Edexcel Chemistry Unit 4 23rd January Watch

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jean7250
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I found it relatively alright except for a few questions ..

These are some of answers I can remember .

question 1 - fairly straight forward .
for SO2 + H20 = H2 SO3 = H+ + HSO3-

question 2 - last question : i said the + 2 state becomes more stable down the group so equation II was the better one .

question 3 - organic stuff . first question i put propanylchloride
the the stuff about reagent - ammonia , P4 O10

the last question about which will form acidic solution i put acid chlorids with water = carboxilic acid + HCL

and the next one which will for a basic solution i put the primary amine with water C2 H5 NH2 + H20 = C2 H5 NH3+ + OH-

question 4 (organic) was slightly wierd .

for the part about oxidising the Gly...compound to citral i put heat under reflux with K2 CR2 O7 + H2 SO4 . the aldehyde will be produced. then distill off the aldehyde so that we wont get the carboxylic acid....


for the structures with HBR, i just replaced the CHO (aldehyde group with CH2 BR and changed the structure to an alkane .. ( ithink)

with HCN i replaced the aldehyde group with CH2 OH CN

with gringard i replaced the aldehyde group with CH2 OH. (primary alcohol)

cant remember the rest ...

for the lattice enthalp of SR CL2 i got -25XX kjmol ( sorry cant remember the exact value)

then for the enthalpy of formation of SR CL i got - 255 kjmol ..

then for the Kp question there was no bottom line ...

so Kp = [....] X [.....] ( sorry cant rememeber the exact names of the stuff .. just made sure the solid state was not included.

the calculation for kp i i was bit confused because original mol and equilibrium mole values were not given .. so i just used an equilibrium value as 1 mol for each of the substance and got a total of 2 mol .. etc etc..

anyway i got a value of 4.11 atm2

then the graph i really screwed up .... i drew it the opposite way .. it chould have been drawn from a starting ph of 10 i think .. dont ask me why cause i dont know ... but thats what some of the other people did ... i started the graph at a ph of 1 and at 40 cm of HCL i put the vertical portion and the end of the graph was at about ph 10 ...

that's about all i can remember ...

aNYONE ELSE ??
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nodabooper
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(Original post by jean7250)
I found it relatively alright except for a few questions ..

These are some of answers I can remember .

question 1 - fairly straight forward .
for SO2 + H20 = H2 SO3 = H+ + HSO3-

question 2 - last question : i said the + 2 state becomes more stable down the group so equation II was the better one .

question 3 - organic stuff . first question i put propanylchloride
the the stuff about reagent - ammonia , P4 O10

the last question about which will form acidic solution i put acid chlorids with water = carboxilic acid + HCL

and the next one which will for a basic solution i put the primary amine with water C2 H5 NH2 + H20 = C2 H5 NH3+ + OH-

question 4 (organic) was slightly wierd .

for the part about oxidising the Gly...compound to citral i put heat under reflux with K2 CR2 O7 + H2 SO4 . the aldehyde will be produced. then distill off the aldehyde so that we wont get the carboxylic acid....


for the structures with HBR, i just replaced the CHO (aldehyde group with CH2 BR and changed the structure to an alkane .. ( ithink)

with HCN i replaced the aldehyde group with CH2 OH CN

with gringard i replaced the aldehyde group with CH2 OH. (primary alcohol)

cant remember the rest ...

for the lattice enthalp of SR CL2 i got -25XX kjmol ( sorry cant remember the exact value)

then for the enthalpy of formation of SR CL i got - 255 kjmol ..

then for the Kp question there was no bottom line ...

so Kp = [....] X [.....] ( sorry cant rememeber the exact names of the stuff .. just made sure the solid state was not included.

the calculation for kp i i was bit confused because original mol and equilibrium mole values were not given .. so i just used an equilibrium value as 1 mol for each of the substance and got a total of 2 mol .. etc etc..

anyway i got a value of 4.11 atm2

then the graph i really screwed up .... i drew it the opposite way .. it chould have been drawn from a starting ph of 10 i think .. dont ask me why cause i dont know ... but thats what some of the other people did ... i started the graph at a ph of 1 and at 40 cm of HCL i put the vertical portion and the end of the graph was at about ph 10 ...

that's about all i can remember ...

aNYONE ELSE ??





how come your one was different? do you follow the nuffield syllabus, or something else????
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matouwah
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****.....i forgot to mention midly oxidise for the alcohol to ketone....also i named the acid chloride wrong....i forgot to include the C attached to the functional group....i think for the addition of HBr to the compound...i think that it reacts with the double bond and not the functional group....
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hornblower
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(Original post by nodabooper)
how come your one was different? do you follow the nuffield syllabus, or something else????
We do the standard Edexcel syllabus.

