How was Chem P4? 9701/42

[Sadia Ahmad]

the grade boundary will definitely be low this time because the paper was tough

 

[Dark Destination]

the grade boundary will definitely be low this time because the paper was tough

I really hope so!

But like how much low do you think it'll be? Can it be like 30 out of 100 for A?

 

[Sean Tan]

I found the paper moderately hard, but i do understand why many said it's the hardest paper, due to the exposure of many unfamiliar questions.
These are the questions (i can't remember them exactly.. these are just guesses from fragments of my classmates' memory!)
The questions may not be in the correct order
1. Decomposition of Mg(NO3)2.6H20
This question was okay. Not too bad for a start. But i was a bit disappointed that they only gave 2 marking points for explanation of thermal stability.
Many were confused with the 4 marking point question (the explanation for the observation of decomposition), i guess not many knows that first water vapour will be given out First upon gentle heat.
Then, upon strong heating, NO2 gas as well as O2 gas will be released.
2. Acidities with pKa
I found this question very easy. Although many were confused with CH2ClCH3COOH and CH3CH2ClCOOH.
If the Cl atom is nearer to the COOH group, there is a stronger electron withdrawing effect. So, CH3CH2ClCOOH should be more acidic, as the Cl atom is CH2CH3COOH is further away from the COOH group.
3. Organic synthesis
I was so disappointed with the amount of organic questions in this paper!
Hmm this question for me was easy. The reactions require AS knowledge. acidic hydrolysis and etc. I cant rmbr which organic synthesis question was asked first, but i'm assuming that the one with the benzene (ibuprofen) is the 8th question.
4. KStability linked to entropy. This is where things start to become dreadful.
I have no comments about this question. It is a new syllabus after all. The delta S calculation was okay (just sub in the values, i remember it being positive)
The dilute by a factor of 1000 question was tricky. Not many knew how to do that. Even lecturers (yes, I've confirmed that)
5. Pt(NH3)2Cl2 question, cis platin.
many knew that geometrical isomerism exists in this complex, but did not know how to draw it
(You MUST include the wedges!)
The stereochemistry for the 2nd question is probably tetrahedral, because question says that it does not have isomers.
6. Enzyme, Basicities and buffers
er.... no comment about this question. the pH calculation was straightfoward (with Ka given).
I guess many complained about the enzymes, but it is actually still in the syllabus. (Check the AS syllabus of rates of reaction)
But i do understand why many complained about that. I didn't expect that question to come out either.
I think many were confused with the equation of buffer using CH3NH2.
This is what i wrote:
CH3NH2 + H+ ---> CH3NH3+
CH3NH3+ + OH- ----> CH3NH2 + H2O
I'm not very sure about my answer.
7. Electrophoresis and infrared
The apparatus set up for electrophoresis was asked before in past years with clear mark scheme.
The best pH to distinguish between 3 sets of pairs of amino acids.... Bad marking point allocation..
3 marks, for checking the data booklet and writing explanations, For Each. CIE why??
The infrared question was okay. just look at data booklet and bam. But some were confused with the O-H and N-H bond.
8. Organic synthesis and Carbon NMR
If i'm not mistaken, Many students ( I mean many) missed out the question which requires you to find the number of chiral carbon atoms.
This question asked about the synthesis of ibuprofen, and yes, AS organics is heavy here, including HCN + trace amounts of NaCN + dil.H2So4
Many forgot that tertiary alcohols can be dehydrated to form alkenes.
the Carbon NMR was pretty straightforward. You should quote the ppm values from the tables given above.
The left isomer should be isomer B, the right should be A.
To distinguish those two, i suggested hydrolysing them, and adding Br2(aq), as one of the isomers will produce a phenol when hydrolysed.
Many suggested tri-iodomethane test, i am unsure if this is acceptable.
9. Lattice energy and Hess' Cycle
The explanation for the solubility of hydroxides should be the complete opposite for sulfates.
What happens when the reaction using HCl is replaced with HNO3...
i wrote fairly similar values. This is because both are strong acids, and both ionises strongly to form the H+ ions required for the reaction below (the one with Ca solid)
Many wrote about the polarisation of NO3- ion, however NO3- ions are acting as spectator ions. they are not involved in the main equation.
I got the answer for the Hess' Cycle to be -534 kJ mol-1. The reaction is very reactive, so i guess i got the correct answer.
Many obtained 2000++ kJmol-1. This is because they left out the IE of Hydrogen (yes, hydrogen atoms can be ionized)

Ca(s) + 2H+ (aq) ---> Ca2+ (aq) + H2(g)
They gave hydration of Ca2+ aq and 2H+ aq
They also gave atomisation of Ca(s).


