Edexcel Chemistry unit 2 May 2011 (Exam discussion)

Reply 80

warkan

OP

3

Original post by beelz

Am I the only one who thought the gas given off in the ethanethiol question was H2S? What was the actual
question?

Wasn't it something about incomplete combustion ? so I just put Carbon monoxide. :s-smilie:

Reply 81

Alakamind

8

Original post by Machimbawe

the answer is the pparatus is similar to that of cracking,
add cotton wool mixed in both liquids, in testube, with bung and delivery tube and over cold water with inverted testtube. then apply heat to first test tube, gases are released and coolect in inverted test tube.

no you must use a syringe to collect the gas not an inverted test tube, that would cause most of the gas to escape by the time you turn it around. It is a normal distillation reaction with the tube connected to a syringe and with an extra tap on the flask to prevent anygas from escaping when you add the reactants. Chlorine water is colourless and the colour turns to brown when adding potassium iodide.

Reply 82

Great

I drew a reflux with a condernser. Also, i put hcl gas given off andi wrote that you can see fumes coming out of the test tube. Also, for the question about free radical i wrote that they have lone pairs do you think they will accpet that i forgot to say unparied??

Reply 83

F1's Finest

21

Original post by warkan

Wasn't it something about incomplete combustion ? so I just put Carbon monoxide. :s-smilie:

yeah it was carbon monoxide. silly me, when i first saw the question i didnt even think about carbon monoxide as carbon dioxide is a more popular greenhouse gas so i put that down instead, arghhh man im so annoyed, but i should salvage a hard earned A from that, you?

Reply 84

raheem94

13

Original post by warkan

Wow looks like I have lost quite a few marks there :tongue:

. But how would you collect the product in a reflux apparatus? That word made me change the diagram from reflux to distillation :/
What did you write for the jet plane question ? And also the multiple choice with the number of peaks ?
Grade boundaries for 120/120 ? How much is it usually around ?

The substances in the flask will react and move into the condenser where they will be condensed to liquid and will return in the flask. So we could collect the product from flask. If we have to separate the products than we have to carry out distillation but for preparation reflux should be used according to my knowledge. So i don't think that a 3 marks question expects to draw both, distillation and reflux.

The NO released by jet plane will be closer to the ozone layer so it will affect it more while the NO released by cars may not be able to reach ozone because it is too high so it may disslove in rain water forming acid rain.

I answer 3 peaks. The compound contained two bromine atoms so their could be three molecular ion peaks one containing both bromine with RAM of 79, one containing one bromine of RAM 79 and other of 81 and another containing both bromine with RAM 81.

I don't have much idea of unit 2 grade boundaries but i think that about 75/80 will be fine for 120.

Reply 85

Alakamind

8

Original post by James A

yeah it was carbon monoxide. silly me, when i first saw the question i didnt even think about carbon monoxide as carbon dioxide is a more popular greenhouse gas so i put that down instead, arghhh man im so annoyed, but i should salvage a hard earned A from that, you?

what question is this?

Reply 86

ACatCalledMeow

1

Original post by James A

no, increase in pressure increases the rate of the reaction as more collisions take place, hence rate increasing.

didn't you put that down??

Huh? If i'm not mistaken, there were 2 questions on pressure. the first part is the effect, if any, of increasing the pressure on the equilibrium. The next question was the effect of lowering the pressure on the rate of reaction. :s-smilie:

Can anyone verify this? :s-smilie:

Reply 87

F1's Finest

21

i put that the jet engines are produced near the stratosphere, hence a faster break down of the ozone.

Also, i messed up the mean titre, for most past papers you have to use the final reading right ?? i took a mean of that which was like 40 something. i think its wrong but the thing i wanna ask you guys is wether i will get carry on marks.

Reply 88

Alakamind

8

Original post by ACatCalledMeow

Huh? If i'm not mistaken, there were 2 questions on pressure. the first part is the effect, if any, of increasing the pressure on the equilibrium. The next question was the effect of lowering the pressure on the rate of reaction. :s-smilie:

Can anyone verify this? :s-smilie:

they both were related to an increase in pressure, the second one was not a decrase.

