has a higher boiling temp that HF, MS says:
18(c) Water forms (up to) two hydrogen bonds (per molecule but HF only
one).
By my logic aswell, surely HF can form 2 per molecule?


My question exactly. I always answer it in terms of the number of hydrogen atoms per molecule. Does Ammonia form 3 hydrogen bonds per molecule?

I think it has something to do with repulsion. H30+ forms but you never see H4O2+. :confused:
Reply 1063
Avatar for posthumus
posthumus
OP
20
Can't seem to see how Beryllium oxide is acting as an acid here...

BeO + 2OH- + H2O -----> Be(OH)4 ^2-

Also is beryllium the only group 2 metal which forms BeO layer ?
Or do all of them form oxide layers... except they aren't as strong as berylliums

Also what does the BeO protect it from ? Water? ... what else :smile:

Thanks in advance !
Reply 1064
Avatar for MSamuel
MSamuel
2
i need somewhere to vent my anger so im choosing student room.
i just did a past paper i hadn't done before to see how it went, i made so many stupid bloody mistakes - i never read the question properly - and i lost a good 7 marks. this put me down to a B one off an A.
im so angry at myself, just thought i'd share it with you guys.
any tips on how to help me? apart from the damn obvious "read the question more carefully", none of that please or ill screw at you.
thank you.
Original post by posthumus
Can't seem to see how Beryllium oxide is acting as an acid here...

BeO + 2OH- + H2O -----> Be(OH)4 ^2-

Also is beryllium the only group 2 metal which forms BeO layer ?
Or do all of them form oxide layers... except they aren't as strong as berylliums

Also what does the BeO protect it from ? Water? ... what else :smile:

Thanks in advance !


Lewis theory:

Beryllium oxide accepts lone pair of electrons from hydroxide ions. So, it is acting as an acid here. It's in Unit-4 spec. Not Unit-2. :s-smilie:
Reply 1066
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posthumus
OP
20
Original post by airheadbuster
Lewis theory:

Beryllium oxide accepts lone pair of electrons from hydroxide ions. So, it is acting as an acid here. It's in Unit-4 spec. Not Unit-2. :s-smilie:


Ah yes, thank you !

& I'm an A2 student, so that wasn't very good that I didn't think of that :tongue:
I guess I won't memorize that reaction then...
Can you please please give me a useful link to notes
Is it me, or am I really feeling this exam for tomorrow. :colone:

Also, I've noticed but this thread (compared to others) have alot of people capable of getting A grades. I mean, alot.

Now it's time for me to start section B and C from Jan 13 xD
Original post by MSamuel
i need somewhere to vent my anger so im choosing student room.
i just did a past paper i hadn't done before to see how it went, i made so many stupid bloody mistakes - i never read the question properly - and i lost a good 7 marks. this put me down to a B one off an A.
im so angry at myself, just thought i'd share it with you guys.
any tips on how to help me? apart from the damn obvious "read the question more carefully", none of that please or ill screw at you.
thank you.


Take a deep breath before starting a new question. Try to think from what you have learnt. If you can't do it, don't think too hard. Skip it and get at it later.

The most important thing to do now is to get a good night's sleep. Keep your head cool. You know you can ace it! :smile:
Please give me advices of the most important things that I need to know
My question: Does Ammonia form 3 hydrogen bonds per molecule? :s-smilie:
Reply 1072
Avatar for MSamuel
MSamuel
2
Original post by airheadbuster
Take a deep breath before starting a new question. Try to think from what you have learnt. If you can't do it, don't think too hard. Skip it and get at it later.

The most important thing to do now is to get a good night's sleep. Keep your head cool. You know you can ace it! :smile:


thank you :frown:
just what you need to hear can sometimes help!
I'm feeling that I'm absolutely DOOMED
please I do need help if you can help me
Reply 1074
Avatar for jod.14
jod.14
Hello, can anyone explain this question to me:

A solid gives a red colour in a flame test and reacts with concentrated sulfuric acid to produce steamy fumes, but no other gases. The solid could be:

A) lithium bromide
B) strontium chloride
C) calcium bromide
D) sodium chloride

please help! stressing out!
Original post by upthegunners
go finger the box off yourself to chill out then come back and talk to us

I'm glad there are people like you taking this exam, makes me feel more confident
can some give me tips on how to do redox reactions, my teacher left half way through the course and I dont really understand how to do them :frown:
Original post by Lillian Collins
I'm feeling that I'm absolutely DOOMED
please I do need help if you can help me


Trust me, you need to feel it or else you won't improve. I felt it and that's what made me a consistent guy. :colone:
Reply 1078
Avatar for posthumus
posthumus
OP
20
Original post by airheadbuster
My question: Does Ammonia form 3 hydrogen bonds per molecule? :s-smilie:


I think it's four, but in liquids it's fewer than that... I'd go with 2. But I haven't come across a question where that knowledge is required, have you ?? :frown:


Original post by Lillian Collins
I'm feeling that I'm absolutely DOOMED
please I do need help if you can help me


Just post any questions you have here, and people will answer
Original post by Maximan12
I'm glad there are people like you taking this exam, makes me feel more confident

haha, my level of intellect is vastly broader than yours.

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