First, atomise the Ca(s) to Ca(g)
Then, ionise Ca(g) to Ca2+ (g).
You can then connect Ca2+(g) to Ca2+(aq) , this is hydration.

Next, atomise the H2 gas to form 2H(g), you can use Bond Energy value for H-H.
Then, ionise the 2H(g) to form 2H+(g) , in this case, it is 2x(IE of H) many missed out this step
You can then connect 2H+(g) to 2H+(aq), this is hydration.

It's hard for me to draw the cycle here.. but you should put Ca2+ (g) and 2H+(g) as the intermediates.

10. Splitting of d-orbitals (Fe3+ ion) and Kstability question relating to colours
Not sure if they are the same question.
The Fe3+ ion question's answer should be
I I I I

I __ __
Note that they bolded the word This Fe3+ ion.
The Fe3+ ion has probably formed dative covalent bonds with ligands.
This causes 2 electrons to be promoted to a higher orbital
(2 electrons because they hinted that there is only 1 unpaired d-orbital)

The last page of the paper... Kstability and colour
The higher the Kstab, the easier it is for the complex to be formed.
if im not mistaken, the first answer is
violet to deep red to colourless
2nd answer is
violet to colourless, and remains that way.
KStability for the complex which is colourless is higher than the one which is deep red.

And of course, the type of reaction is ligand exchange.


Good luck.
And if you ask me to predict the grade threshold for this paper, i'd say 55-62.
I've done all the past years for chemistry P4, 2002 - 2015.
I've analysed each paper thoroughly, including examiner reports and grade thresholds (average is 60+)
Due to the exposure of many unfamiliar questions, i guess my expected grade threshold is reasonable.

 

[farhan141]

So

I found the paper moderately hard, but i do understand why many said it's the hardest paper, due to the exposure of many unfamiliar questions.
These are the questions (i can't remember them exactly.. these are just guesses from fragments of my classmates' memory!)
The questions may not be in the correct order
1. Decomposition of Mg(NO3)2.6H20
This question was okay. Not too bad for a start. But i was a bit disappointed that they only gave 2 marking points for explanation of thermal stability.
Many were confused with the 4 marking point question (the explanation for the observation of decomposition), i guess not many knows that first water vapour will be given out First upon gentle heat.
Then, upon strong heating, NO2 gas as well as O2 gas will be released.
2. Acidities with pKa
I found this question very easy. Although many were confused with CH2ClCH3COOH and CH3CH2ClCOOH.
If the Cl atom is nearer to the COOH group, there is a stronger electron withdrawing effect. So, CH3CH2ClCOOH should be more acidic, as the Cl atom is CH2CH3COOH is further away from the COOH group.
3. Organic synthesis
I was so disappointed with the amount of organic questions in this paper!
Hmm this question for me was easy. The reactions require AS knowledge. acidic hydrolysis and etc. I cant rmbr which organic synthesis question was asked first, but i'm assuming that the one with the benzene (ibuprofen) is the 8th question.
4. KStability linked to entropy. This is where things start to become dreadful.
I have no comments about this question. It is a new syllabus after all. The delta S calculation was okay (just sub in the values, i remember it being positive)
The dilute by a factor of 1000 question was tricky. Not many knew how to do that. Even lecturers (yes, I've confirmed that)
5. Pt(NH3)2Cl2 question, cis platin.
many knew that geometrical isomerism exists in this complex, but did not know how to draw it
(You MUST include the wedges!)
The stereochemistry for the 2nd question is probably tetrahedral, because question says that it does not have isomers.
6. Enzyme, Basicities and buffers
er.... no comment about this question. the pH calculation was straightfoward (with Ka given).
I guess many complained about the enzymes, but it is actually still in the syllabus. (Check the AS syllabus of rates of reaction)
But i do understand why many complained about that. I didn't expect that question to come out either.
I think many were confused with the equation of buffer using CH3NH2.
This is what i wrote:
CH3NH2 + H+ ---> CH3NH3+
CH3NH3+ + OH- ----> CH3NH2 + H2O
I'm not very sure about my answer.
7. Electrophoresis and infrared
The apparatus set up for electrophoresis was asked before in past years with clear mark scheme.
The best pH to distinguish between 3 sets of pairs of amino acids.... Bad marking point allocation..
3 marks, for checking the data booklet and writing explanations, For Each. CIE why??
The infrared question was okay. just look at data booklet and bam. But some were confused with the O-H and N-H bond.
8. Organic synthesis and Carbon NMR
If i'm not mistaken, Many students ( I mean many) missed out the question which requires you to find the number of chiral carbon atoms.
This question asked about the synthesis of ibuprofen, and yes, AS organics is heavy here, including HCN + trace amounts of NaCN + dil.H2So4
Many forgot that tertiary alcohols can be dehydrated to form alkenes.
the Carbon NMR was pretty straightforward. You should quote the ppm values from the tables given above.
The left isomer should be isomer B, the right should be A.
To distinguish those two, i suggested hydrolysing them, and adding Br2(aq), as one of the isomers will produce a phenol when hydrolysed.
Many suggested tri-iodomethane test, i am unsure if this is acceptable.
9. Lattice energy and Hess' Cycle
The explanation for the solubility of hydroxides should be the complete opposite for sulfates.
What happens when the reaction using HCl is replaced with HNO3...
i wrote fairly similar values. This is because both are strong acids, and both ionises strongly to form the H+ ions required for the reaction below (the one with Ca solid)
Many wrote about the polarisation of NO3- ion, however NO3- ions are acting as spectator ions. they are not involved in the main equation.
I got the answer for the Hess' Cycle to be -534 kJ mol-1. The reaction is very reactive, so i guess i got the correct answer.
Many obtained 2000++ kJmol-1. This is because they left out the IE of Hydrogen (yes, hydrogen atoms can be ionized)

