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Ocr f321 23 may 2013~official discussion thread

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Original post by ADAOBI123
would that come up on the exam ? :s-smilie:


There could always be the possibility of it appearing, but quite unlikely really. :smile:


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Original post by MathsNerd1
There could always be the possibility of it appearing, but quite unlikely really. :smile:


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phew, but I'll look over it later on :smile:
Original post by ADAOBI123
phew, but I'll look over it later on :smile:


Same here :smile:


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One thing i do not understand is that SF6 has bond angles of 90 degrees. could someone please explain why that is?
I've done all the past paers, but does anyone know where I can get more questions for free online? (particularly calculations) Thanks :smile:
Original post by Dr. Django
I've done all the past paers, but does anyone know where I can get more questions for free online? (particularly calculations) Thanks :smile:


http://www.a-levelchemistry.co.uk/OCR%20Chemistry%20A/Unit%201/Unit%201%20resources.html

This helped for me
Original post by ADAOBI123


Thanks :smile: That looks great
Original post by Dr. Django
Thanks :smile: That looks great


Welcome
Original post by gettingcreamy
One thing i do not understand is that SF6 has bond angles of 90 degrees. could someone please explain why that is?


I'm not sure why really, just that is forms 4 bonds in the same plane and 2 vertically opposite eachother which gives the bond angle of 90 degrees between each bond.


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Reply 169
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sladyy96
Original post by gettingcreamy
One thing i do not understand is that SF6 has bond angles of 90 degrees. could someone please explain why that is?

because if the angle was any smaller the electrons wouldn't be as far apart as possible, and the same for if the angle was bigger - as it would mean the electron is getting closer to a different electron (the angle increases on one side and decreases on the other). Remember electrons repel each other as much as possible. Hope this helps :smile:
Original post by gettingcreamy
One thing i do not understand is that SF6 has bond angles of 90 degrees. could someone please explain why that is?


Imagine the molecule as a 3D shape and not 2D.
http://www.3dchem.com/inorganics/SF6.jpg

In this way you can see that the molecule has 90 degree bond angle between each atom.
Original post by Tom Winfield
Imagine the molecule as a 3D shape and not 2D.
http://www.3dchem.com/inorganics/SF6.jpg

In this way you can see that the molecule has 90 degree bond angle between each atom.


Thanks. Good one :biggrin:
Bond angles and shapes are fine for the most part, but i was doing a paper that was about hydrazine and they asked for the bond angle of "N-H-N" or something like that... thats when it got confusing. Also in the january 2013 paper a similar question came up with the "O-B-O" bond angle or whatever.
Reply 173
Avatar for Shanze S
Shanze S
anyone know where the mark scheme for the specimen paper is ?
I just came out of psychology and have this whole topic to do in a few hours. No part paoers although I done them in january and was getting a's but in actual exam I got a D. Test is much harder than past papers

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Reply 175
Avatar for sladyy96
sladyy96
can someone please explain hydrogen bonding?
Original post by Shanze S
anyone know where the mark scheme for the specimen paper is ?


Just scroll underneath the questions. The mark scheme is there
Question

Explain the decrease in atomic radius across each period?
Predict and explain whether a sodium ion is larger or smaller than a sodium atom.
Why does the boiling point increase from Sodium to Aluminium?
I use a nifty mneumonic which is weird- SSPIRD - similar shielding,protons increase,radii decreases and FIE increases - down groups I just say radius,sheilding,shells and protons increases but FIE decreases


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Reply 179
Avatar for Harryshah
Harryshah
I'm going to have a hard time waking up for this exam :frown: My sleeping patterns are soo bad!

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