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Edexcel - Chemistry Unit 2 - 4 June 2013

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Original post by HarryMWilliams
Nope, I think you have it correct with D. :smile:
phew - I've been worrying over that question, as it was a complete guess :biggrin: from what you saw of the paper, how did it compare to the others? I found it hard, so fingers crossed for low grade boundaries
Original post by HarryMWilliams
Nope, I think you have it correct with D. :smile:


Sadly, I think the correct answer was C, which lucky is what I put as I wasn't sure either. However, I believe C was correct as the second electron affinity of oxygen is positive.

This is highlighted at the bottom of this page on chemguide if you want to see for yourself:

http://www.chemguide.co.uk/atoms/properties/eas.html

Oh well, I wouldn't worry about getting this wrong, as it is only one mark and is a difficult first question. :smile:

Good Luck in Unit 2, hope it is a good paper. :biggrin:
Original post by Baraf
I can't believe it, to get an A* you need 270ums out of the 300ums for A2..that is mission impossible, your only allowed to miss 30ums ?? seriously ??

thank God my practical went well, hopefully I will pick up on all the 60ums, but still got another 210 ums that I need to get to qualify for the A*


It's possible, but requires alot of hardwork. Of course, the people that find chemistry easy are more likely to be hitting A's and A*'s pretty easily.

One of my mates got an A* for Chem and is in uni now (doing Dentistry). Him and I were fairly close in terms of ability but he was able to make more effective use of his revision time, hence he was prepared well for the Unit 4 and 5 exams, along with the A2 practical.
Reply 183
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Baraf
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Original post by James A
It's possible, but requires alot of hardwork. Of course, the people that find chemistry easy are more likely to be hitting A's and A*'s pretty easily.

One of my mates got an A* for Chem and is in uni now (doing Dentistry). Him and I were fairly close in terms of ability but he was able to make more effective use of his revision time, hence he was prepared well for the Unit 4 and 5 exams, along with the A2 practical.

I got an A in unit 1 so only retaking unit 2, do you reckon I should cover the unit one specification in preparation for unit 4-5, I am not worried about getting an A overal, its the A* which will be hard to achieve.

and I really need an A* in Chemistry to compensate my pending C grade in Physics lol.
Reply 184
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wbrian
Original post by HarryMWilliams
Nope, I think you have it correct with D. :smile:

isnt the 1st electron affinity negative always
Reply 185
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wbrian
Original post by rockstar101
Haha lol i loved the cooking question. I was like yes free marks. Was good overall. My teacher has the paper n i cnt see a mistaken anywhere apart from my cracking of dodecane drawing lol.
Nervous for unit 2. Do u guys have any good notes. Please post it up as i relii need it.

Hw did every1 else find unit 1
Any guesses on grade boundary for full UMS?
:smile:

ohhh what was the answer for that cooking thing :frown:
Reply 186
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wbrian
does anyone have an unofficial mark scheme for unit 1
Reply 187
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wbrian
can anyone remember the calculation answers in unit 1
Reply 188
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Baa
Hii, does anyone have a summary table/revision notes for reactions of groups 2 and 7 and the trends for them?
Thank youu!!! :smile:


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Original post by wbrian
ohhh what was the answer for that cooking thing :frown:

When it decomposes due to heat it produces co2 which makes the cake rise and soft. Lol. Dw
Reply 190
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Gunner121
Hi , for shapes of molecules how do we know whether the molecule has double bonds or single bonds and if molecules like CO3^-2 , NO3^-1, NH4^+1 etc comes what do we have to do with the charge and how do we draw the shape , please someone help in this
Reply 191
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Baraf
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Original post by Gunner121
Hi , for shapes of molecules how do we know whether the molecule has double bonds or single bonds and if molecules like CO3^-2 , NO3^-1, NH4^+1 etc comes what do we have to do with the charge and how do we draw the shape , please someone help in this


interesting question, well I I know how it works for NH4+1 but CO3-2 always confused me.

so Carbon(C) is the central atom, it has 4 electrons it can share, it shares 2 with one Oxygen in a double bond, and forms a single bond with each O- right because they have 7 electrons and only need 1 each, so the carbon shares its 2 remaining electrons with them.

this is how i understand it.

the shape would be trigonal planar, because there are 3 bond pairs and no lone pairs, so the 3 oxygen around the carbon form a trigonal planar with bond angle 120.

does anyone know how this relate to bond length >?
Original post by ConorMorris
Sadly, I think the correct answer was C, which lucky is what I put as I wasn't sure either. However, I believe C was correct as the second electron affinity of oxygen is positive.

This is highlighted at the bottom of this page on chemguide if you want to see for yourself:

http://www.chemguide.co.uk/atoms/properties/eas.html

Oh well, I wouldn't worry about getting this wrong, as it is only one mark and is a difficult first question. :smile:

Good Luck in Unit 2, hope it is a good paper. :biggrin:


I remembered something about electron affinity being negative, but the first and second confused me :tongue: Thanks for clarifying it and good luck to you too!
Reply 193
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k.assen
Hey guys! Good luck to all with revision! Does anyone know if there is revision notes for this unit that can be downloaded?

Best regards :smile:
Hi everyone, I have come across a question I'm not sure about. Why is it possible to have hydrogen bonding it water and Hydrogen Floride but not in Hydrogen or Methane? If any of you could shed some light, that would be great :biggrin:


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Original post by Baraf
interesting question, well I I know how it works for NH4+1 but CO3-2 always confused me.

so Carbon(C) is the central atom, it has 4 electrons it can share, it shares 2 with one Oxygen in a double bond, and forms a single bond with each O- right because they have 7 electrons and only need 1 each, so the carbon shares its 2 remaining electrons with them.

this is how i understand it.

the shape would be trigonal planar, because there are 3 bond pairs and no lone pairs, so the 3 oxygen around the carbon form a trigonal planar with bond angle 120.

does anyone know how this relate to bond length >?


Ok it is trigonal planar by the carbon atom forms 2 double bonds with two xygen atms and then the third oxygen provides its lone pair of electrons to form a dative bond thus the 2- value of co3 if im not wrong :smile:
Not sure if im right. Really confused now :s
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posthumus
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Original post by Cattey watty
Hi everyone, I have come across a question I'm not sure about. Why is it possible to have hydrogen bonding it water and Hydrogen Floride but not in Hydrogen or Methane? If any of you could shed some light, that would be great :biggrin:


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You mean why hydrogen bonding is not possible with hydrogen or methane?

Well firstly hydrogen is a gas in it's standard state... also it's not polar at all.
The Hydrogen atoms in Methane (or pretty much all alkanes for that matter) are not sufficiently delta positive.
Reply 198
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ramanan
Original post by Cattey watty
Hi everyone, I have come across a question I'm not sure about. Why is it possible to have hydrogen bonding it water and Hydrogen Floride but not in Hydrogen or Methane? If any of you could shed some light, that would be great :biggrin:


Posted from TSR Mobile


A hydrogen bond is the interaction between polar molecules in which hydrogen (H) is bound to a highly electronegative atom, such as nitrogen (N), oxygen (O) or fluorine (F), H bond is Polar Covalent bond.

H-H bond has no electronegativity difference. Methane has Non polar covalent bond. bcz their difference

679fdbbd60e31f9fd4067f5f482a8f2c.jpg
Reply 199
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zyxwvuts
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Can someone tell me the colours of Bromine gas, Bromine in aqueous solvent, and Bromine in hydrocarbon? Thanks.

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