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OCR B Salter's Chemistry by Design F335 - 15th June 2015

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Original post by lastminutelarry6
I put the wrong angle for the H-S-H bond, would i still get the marks for writing about minimum repulsion?


Wasn't it H-N-H bond? and I think you'd get 2/3.
Original post by lastminutelarry6
I put the wrong angle for the H-S-H bond, would i still get the marks for writing about minimum repulsion?


It was a 4 mark question so you'd probably get marks if you mentioned areas of high electron density, but it's maximum repulsion, no? They repel as far apart as possible.
Guys for the pressure question, what direction did the equilibrium position move and did the yield increase or decrease
Original post by whenthecatcalls
Guys for the pressure question, what direction did the equilibrium position move and did the yield increase or decrease


Position of equilibrium shifts to forward reaction as there is fewer molecules on RHS
The one on temp, equilbrium constant decreases?
what was the H-N-H bond angle?
Original post by chococup123
what was the H-N-H bond angle?


109, 4 regions of electron density
Original post by chocbrownie
The one on temp, equilbrium constant decreases?


Yup, forward reaction was exothermic so back reaction favoured and yadda yadda yadda.

Temp. under 250 wasn't used as rate of reaction greater at higher temperatures. More kinetic energy, more frequent collisions etc.
Done this in MS Excel real quick. As you guys can see, just based on the polls right now. There's a huge difference between F334 and F335.

I think the most interesting one is that 80% ofn those polled for F334 said it was hard or very hard
Chem_Exam_Data.PNG
Original post by johnny147
109, 4 regions of electron density


Whaat there was only 3 regions of electron density? there was an electron on its own, wasn't there?
Original post by chococup123
Whaat there was only 3 regions of electron density? there was an electron on its own, wasn't there?


There was 4 if i remember correctly. 2 N-H bonds, 1 N-C bond, and 1 lone pair (since amines always have a lone pair)
(edited 8 years ago)
Original post by chococup123
Whaat there was only 3 regions of electron density? there was an electron on its own, wasn't there?


Four areas of electron density. Two N-H bonds, a C-N bond and a lone pair.
Original post by johnny147
Position of equilibrium shifts to forward reaction as there is fewer molecules on RHS


Oh ok, thanks! I think I got that question right :smile:
Original post by Little Tail Chaser
Four areas of electron density. Two N-H bonds, a C-N bond and a lone pair.


ohh you had to count the C-N too? :frown: :frown:
Original post by chococup123
ohh you had to count the C-N too? :frown: :frown:


You have to consider all areas of high electron density around N, so yeah.

If you mentioned areas of HED repelling as far apart as possible then I'm sure you got some of the marks, don't worry about it. :smile:
Original post by Little Tail Chaser
You have to consider all areas of high electron density around N, so yeah.

If you mentioned areas of HED repelling as far apart as possible then I'm sure you got some of the marks, don't worry about it. :smile:


yeah I did, aww thank youu! :smile:
Vote Now, How did you find this exam!!!

http://www.thestudentroom.co.uk/show....php?t=3406085
Original post by johnny147
Position of equilibrium shifts to forward reaction as there is fewer molecules on RHS


Oh thank you!. I thought I misread the question.
Original post by Diamond Crafter
I think what she means is (or at least the part that got me) was the fact that it's understood that ice is less dense than water but it's the "at the same temperature" part as logically ice and water don't exist at the same temperature because the whole point of it being "ice" is that the temperature has been reduced to a point where water has changed state. However if the textbook meant in hypothetical terms that if water and ice were to exist in the same temperature then ice would be less dense than water due to the spaces that exist. I think! If I've just confused things even more then I'm sorry! :redface:


Na, makes sense but that stuff didnt come in the exam !

How'd you find it though?
Original post by rm19
For the last question, it could also be heat with fehling's solution and it would be red when it turns into a carboxylic acid?


I think that would be fine. I was going to put that but I wasn't sure how to spell fehling solution, so went for acidified dichromate + reflux! It did say 'one of the reactions', so that implied there was more than one possible answer. :P

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