Edexcel - Chemistry Unit 2 - 4 June 2013

OP

Didn't get an A or anything... but the exam was better than other Chemistry exams that I've sat in the past year. Didn't need an ambulance or anything afterwards :tongue:

But didn't do so well either :redface:

I think I may have lost up to 30 marks. The multiple choice was particularly hard compared to past ones !

Reply 1381

airheadbuster

2

Original post by posthumus

Didn't get an A or anything... but the exam was better than other Chemistry exams that I've sat in the past year. Didn't need an ambulance or anything afterwards :tongue:

But didn't do so well either :redface:

I think I may have lost up to 30 marks. The multiple choice was particularly hard compared to past ones !

30!

Reply 1382

posthumus

OP

20

Original post by airheadbuster

30!

Yh just keeping it safe :tongue:

I don't do very well in Chemistry exams :redface:

What do you guys recon grade boundaries will be like?

EDIT: 2 question I completely missed out what could you do to chlorobutane whatever to turn it in alcohol with NaOH. & the one with ppm. Which is better than usual... where it's typical of me to leave half the paper blank :tongue:

(edited 10 years ago)

Reply 1383

Sciencefella

I know of like 6 marks that I've lost. But it was a very reaction based paper

Posted from TSR Mobile

Reply 1384

airheadbuster

2

Original post by posthumus

Yh just keeping it safe :tongue:

I don't do very well in Chemistry exams :redface:

What do you guys recon grade boundaries will be like?

EDIT: 2 question I completely missed out what could you do to chlorobutane whatever to turn it in alcohol with NaOH. & the one with ppm

PPM = (2.2/1000) x 10^6 :colone:

Remember the former one was about chlorobutane in water which means hydrolysis. Cl- ion will react with silver ion to form white ppt. Not sure though. :confused:

Reply 1385

TheBigGeek

9

Do we want to start an unofficial markscheme? Disagree with me where you feel differently!

I'm pretty sure the thiosulphate calculations went like this:
=0.00116
=0.00058
=0.0125
=0.01192
=13.8%

And I think the percent error was 0.86%...

The question with the mechanism was:
=The solution would be dissolved in ethanol
=It was elimination
=The solution would be dissolved in water
=It was the Sn2 mechanism

The first section 2 question was Ba(s) + 2H2O (l) ---> Ba(OH)2 (aq) + H2 (g)
The Ba changed oxidation number from 0 to +2
And the H changed from +1 to 0 (though it stayed the same in the hydroxide)

Then it was Ba(OH)2 + 2HCL ---> BaCl2 + 2H2O

The difference would a white precipitate
Because Barium sulphate is insoluble and Barium hydroxide is extremely soluble.

Bonding questions:
18 electrons
London forces
Both have London forces, though the one that's not F2 has permanent dipoles
HF has hydrogen bonding, which is the strongest intermolecular force
The Cl atom in HCl is too big to H bond, so doesn't form H bonds, so won't have the highest boiling point

Questions following the little article
(This one I'm totally not sure about!) It came out as 2200ppm, and 2200 > 60 so richer in bromine.
More carbonate ions, less CO2, as more hydrogen carbonate ions were produced to use up the excess carbonate.
Mechanism for global warming (what are the marks for here?!): Molecules with polar bond absorb IR which means that the Sun's rays are trapped in the atmosphere when they are reflected off the earth
Assorted bull**** for the last 4 marker.

The equilibria stuff
(Again, not sure about this one) The HCl donated H+ ions to the equilibrium mixture, moving the equilibrium to the left and meaning that more bromine is formed rather than hydrolysed
Temp increase it moved to the right because the forward reaction was endothermic and a temp increase favours the endothermic reaction
Features of dynamic equilibrium, I put (not sure about this):
-At a molecular level there is ceaseless change
-To the naked eye, there is no change in the solution

The multiple choice were (assorted answers, though as much in order as I can remember)
SF6
CCl4
2-chlorobutane
Potassium nitrate
Ozone depletion
A for the titration multiple choice question
The most common energy of the molecules

Reply 1386

posthumus

OP

20

Original post by geor

I put aqueous conditions and I think 2200...?
I think grade boundaries will probably be high but lower than january

Posted from TSR Mobile

Original post by airheadbuster

PPM = (2.2/1000) x 10^6 :colone:

Remember the former one was about chlorobutane in water which means hydrolysis. Cl- ion will react with silver ion to form white ppt. Not sure though. :confused:

Ah damn I did that initially but then I thought ppm was 10^-6 :frown:

& changed it... Oh well both were only 1 marks. But I lost more as well :tongue:

I think grade boundaries will be 62-64 / 80 for an A

Reply 1387

airheadbuster

2

Original post by airheadbuster

Why does NaCl dissolve in water instead of alcohol?
Why does fullerene dissolve in petrol while graphite and diamond do not?

