OCR AS Salters Chemistry F332 - Wednesday 23rd May 2012 1:30pm
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Original post by TheStudent.
I thinkkkkkk it was about CFCs. The compound C,D,E stuff. Or that might have been later on. Can't remember 
i have a feeling it was question 3?! haha! i really can't remember!
question 1: was all about electrophillic addition - oxidation of alcohols etc
question 2: ???? - was it the titration malarky and bromide ions with chlorine??
question 3: CFC's?
question 4: equilibrium question - rate/ pressure etc
question 5: advanced notice
its really bugging me!
(edited 11 years ago)
Original post by dongonaeatu
no, you are wrong. I cant remember which was which, but the original compound was not secondary, it was tertiary and therefore cannot be oxidised and so no colour change. The other compound had a tertiary alcohol, but ALSO a primary alcohol, so it would be oxidised and so turn orange to green.
No, i meant the second compound is secondary.
Yehhhhh, so i thought because its got both a tertiary and a primary, it was therefore secondary overall.. to kind of meet them halfway.. lol...
Original post by swimming002
i have a feeling it was question 3?! haha! i really can't remember!
question 1: was all about electrophillic addition - oxidation of alcohols etc
question 2: ???? - was it the titration malarky and bromide ions with chlorine??
question 3: CFC's?
question 4: equilibrium question - rate/ pressure etc
question 5: advanced notice
its really bugging me!
question 1: was all about electrophillic addition - oxidation of alcohols etc
question 2: ???? - was it the titration malarky and bromide ions with chlorine??
question 3: CFC's?
question 4: equilibrium question - rate/ pressure etc
question 5: advanced notice
its really bugging me!
Wasn't the CFC's one 2nd and then the calculations questions were in question 3? With the halogens?
Original post by TheStudent.
No, i meant the second compound is secondary.
Yehhhhh, so i thought because its got both a tertiary and a primary, it was therefore secondary overall.. to kind of meet them halfway.. lol...
Yehhhhh, so i thought because its got both a tertiary and a primary, it was therefore secondary overall.. to kind of meet them halfway.. lol...
no, that is wrong.
Original post by swimming002
i have a feeling it was question 3?! haha! i really can't remember!
question 1: was all about electrophillic addition - oxidation of alcohols etc
question 2: ???? - was it the titration malarky and bromide ions with chlorine??
question 3: CFC's?
question 4: equilibrium question - rate/ pressure etc
question 5: advanced notice
its really bugging me!
question 1: was all about electrophillic addition - oxidation of alcohols etc
question 2: ???? - was it the titration malarky and bromide ions with chlorine??
question 3: CFC's?
question 4: equilibrium question - rate/ pressure etc
question 5: advanced notice
its really bugging me!
Im pretty sure there are five questions
With 1, 4 and 5 being in the right order.
Im not sure about questions 2 and 3. Its all a bit of a blur
but i know the questions were on CFCs, oxidation, and titration calculations.Original post by Beffnaay
Wasn't the CFC's one 2nd and then the calculations questions were in question 3? With the halogens?
possibly?! you're probably right!
Original post by TheStudent.
Im pretty sure there are five questions
With 1, 4 and 5 being in the right order.
Im not sure about questions 2 and 3. Its all a bit of a blur but i know the questions were on CFCs, oxidation, and titration calculations.
With 1, 4 and 5 being in the right order.
Im not sure about questions 2 and 3. Its all a bit of a blur
but i know the questions were on CFCs, oxidation, and titration calculations.There was the displacement reaction one but i can't really remember anything after that
Jeez, were there only 5 questions? I know they all have lots of parts, but that makes the paper sound so short :') You guys have jogged my memory, I'll edit and requote the thingy from my last post...
Original post by tasniaa
You think that's bad...
The January '12 paper for Bio had 'Plasmodium Vivax' written in big bold letters and the questions asked why it was written wrong. WHAT THE HE'LL IS THAT ABOUT?! Oh, and the answer was... That it wasn't italicsed.
The January '12 paper for Bio had 'Plasmodium Vivax' written in big bold letters and the questions asked why it was written wrong. WHAT THE HE'LL IS THAT ABOUT?! Oh, and the answer was... That it wasn't italicsed.
To be fair, you are supposed to know that. Also, vivax (species name) shouldn't be capitalised.
Original post by suncake
Jeez, were there only 5 questions? I know they all have lots of parts, but that makes the paper sound so short :') You guys have jogged my memory, I'll edit and requote the thingy from my last post...
Noooo there were so many sub-questions, and i think question 1 was the longest of them all.
Unofficial Mark Scheme
I can remember the majority of questions but I'm missing 4 marks... if anybody could tell me what questions I am missing that would be helpful.
Obviously this mark scheme is not going to be completely correct and the questions are not all in the correct order.