There is also an Edexcel Nuffield syllabus.

J.
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The Best
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(Original post by jean7250)
I found it relatively alright except for a few questions ..

These are some of answers I can remember .

question 1 - fairly straight forward .
for SO2 + H20 = H2 SO3 = H+ + HSO3-

question 2 - last question : i said the + 2 state becomes more stable down the group so equation II was the better one .

question 3 - organic stuff . first question i put propanylchloride
the the stuff about reagent - ammonia , P4 O10

the last question about which will form acidic solution i put acid chlorids with water = carboxilic acid + HCL

and the next one which will for a basic solution i put the primary amine with water C2 H5 NH2 + H20 = C2 H5 NH3+ + OH-

question 4 (organic) was slightly wierd .

for the part about oxidising the Gly...compound to citral i put heat under reflux with K2 CR2 O7 + H2 SO4 . the aldehyde will be produced. then distill off the aldehyde so that we wont get the carboxylic acid....


for the structures with HBR, i just replaced the CHO (aldehyde group with CH2 BR and changed the structure to an alkane .. ( ithink)

with HCN i replaced the aldehyde group with CH2 OH CN

with gringard i replaced the aldehyde group with CH2 OH. (primary alcohol)

cant remember the rest ...

for the lattice enthalp of SR CL2 i got -25XX kjmol ( sorry cant remember the exact value)

then for the enthalpy of formation of SR CL i got - 255 kjmol ..

then for the Kp question there was no bottom line ...

so Kp = [....] X [.....] ( sorry cant rememeber the exact names of the stuff .. just made sure the solid state was not included.

the calculation for kp i i was bit confused because original mol and equilibrium mole values were not given .. so i just used an equilibrium value as 1 mol for each of the substance and got a total of 2 mol .. etc etc..

anyway i got a value of 4.11 atm2

then the graph i really screwed up .... i drew it the opposite way .. it chould have been drawn from a starting ph of 10 i think .. dont ask me why cause i dont know ... but thats what some of the other people did ... i started the graph at a ph of 1 and at 40 cm of HCL i put the vertical portion and the end of the graph was at about ph 10 ...

that's about all i can remember ...

aNYONE ELSE ??
Yes that Kp question was very strange. I'm sure there is some data missing, because they didnt give any moles or values at all?!!! But i did exactly like u! I'm sure there's a mistake in the question.
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FunkyTeenAngel
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i hated the buffer calculation question, and for SO2, werent the equations meant to be ionic?
as for the Kp - i just took them as 'x' basically my answer was 4.21 or somin.
i think it was prolly the hardet chem test iv done, how bout u guys?.

and for the ph>7 , i chose the nitrile... RNH2 + H2O + NaOH = cant remember
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hornblower
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(Original post by The Best)
Yes that Kp question was very strange. I'm sure there is some data missing, because they didnt give any moles or values at all?!!! But i did exactly like u! I'm sure there's a mistake in the question.
Yeah - that question was nasty. I was looking for some more information! I guessed and got 4.41 atm^2.

Question 1 didn't go well at all - those ionic equations I just didn't learn but knew I had to!

Everyone I know had trouble with those questions especially.

Thank God for UMS!

J.
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matouwah
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what do u reckon u will need outta 75 for an A?
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FunkyTeenAngel
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(Original post by hornblower)
Yeah - that question was nasty. I was looking for some more information! I guessed and got 4.41 atm^2.

Question 1 didn't go well at all - those ionic equations I just didn't learn but knew I had to!

Everyone I know had trouble with those questions especially.

Thank God for UMS!