There was another question about carbon neutral that I don't think I answered right.

What did you guys answer these 3?

Reply 1388

Goods

16

I did an sn1 mechanism I'm not sure if it should have been sn2 it was a secondary haloalkanes :I

Posted from TSR Mobile

Reply 1389

airheadbuster

2

Original post by TheBigGeek

Do we want to start an unofficial markscheme? Disagree with me where you feel differently!

I'm pretty sure the thiosulphate calculations went like this:
=0.00116
=0.00058
=0.0125
=0.01192
=13.8%

And I think the percent error was 0.86%...

The question with the mechanism was:
=The solution would be dissolved in ethanol
=It was elimination
=The solution would be dissolved in water
=It was the Sn2 mechanism

The first section 2 question was Ba(s) + 2H2O (l) ---> Ba(OH)2 (aq) + H2 (g)
The Ba changed oxidation number from 0 to +2
And the H changed from +1 to 0 (though it stayed the same in the hydroxide)

Then it was Ba(OH)2 + 2HCL ---> BaCl2 + 2H2O

The difference would a white precipitate
Because Barium sulphate is insoluble and Barium hydroxide is extremely soluble.

Bonding questions:
18 electrons
London forces
Both have London forces, though the one that's not F2 has permanent dipoles
HF has hydrogen bonding, which is the strongest intermolecular force
The Cl atom in HCl is too big to H bond, so doesn't form H bonds, so won't have the highest boiling point

Questions following the little article
(This one I'm totally not sure about!) It came out as 2200ppm, and 2200 > 60 so richer in bromine.
More carbonate ions, less CO2, as more hydrogen carbonate ions were produced to use up the excess carbonate.
Mechanism for global warming (what are the marks for here?!): Molecules with polar bond absorb IR which means that the Sun's rays are trapped in the atmosphere when they are reflected off the earth
Assorted bull**** for the last 4 marker.

The equilibria stuff
(Again, not sure about this one) The HCl donated H+ ions to the equilibrium mixture, moving the equilibrium to the left and meaning that more bromine is formed rather than hydrolysed
Temp increase it moved to the right because the forward reaction was endothermic and a temp increase favours the endothermic reaction
Features of dynamic equilibrium, I put (not sure about this):
-At a molecular level there is ceaseless change
-To the naked eye, there is no change in the solution

The multiple choice were (assorted answers, though as much in order as I can remember)
SF6
CCl4
2-chlorobutane
Potassium nitrate
Ozone depletion
A for the titration multiple choice question
The most common energy of the molecules

First one is correct.

>Cl atom is too big.

It will be the electronegativity difference between CL and H is not high enough to make hydrogen sufficiently &+. So, there will be no hydrogen bonding in HCl which means it will have lower boiling point.

Features of dynamic equilibrium:

1. The rate of forward reaction is equal to the rate of backward reaction.
2. The concentration of the species on both sides of the reaction will be unchanged.

IR:

They absorb IR emitted from Earth's surface and re-radiates it back to Earth, contributing to global warming.

Reply 1390

F1's Finest

21

I thought that was a decent paper. I talked alot of bull for the very last question.

For the mechanism I did Sn1 as that is what secondary alcohols tend to go by.

The multiple choice was fairly challenging.

I reckon I lost about 10 to 12 marks.

Reply 1391

posthumus

OP

20

Original post by airheadbuster

What did you guys answer these 3?

Why does NaCl dissolve in water instead of alcohol?
Why does fullerene dissolve in petrol while graphite and diamond do not?

There was another question about carbon neutral that I don't think I answered right.

1) Because of hydration enthalpy
2) can't remember options
3) Got this one wrong... forgot to come back to it & the pesticide should have been taken into consideration

Reply 1392

GCSE-help

6

I think they would accept both mechanisms for the secondary haloalkane?