1. a) What are the functional groups present in the molecules? (2)
A. Alkene, ketone (carbonyl)
b) What is the molecular formula of the molecule? (2)
A. C15H22O
c) If bromine water is added, what will the colour change be? (2)
A. brown/red/orange to colourless
d) write the equation of the reaction will excess bromine water. Use the molecular formula from a) (2)
A. C15H220 + 2Br2 = C15H22O(Br2)2
e) What type of reaction is this? (2)
A. Electrophilic addition
g) Bromine reacts with Silver nitrate, what would the student see? (2)
A. cream precipitate
2. What type of alcohol does this molecule contain? (1)
A. Tertiary
b) Explain your answer (1)
A. The carbon atom to which the -OH group is attached is attached to three other carbon atoms.
c) What is the strongest bond that this molecule can form? (1)
A. I'm sure it's P.D - P.D as it contains -OH groups? Or is it H bonding?
d) Draw an OH radical, include the outer shell only. (1)
A. One 'dot' and 'cross' forming a bond between O and H
Then 5 more e- on the O, one on its own
e) What type of reaction produces the hydroxyl radical? (1)
A. Homolytic fission
f) Producing an alcohol from an alkene when water is added. State the reagents and conditions required. (2)
A. Phosphoric acid catalyst (allows sulphuric acid)
High temperatures and pressures / 300C and 60atm
g) Shows two compounds. A contained tertiary alcohols, B contained a primary alcohol. Describe the colour changes when potassium dichromate is added and explain this in terms of the types of alcohol. (5) (1 mark for QWC?)
A. A cannot be oxidised by potassium dichromate as it contains no H on the C atom to which the -OH group is attached.
Thus the colour will not change, it will remain orange
B can be oxidised as it is a primary alcohol and so does contain H atoms on the C to which the -OH group is attached
B will produce a colour change of orange to green and a carboxylic acid will be produced.
3. a) Name the compound CFl3CCl2H (2)
A. 2,2 - dichloro, 1,1,1 - trifluroethene (may ignore numbers)
b) Why is compound A less expensive? (1)
A. Some wrote that it contains no halogen atoms, and thus is less expensive to transport.
Others quoted a fact from the table provided
c) Why can this compound not be used as a cleaning agent (1)
A. Some wrote because it does not contain chlorine and so will not kill bacteria
Others quoted a fact from the table provided
d) Explain why CFCs are not broken down in the troposphere and explain how CFCs deplete ozone (5)
A. The C-F bond is too strong to be broken in the troposphere (1)
In the stratosphere the C-F bond breaks in the presence of high energy (1) UV radiation (1), by photo-dissociation (1?)
This forms Fluorine radicals (1)
Which catalyse ozone break down (1)
ii) Why is ozone a benefit? (3)
A. Ozone absorbs high energy (1) (can also quote specific v) UV radiation (1) which would cause skin cancer (1)
NOTE: mark schemes always say ignore skin DAMAGE
e) Label the partial charges on a CCl3F molecule (1)
A. delta positive on C, delta negative on all chlorine and fluorine atoms
g) explain what these partial charges are (2)
A. The partial charges show the differences in electronegativity values
Chlorine and Fluorine have a greater share of the e- and so have a partial negative charge
C has less of the share of electrons and so has a partial positive charge
h) Draw the 3-D shape of the molecule. (1)
A. Should include a tetrahedral shape with a wedge and a dotted line
i) based on g and h, is this molecule polar? (2)
A. This molecule is polar as fluorine is the most electronegative and so has a greater share of electrons producing a dipole
OR can be that all halogens are more electronegative
j) What are the oxidation states of Sulphur and was it Oxygen? (3)
Sulphur was 0 to +4 i think?
k) what is the formula of the reducing agent? (2)
S as it is itself oxidised and reduces oxygen
l) Name one agricultural source of methane (1)
A. Rice paddies/cattle farming/ mark scheme will include varied options
m) explain how increased conc. of methane are linked to global warming (2)
A. More methane molecules means more IR is absorbed (1) which increases the kinetic energy of the molecules and thus the temperature is increased (1)
4. Explain dynamic equilibrium (2)
A. Rate of forward reaction equals rate of reverse reaction (1) in a closed system/ conc. of reactants and products stay the same (1)
b) Why use nano something or other (2)
A. Provides a larger surface area for reacting particles to react. Thus there will be more frequent collisions, increasing the ROR
c) What is activation enthalpy (2)
A. The minimum energy required for colliding particles to react successfully. The energy needed to overcome the activation enthalpy barrier etc.
d) Effect of increased pressure on rate of reaction (3)
A. Increasing the pressure means the reacting particles are in closer proximity to each other. There will be more collisions. The rate of reaction will increase
e) Increased pressure on yield (3)
A. Position of equilibrium will shift to the .... (what side it was) / side with fewest gas molecules. So there will be increase/decrease in yield
e) Increased temperature on yield (3)
A. POE will shift to the right as the reaction favours the endothermic reaction.So the yield of products will increase
f) How many more times abundant is oxygen compared to methane? (2)
A. Oxygen was 21% methane was 0.00018%
So 20.9?