Reply 89

Naima100

It's okay, I put chlorine water as colourless as well, because that's what it says in the CGP, it's colourless in water and hexane.
I put reflux cause it said to a high temperature, but maybe it was a delivery tube? :/
I made such a stupid mistake, I wrote NO2 free radicals at first and I thought that NO2 is stable, so I changed it to NO4 lol WTF?
do you think they'll mark the question as a whole or just give you a mark if you have points like NO is regenerated and starts off a chain reaction. and my overall equation was right too.
got the uncertainty MCQ wrong, what about the one about atom economy is 56%, was it B, and was electrophillic addition A or D?
ahh and I couldn't balance that Ag equation cause I wrote H2 -facepalm-
2 marks there.
I wanted a 105-110 in this, don't think it's going to happen.

Reply 90

warkan

OP

3

Original post by Alakamind

no you must use a syringe to collect the gas not an inverted test tube, that would cause most of the gas to escape by the time you turn it around. It is a normal distillation reaction with the tube connected to a syringe and with an extra tap on the flask to prevent anygas from escaping when you add the reactants. Chlorine water is colourless and the colour turns to brown when adding potassium iodide.

My book says when chlorine is dissolved in water it forms a yellow green solution :redface:

Reply 91

F1's Finest

21

Original post by ACatCalledMeow

Huh? If i'm not mistaken, there were 2 questions on pressure. the first part is the effect, if any, of increasing the pressure on the equilibrium. The next question was the effect of lowering the pressure on the rate of reaction. :s-smilie:

Can anyone verify this? :s-smilie:

the first question your right, however the second question said 'how would the pressure affect the rate of reaction'. i dont think it specifically said 'decrease in pressure' , again could someone confirm im right, thanks.

Reply 92

alz333

Original post by James A

yeah it was carbon monoxide. silly me, when i first saw the question i didnt even think about carbon monoxide as carbon dioxide is a more popular greenhouse gas so i put that down instead, arghhh man im so annoyed, but i should salvage a hard earned A from that, you?

it wasnt carbon monoxide because it said the it was complete combustion and it would relase sulfur based oxides which will leads to acid rain acidify lake corrode buildings and statues etc..

Reply 93

Normandy114

11

Original post by ACatCalledMeow

Huh? If i'm not mistaken, there were 2 questions on pressure. the first part is the effect, if any, of increasing the pressure on the equilibrium. The next question was the effect of lowering the pressure on the rate of reaction. :s-smilie:

Can anyone verify this? :s-smilie:

Yes I remember that, except I think it was the effect of increasing pressure on rate. At lest that's what I answered :s-smilie:

Reply 94

ACatCalledMeow

1

Original post by Alakamind

they both were related to an increase in pressure, the second one was not a decrase.

ahhh true, increase in pressure for both question. But one is equlibrium another is the rate! :colondollar:

Reply 95

F1's Finest

21

Original post by alz333

it wasnt carbon monoxide because it said the it was complete combustion and it would relase sulfur based oxides which will leads to acid rain acidify lake corrode buildings and statues etc..

oh rightt, yeah some of my friends told me that after, dammmmitttttt, yeah your right :smile:

Reply 96

Great

No i dont think we had to draw both condenser and reflux we had to draw one which was the reflux and label them correctly it was only 3 marks!

Reply 97

Naima100

Original post by James A

yeah it was carbon monoxide. silly me, when i first saw the question i didnt even think about carbon monoxide as carbon dioxide is a more popular greenhouse gas so i put that down instead, arghhh man im so annoyed, but i should salvage a hard earned A from that, you?

which question was this? section 3?

Reply 98

F1's Finest

21

Original post by ACatCalledMeow

ahhh true, increase in pressure for both question. But one is equlibrium another is the rate! :colondollar:

again, the first question there is no affect on the equilibrium as increasing the pressure will have no effect ( same amount of moles of gas on each side of the equation which cancel out ), again someone confirm this lol