Ca(s) + 2H+ (aq) ---> Ca2+ (aq) + H2(g)
They gave hydration of Ca2+ aq and 2H+ aq
They also gave atomisation of Ca(s).


First, atomise the Ca(s) to Ca(g)
Then, ionise Ca(g) to Ca2+ (g).
You can then connect Ca2+(g) to Ca2+(aq) , this is hydration.

Next, atomise the H2 gas to form 2H(g), you can use Bond Energy value for H-H.
Then, ionise the 2H(g) to form 2H+(g) , in this case, it is 2x(IE of H) many missed out this step
You can then connect 2H+(g) to 2H+(aq), this is hydration.

It's hard for me to draw the cycle here.. but you should put Ca2+ (g) and 2H+(g) as the intermediates.

10. Splitting of d-orbitals (Fe3+ ion) and Kstability question relating to colours
Not sure if they are the same question.
The Fe3+ ion question's answer should be
I I I I

I __ __
Note that they bolded the word This Fe3+ ion.
The Fe3+ ion has probably formed dative covalent bonds with ligands.
This causes 2 electrons to be promoted to a higher orbital
(2 electrons because they hinted that there is only 1 unpaired d-orbital)

The last page of the paper... Kstability and colour
The higher the Kstab, the easier it is for the complex to be formed.
if im not mistaken, the first answer is
violet to deep red to colourless
2nd answer is
violet to colourless, and remains that way.
KStability for the complex which is colourless is higher than the one which is deep red.

And of course, the type of reaction is ligand exchange.


Good luck.
And if you ask me to predict the grade threshold for this paper, i'd say 48-55.
I've done all the past years for chemistry P4, 2002 - 2015.
I've analysed each paper thoroughly, including examiner reports and grade thresholds (average is 60+)
Due to the exposure of many unfamiliar questions, i guess my expected grade threshold is reasonable.

So if A is at 50 ish how much can we expect E to be at

 

[Sean Tan]

20-25 for E i presume. Average is 29 (roughly)
my prediction is of course, just a prediction.
It may be lower , it may be higher.
But i can assure you its not more than 29.

 

[asadalam]

So out of 260, where do you think A and A* will be at?
And tell your prediction for Maths too out of 250...

A* would prolly be at 170-190 Imo,and maths would be 220-235.

 

[Hashimm]

I found the paper moderately hard, but i do understand why many said it's the hardest paper, due to the exposure of many unfamiliar questions.
...