Reply 1393

F1's Finest

21

For dynamic equilibrium I said that:

There is no change to the concentrations of the products and reactants

The rate of the forward reaction = rate of reverse

Reply 1394

TheBigGeek

9

Original post by airheadbuster

First one is correct.

>Cl atom is too big.

It will be the electronegativity difference between CL and H is not high enough to make hydrogen sufficiently &+. So, there will be no hydrogen bonding in HCl which means it will have lower boiling point.

Features of dynamic equilibrium:

1. The rate of forward reaction is equal to the rate of backward reaction.
2. The concentration of the species on both sides of the reaction will be unchanged.

IR:

They absorb IR emitted from Earth's surface and re-radiates it back to Earth, contributing to global warming.

Your "features of dynamic equilibrium" seems better than mine!
And our teacher specifically said that the Cl atoms can't H bond because of its size...

Reply 1395

airheadbuster

2

Original post by Goods

I did an sn1 mechanism I'm not sure if it should have been sn2 it was a secondary haloalkanes :I

Posted from TSR Mobile

I did SN1 too and I think we are right. They said "show the transfer of electrons with curly arrows" which probably meant heterolytic fission in C-Cl bond. :smile:

Reply 1396

GCSE-help

6

I think it was a tricky paper, especially the multiple choice but i think i went well for me (fingers crossed). I'm sure you all on here did fine too :biggrin:

I know I lost 2 silly marks for sure, I put flame test for the second part of the testing question even though it asked to avoid using heat *doh*. But I swear all the questions were 1or 2 markers apart from the last one? :angry:

Reply 1397

Goods

16

Original post by TheBigGeek

Do we want to start an unofficial markscheme? Disagree with me where you feel differently!

I'm pretty sure the thiosulphate calculations went like this:
=0.00116
=0.00058
=0.0125
=0.01192
=13.8%

And I think the percent error was 0.86%...

The question with the mechanism was:
=The solution would be dissolved in ethanol
=It was elimination
=The solution would be dissolved in water
=It was the Sn2 mechanism

The first section 2 question was Ba(s) + 2H2O (l) ---> Ba(OH)2 (aq) + H2 (g)
The Ba changed oxidation number from 0 to +2
And the H changed from +1 to 0 (though it stayed the same in the hydroxide)

Then it was Ba(OH)2 + 2HCL ---> BaCl2 + 2H2O

The difference would a white precipitate
Because Barium sulphate is insoluble and Barium hydroxide is extremely soluble.

Bonding questions:
18 electrons
London forces
Both have London forces, though the one that's not F2 has permanent dipoles
HF has hydrogen bonding, which is the strongest intermolecular force
The Cl atom in HCl is too big to H bond, so doesn't form H bonds, so won't have the highest boiling point

Questions following the little article
(This one I'm totally not sure about!) It came out as 2200ppm, and 2200 > 60 so richer in bromine.
More carbonate ions, less CO2, as more hydrogen carbonate ions were produced to use up the excess carbonate.
Mechanism for global warming (what are the marks for here?!): Molecules with polar bond absorb IR which means that the Sun's rays are trapped in the atmosphere when they are reflected off the earth
Assorted bull**** for the last 4 marker.

The equilibria stuff
(Again, not sure about this one) The HCl donated H+ ions to the equilibrium mixture, moving the equilibrium to the left and meaning that more bromine is formed rather than hydrolysed
Temp increase it moved to the right because the forward reaction was endothermic and a temp increase favours the endothermic reaction
Features of dynamic equilibrium, I put (not sure about this):
-At a molecular level there is ceaseless change
-To the naked eye, there is no change in the solution

The multiple choice were (assorted answers, though as much in order as I can remember)
SF6
CCl4
2-chlorobutane
Potassium nitrate
Ozone depletion
A for the titration multiple choice question
The most common energy of the molecules

I'm pretty sure it was sn1 the other point with dynamic equilibrium is that concentrations of reactants are constant

Was the alternative test a flame test? It said not using acid or by heating... But a flame test uses both it was all I could think of ....

Posted from TSR Mobile

Reply 1398

GCSE-help

6

Original post by airheadbuster

I did SN1 too and I think we are right. They said "show the transfer of electrons with curly arrows" which probably meant heterolytic fission in C-Cl bond. :smile:

Doesn't the C-Cl bond break heterolytically in sn2 mechanism as well?