IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: $!$RatJumper$!$ on November 04, 2010, 05:00:46 pm
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Guys how did you find it :)
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Guys how did you find it :)
It was so simple that I made lots of silly mistakes. >:(
But I managed to cover up some of them at the last minute ;D
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thats good.. atleast u covered them up :) how did u find question one.. what were ur gases, volumes and the mr?
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thats good.. atleast u covered them up :) how did u find question one.. what were ur gases, volumes and the mr?
Ooh...........I never expected this kind of question. I messed it up in the beginning but then I finally resolved it. :D
Hmm.........my answers are :
i) Oxygen - 20 cm3 has been used
ii) Carbon dioxide - 10 cm3 has been formed.
A was methane CH4
Did we have to find the Mr in that ???
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wow luck yu.. i just could not find it :( so what are u expecting out of 60 in that paper
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wow luck yu.. i just could not find it :( so what are u expecting out of 60 in that paper
Really? what did you get?
Mr............i think it was another number. i got it to be 42 and the hydrocarbon was propene this time.
Hmm...........i don't know. I think I made a little mistake in the last number and the processes of cracking. Am not sure of my answers for both of them. Otherwise the paper was kinda easy.
I hope to get more than 50. What about you?
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wait is this the paper where they had things on the contact process and stuff? ???
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wait is this the paper where they had things on the contact process and stuff? ???
Contact process??
No, we got something on Haber's process. I guess you sat for another variant. ;)
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my paper has contact process, paper 23, the paper was okay, but i messed up. Deadly King, since you are so awesome, do you know what is the shape of C2O? they asked us to draw it (giving us info- like it should be C-C-O, and no unpaired electrons, and one of the atom is surrounded by only 6 electrons)
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CO2 is linear in shape.
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Oh, C2O is linear in shape as well.
I thought you meant CO2
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my paper has contact process, paper 23, the paper was okay, but i messed up. Deadly King, since you are so awesome, do you know what is the shape of C2O? they asked us to draw it (giving us info- like it should be C-C-O, and no unpaired electrons, and one of the atom is surrounded by only 6 electrons)
Do you have any more details about the question ???
Did it suggest that it is a dimer?
Because oxygen usually has two lone pairs of electrons. If it donates both of them and as well as forming two normal covalent bonds, it will have eight bonded electrons.
No unpaired electrons in the whole molecule or only on carbon or oxygen?
Oh, C2O is linear in shape as well.
I thought you meant CO2
I don't think so. :-[
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The question is about about free radical.. definition, and why NH2 as free radical, its C2O, and not CO2. i don't really get the question, i wrote bent as my answer, :D
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The question is about about free radical.. definition, and why NH2 as free radical, its C2O, and not CO2. i don't really get the question, i wrote bent as my answer, :D
Ahaaaa......now it's clearer.
Compound C2O gotta be : C=C=O
The first carbon atom (left) has two bond pairs of electrons and one lone pair of electron. Hence in all it has 6 electrons around it.
This same carbon will be the radical. ;)
Am afraid the answer is not bent. :-[
Ari was right. It has to be linear.
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Ahaaaa......now it's clearer.
Compound C2O gotta be : C=C=O
The first carbon atom (left) has two bond pairs of electrons and one lone pair of electron. Hence in all it has 6 electrons around it.
This same carbon will be the radical. ;)
Am afraid the answer is not bent. :-[
Ari was right. It has to be linear.
I think i drew it correctly. i wrote bent cos there's lone pair(which i know- its wrong now), its okay.. but why is it linear, is it because as long as there's 2 bond pair, its linear? ignore the lone pairs? (trying to learn, paper 1 left).. :D
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I think i drew it correctly. i wrote bent cos there's lone pair(which i know- its wrong now), its okay.. but why is it linear, is it because as long as there's 2 bond pair, its linear? ignore the lone pairs? (trying to learn, paper 1 left).. :D
C=C=O
Nope, the lone pairs are found on the extreme atoms namely : oxygen and carbon on the left.
Both of them carry a double bond which are taken as one since they go in the same direction.