This is very useful, thank you! So I suppose the grade thresholds will probably be high 50s, even low 60s at a stretch. Does this sound about right to you? I can see A LOT of marks being dropped in a few places.

 

[farhan141]

20-25 for E i presume. Average is 29 (roughly)
my prediction is of course, just a prediction.
It may be lower , it may be higher.
But i can assure you its not more than 29.

I hope I get a D or E. Just want to pass Chemistry

 

[Sean Tan]

This is very useful, thank you! So I suppose the grade thresholds will probably be high 50s, even low 60s at a stretch. Does this sound about right to you? I can see A LOT of marks being dropped in a few places.

Yes, that's about right. Don't worry, we'll get through it

 

[Sean Tan]

I hope I get a D or E. Just want to pass Chemistry

You will! Just believe in yourself

 

[Abdullah Zahid]

Trend for chem is in the 60's i think it will be around 60-65 lets see though

 

[Awesome12]

Threshold is calculated in following way!!

1. Add raw marks for P1,2,4 and P5
2. Multiply marks of P3 with 0.75
3. Add all marks and then whatever the score you will get is out of 260 and according to the threshold that is where you will be placed.

I doubt it is as easy as that. Dont you have to consider the paper weightages too.
Thus I think it is calculated as follows
Mark in p1 × 15
Mark in p2 × 23
Mark in p3 /40 should be converted to out of 30. Then that mark x 12
Mark in p4 x 38
Mark in p5 x 12

Add all of these marks and divide by 6500. Multiply by 100. You will get a percentage value.
You can kmow from the grade boundaries pdf about the percent required for a certain grade. Like for example if for an A*, it is 204/260 × 100 = 78.46%.
You then compare your percentage value to the above percent to find where do you lie and your correspomding grade.
Again that is how i think it is done.

I have gone through a few similar threads, and people have pointed out to your method. I am not sure which method is right, but one would point out saying that both methods produce nearly the same grade/ marks. That is true as long as you have a uniform mark distribution. For my method effing up in one big component (particularly p4) can produce disastrous effects whereas in your method the damage can be neutralized by achieving higher marks in the other components as the overall sum of marks is counted and not their respective weightages. Could you please confirm which method is the one actually used. I hope your method is right, lol.

 

[thandazani]

Lets hope and pray that the oct/nov session wont be as difficult as you guys say the may/june was..!!!!!!!

 

[muhammadali233]

Lets hope and pray that the oct/nov session wont be as difficult as you guys say the may/june was..!!!!!!!

That is just wishful thinking

 

[thandazani]

Well just wait for wishful thinking coming to reality......nigga!!!

 

[Sufiman]

I doubt it is as easy as that. Dont you have to consider the paper weightages too.
Thus I think it is calculated as follows
Mark in p1 × 15
Mark in p2 × 23
Mark in p3 /40 should be converted to out of 30. Then that mark x 12
Mark in p4 x 38
Mark in p5 x 12

Add all of these marks and divide by 6500. Multiply by 100. You will get a percentage value.
You can kmow from the grade boundaries pdf about the percent required for a certain grade. Like for example if for an A*, it is 204/260 × 100 = 78.46%.
You then compare your percentage value to the above percent to find where do you lie and your correspomding grade.
Again that is how i think it is done.

I have gone through a few similar threads, and people have pointed out to your method. I am not sure which method is right, but one would point out saying that both methods produce nearly the same grade/ marks. That is true as long as you have a uniform mark distribution. For my method effing up in one big component (particularly p4) can produce disastrous effects whereas in your method the damage can be neutralized by achieving higher marks in the other components as the overall sum of marks is counted and not their respective weightages. Could you please confirm which method is the one actually used. I hope your method is right, lol.

My method is perfectly legit because i have reffered to the CIE's official marking methods that they have emphasized upon themselves!! Your method yields the same result at a margin of .5% accuracy!!

Therefore its better using my method because it yields the same results in a simple and more explanatory way...

 

[Raja2396]

Guys chill out, tomorrow is result day. P4 9701 is usually 55-65 for A, never seen going below 53-55 for A and E is 23-25 mostly.

 

[afrolina]

I don't remember that question. ._.

I'm probably losing so many marks in paper 4! Probably like 50 or more.... *sigh*

same condition for physics as well