J.
o yeh i got 4.41 i think.. 4.21/4.22 was the total atm

i found teh alumnium equations alrite but id never seen an ionic equation for SO2

btw i think u have to get at least 72-75% for an A so i think thats bout 60 marks.. but im not sure.. im not too good at mental maths

btw whats UMS...
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matouwah
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(Original post by FunkyTeenAngel)
o yeh i got 4.41 i think.. 4.21/4.22 was the total atm

i found teh alumnium equations alrite but id never seen an ionic equation for SO2

btw i think u have to get at least 72-75% for an A so i think thats bout 60 marks.. but im not sure.. im not too good at mental maths

btw whats UMS...
UMS is uniform marking scale or something like dat.....if u get 70% in the test....it might be moved up by UMS according to the average and how hard ppl found it.....i think UMS can only scale up your grade....never down...
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FunkyTeenAngel
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(Original post by matouwah)
UMS is uniform marking scale or something like dat.....if u get 70% in the test....it might be moved up by UMS according to the average and how hard ppl found it.....i think UMS can only scale up your grade....never down...
well i think most ppl found the test quite hard relative to the other past papers so maybe the grade boundary for an A will be lowered. fingers crossed.
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hornblower
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(Original post by matouwah)
UMS is uniform marking scale or something like dat.....if u get 70% in the test....it might be moved up by UMS according to the average and how hard ppl found it.....i think UMS can only scale up your grade....never down...
UMS is the method by which examiners determine grades. Raw marks are converted to Uniform Marking Scale points using some very complex mathematics - some Jedi formulae or something. This is due to the variation in difficulty and performance in papers.

The relationship between raw marks and UMS points is not linear - the graph would look like a giraffe, not a straight line. Thus, the distribution of grades is shifted towards both extremes - A's and U's. This means that if you're in the middle, say C-D, then a few marks can make a lot of difference.

UMS marks are usually scaled up, and it is possible to get full UMS points without getting a hundred percent in a module (which I've done twice). It is possible for them to be scaled down - it has definitely been done before, but I can't remember the exact details.

J.
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FunkyTeenAngel
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^ so i guess thats a good thing rite??
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hornblower
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(Original post by FunkyTeenAngel)
^ so i guess thats a good thing rite??
Yes. Relax!

J.
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FunkyTeenAngel
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(Original post by hornblower)
Yes. Relax!

J.

lol!!! i will
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jean7250
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How did you guys find the graph for the titration question ? the one with 4 marks ... these edexcel examiners are always finding way to confuse and make us loose marks .. in most of the past papers, any titation graphs were with volume of alkali added .. this is the first graph i have see asking us to draw with volume of acid added .. so the whole stupid graph is the opoposite way from what we normally draw ... damn .. that's another 4 marks gone!!
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MalaysianDude
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well i didnt find any difficulty at sctching the graph
cause the ph of the original alkali was given as 11.13
the excess acid should have been about pH 1
the end point should be about 20cm³
all of these willl give you the full 4 points
but then again the kp question was tricky cause of the (s) symbol..
if i saw it then i would have been able to answer it cause one of the elements was a solid and the pressure of solids was not counted

and yeah,about jean`s answer of H2SO3
didnt they want the ionic equation for S02 and H+
cause they asked you to show the acid properties
that means that S02 would have donated H+ ions or in other words,reduce what ever it comes in contact with

i hated the buffer calculation question, and for SO2, werent the equations meant to be ionic?
agreed....that is why....
i stated that:
S02 + 2OH- ---> H2SO3 + H20
cause SO2 donates H+ ions since OH ions were reduced to H20
the product would be H2SO3
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matouwah
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(Original post by hornblower)
UMS is the method by which examiners determine grades. Raw marks are converted to Uniform Marking Scale points using some very complex mathematics - some Jedi formulae or something. This is due to the variation in difficulty and performance in papers.

The relationship between raw marks and UMS points is not linear - the graph would look like a giraffe, not a straight line. Thus, the distribution of grades is shifted towards both extremes - A's and U's. This means that if you're in the middle, say C-D, then a few marks can make a lot of difference.

UMS marks are usually scaled up, and it is possible to get full UMS points without getting a hundred percent in a module (which I've done twice). It is possible for them to be scaled down - it has definitely been done before, but I can't remember the exact details.

J.
scaled down??....but surely it would be unfair for someone who got 100% in the actual test to get lower than that in UMS marks.,..
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hornblower
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(Original post by matouwah)
scaled down??....but surely it would be unfair for someone who got 100% in the actual test to get lower than that in UMS marks.,..
I said before - the conversion of raw marks to UMS points is not linear. If you draw a graph of UMS points against raw marks, you would get a giraffe-shaped graph and not a straight line.

J.
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The Best
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In the first question (last part on the 1st page) it asked for the ionic equations for Aluminuim oxide and Sulphur oxide. The Al is ok, but i never knew that there is such thing as "Sulphur OXIDE" i thought it was Sulphur Dioxide/Trioxide????????????
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