Hence in whichever direction the lone pairs repel the bond pairs, it won't have any effect.
However if the lone pair had been found on the carbon atom in the middle, then it would have been bent. ;)
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Yes i am correct! hehe, i drew the structure out, comparing H2O and CO2, found out that the difference is the middle atom, Thank you Deadly King, i am sure you will do well in your exam.. you're so good!
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Yes i am correct! hehe, i drew the structure out, comparing H2O and CO2, found out that the difference is the middle atom, Thank you Deadly King, i am sure you will do well in your exam.. you're so good!
Hehe............glad you got it well :D
Anytime...............i really hope so :)
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Ooh...........I never expected this kind of question. I messed it up in the beginning but then I finally resolved it. :D
Hmm.........my answers are :
i) Oxygen - 20 cm3 has been used
ii) Carbon dioxide - 10 cm3 has been formed.
A was methane CH4
Did we have to find the Mr in that ???
Do you remember how many marks this question was worth?
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Do you remember how many marks this question was worth?
Hmm...........can't remember exactly.
But I guess the whole number should have been 5 marks.
Why are you asking?
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That was the only one that i can remember that i got wrong,
I made a stupid mistake somewhere.
I've been going over it again and again in my mind, but don't know where I messed up.
I'm impatiently waiting for the marking schemes to get out
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That was the only one that i can remember that i got wrong,
I made a stupid mistake somewhere.
I've been going over it again and again in my mind, but don't know where I messed up.
I'm impatiently waiting for the marking schemes to get out
Hey don't worry about it now.
You'll only harm yourself by thinking about it over and over again. you won't be able to change anything now. What's already happened cannot be changed. Just chill a bit and concentrate for the rest of your papers. ;)
I think i made some minor mistakes as well :(
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aw dnt worry about it bro.. DK is right, thinking about it cannot change a bit of anything now isnt it. i know how tempting it is to go over the exam in ur head and remember what u got wrong, but whats the point. if it makes u feel better, i didnt manage to get the formula of CH4 nor the volume of the 2 gases. thats like 5 marks gone already. but it doesnt matter one bit because as long as i know i did well in the rest of my paper i feel im getting an A :) DK, which questions do you think u got wrong?
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aw dnt worry about it bro.. DK is right, thinking about it cannot change a bit of anything now isnt it. i know how tempting it is to go over the exam in ur head and remember what u got wrong, but whats the point. if it makes u feel better, i didnt manage to get the formula of CH4 nor the volume of the 2 gases. thats like 5 marks gone already. but it doesnt matter one bit because as long as i know i did well in the rest of my paper i feel im getting an A :) DK, which questions do you think u got wrong?
Hmm...........the two processes of cracking :-[
I was aware of only one process.
The last number as well.............hydrogen hallide. Am not sure about the answers. :-\
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In cracking, one process uses heat, and the other uses a catalyst...right?
The one using heat make a hard polymer, and the one using a catalyst makes a soft polymer like plastic bags.
X was I2 right...so the halide was HI
Did you guys get the same?
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or was it Br2?
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I got my two processes as:
1) Thermal Cracking- Uses 400-900 degrees celsius, 70 atm
2) Catalytic Cracking- Uses 450 degrees celsius, >1 atm, Zeolite Catalyst
For the last question my answers were:
NaBr
Br2
Sulphuric Acid acts as a much better oxidizing agent
What did you guys get?
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But we didn't have to mention conditions, right?
Just saying Temp and catalyst should've been fine. Wasn't that 2 marks?
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But we didn't have to mention conditions, right?
Just saying Temp and catalyst should've been fine. Wasn't that 2 marks?
Nope.
The question actually asked for the conditions of the two different processes.
I didn't know about thermal cracking. :-[
My answers were :
1. Catalytic cracking ---> Temp : 500 and catalyst aluminium oxide
2. Temp : 600 and Silicon dioxide.
Those are similar processes but my teacher somehow told me it might be good. I doubt it though :-\
The last question, i also opted for bromine.
But the other gas, whether sodium bromide or iodide, would have been sulfur dioxide.