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

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Original post by radhikagulati
For NMR do you just talk about what the ppm value relates to and splitting? What else can you talk about?


for nmr i think if they give you a diagram showing the splitting then mention it, talk about the chemical shifts and number of proton which represents the area of the peak
Original post by docdoc02
for nmr i think if they give you a diagram showing the splitting then mention it, talk about the chemical shifts and number of proton which represents the area of the peak


How do we know the number of proton that represent the area of the peak?
Original post by radhikagulati
How do we know the number of proton that represent the area of the peak?


they would give a number on top of each peak like 6H
Original post by docdoc02
they would give a number on top of each peak like 6H


Oh yeah I've seen that before and then you can use it to find the proton ratio
Thank you!
Original post by radhikagulati
Oh yeah I've seen that before and then you can use it to find the proton ratio
Thank you!


yes basically
Original post by greencat55
Sorry to ask again, but I'm stumped again. :/
Does anyone know how to get the answer to (ii). The mark scheme said it is 2.73.
Part (i) is right and please ignore my scribbles :P
Thank you!! :smile:

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What paper is this from?
So I don't get this.
In CI on page 105 it says -
'The density of ice at 273K is less than the density of water a the same temperature'
Huh??
Anyone help here?
Original post by Shostakovish
So I don't get this.
In CI on page 105 it says -
'The density of ice at 273K is less than the density of water a the same temperature'
Huh??
Anyone help here?


Correct me if im wrong but when ice is formed, the hydrogen bonds still exist but they are more spread out and there are large open spaces between water molecules in ice , hence they have a lower density than water.

I THINK he says :smile:
Original post by Diamond Crafter
What paper is this from?


Jan 2012

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Original post by suyoof123
Correct me if im wrong but when ice is formed, the hydrogen bonds still exist but they are more spread out and there are large open spaces between water molecules in ice , hence they have a lower density than water.

I THINK he says :smile:



I get that part, but I meant the part where it says 'at the same temperature'Ice is just liquid water in another form though, right? I don't understand this.
Anyone got the F335 June 2014 question paper & mark scheme please?
Original post by Shostakovish
I get that part, but I meant the part where it says 'at the same temperature'Ice is just liquid water in another form though, right? I don't understand this.


Thats it,

When water is in the form of ice, then those large empty spaces exist, they dont exist when water is in liquid form

so think of it as when water is ice, there is less 'water' in a certain space due to empty spaces but when water is 'water' and not ice, then those empty spaces dont exist, hence water has a higher density than ice.

Hope thats clear :smile:
Original post by MattBrockle
Anyone got the F335 June 2014 question paper & mark scheme please?


Here you gooo ^.^
F335-01 Jun14.pdf248.9KB
F335_MS_Jun14.pdf472.0KB
Original post by Shostakovish
Here you gooo ^.^


you are a very good person i wish you good health for the rest of your life
Original post by Shostakovish
I get that part, but I meant the part where it says 'at the same temperature'Ice is just liquid water in another form though, right? I don't understand this.


Original post by suyoof123
Thats it,

When water is in the form of ice, then those large empty spaces exist, they dont exist when water is in liquid form

so think of it as when water is ice, there is less 'water' in a certain space due to empty spaces but when water is 'water' and not ice, then those empty spaces dont exist, hence water has a higher density than ice.

Hope thats clear :smile:


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:
Original post by Shostakovish
So I don't get this.
In CI on page 105 it says -
'The density of ice at 273K is less than the density of water a the same temperature'
Huh??
Anyone help here?


yeah i think its a mistake, ive read that bit over few times and it doesnt make much sense for liquid water and ice to have a difference of density at the same temperature :P
I dont feel ready.
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:

But water does exist as both ice and liquid at the same temperature? On a cold day the top of a pond will freeze over but there will still be water underneath. In fact water exists as all three states at the same temperature, water vapour in the air, liquid as the pond, and solid as the frozen top of the pond (its even got a special name and occurs for other molecules as well - the triple point)
With NMR spectroscopy I understand how the peaks split but how close do the next hydrogens have to be to have an effect on the splitting? Is it only the immediate neighbouring hyrdrogens?
Sorry to burst in, but is phenylammine the same as aminobenzene?

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