NOT SURE ABOUT THESE ANSWERS:
5. what is an addition polymer? give an example from the article but not poly(ethene) (3)
A. Many different answers...
I wrote along the lines of.... a large chain made up of many monomers added together
Could of included any polymer from the article, e.g. poly(propene)
b) Infrared spectroscopy (4)
I believe you had to discuss how the bonds absorb specific frequencies of IR
c) what would the people expect if reaction 2.1 had occurred? (2)
I believe you had to quote the absorptions of the functional groups
d) What is an initiation reaction? (1)
A. Produces radicals. There are no radicals at the start of this stage but there are at the end of the stage
e) What does a single headed arrow show? (1)
A. The movement of one electron
g) What type of reaction was the last radical reaction (1)
A. Termination
h) The I.B's question. How they are formed, how the structure link to strength of I.Bs (7)
A. Electrons are constantly moving (1)
This creates an uneven distribution of charge(1)
This creates an instantaneous dipole (1?)
Which induces a dipole in a neighbouring molecule (1)
The two are then attracted (1)
HDPE is un-branched and so has a larger molecular surface area (1)
The chains can pack more closely resulting in stronger I.Bs as they are closer together (1)
Thus, HDPE can whithstand more force than LDPE as it takes more energy to break the bonds (1)
Can also explain LDPE instead of HDPE
NOTE: There are alternative answers to the ones I have wrote, I just cba to include them all. You can use past mark schemes to mark your answers using these questions. There was 5 marks on titration's and 5 marks on E=hv also, i have not included these as i cannot remember the exact figures.
I can remember the majority of questions but I'm missing 4 marks... if anybody could tell me what questions I am missing that would be helpful.
Obviously this mark scheme is not going to be completely correct and the questions are not all in the correct order.
1. a) What are the functional groups present in the molecules? (2)
A. Alkene, ketone (carbonyl)
b) What is the molecular formula of the molecule? (2)
A. C15H22O
c) If bromine water is added, what will the colour change be? (2)
A. brown/red/orange to colourless
d) write the equation of the reaction will excess bromine water. Use the molecular formula from a) (2)
A. C15H220 + 2Br2 = C15H22O(Br2)2
e) What type of reaction is this? (2)
A. Electrophilic addition
g) Bromine reacts with Silver nitrate, what would the student see? (2)
A. cream precipitate
2. What type of alcohol does this molecule contain? (1)
A. Tertiary
b) Explain your answer (1)
A. The carbon atom to which the -OH group is attached is attached to three other carbon atoms.
c) What is the strongest bond that this molecule can form? (1)
A. I'm sure it's P.D - P.D as it contains -OH groups? Or is it H bonding?
d) Draw an OH radical, include the outer shell only. (1)
A. One 'dot' and 'cross' forming a bond between O and H
Then 5 more e- on the O, one on its own
e) What type of reaction produces the hydroxyl radical? (1)
A. Homolytic fission
f) Producing an alcohol from an alkene when water is added. State the reagents and conditions required. (2)
A. Phosphoric acid catalyst (allows sulphuric acid)
High temperatures and pressures / 300C and 60atm
g) Shows two compounds. A contained tertiary alcohols, B contained a primary alcohol. Describe the colour changes when potassium dichromate is added and explain this in terms of the types of alcohol. (5) (1 mark for QWC?)
A. A cannot be oxidised by potassium dichromate as it contains no H on the C atom to which the -OH group is attached.
Thus the colour will not change, it will remain orange
B can be oxidised as it is a primary alcohol and so does contain H atoms on the C to which the -OH group is attached
B will produce a colour change of orange to green and a carboxylic acid will be produced.
3. a) Name the compound CFl3CCl2H (2)
A. 2,2 - dichloro, 1,1,1 - trifluroethene (may ignore numbers)
b) Why is compound A less expensive? (1)
A. Some wrote that it contains no halogen atoms, and thus is less expensive to transport.
Others quoted a fact from the table provided
c) Why can this compound not be used as a cleaning agent (1)
A. Some wrote because it does not contain chlorine and so will not kill bacteria
Others quoted a fact from the table provided
d) Explain why CFCs are not broken down in the troposphere and explain how CFCs deplete ozone (5)
A. The C-F bond is too strong to be broken in the troposphere (1)
In the stratosphere the C-F bond breaks in the presence of high energy (1) UV radiation (1), by photo-dissociation (1?)
This forms Fluorine radicals (1)
Which catalyse ozone break down (1)
ii) Why is ozone a benefit? (3)
A. Ozone absorbs high energy (1) (can also quote specific v) UV radiation (1) which would cause skin cancer (1)
NOTE: mark schemes always say ignore skin DAMAGE
e) Label the partial charges on a CCl3F molecule (1)
A. delta positive on C, delta negative on all chlorine and fluorine atoms
g) explain what these partial charges are (2)
A. The partial charges show the differences in electronegativity values
Chlorine and Fluorine have a greater share of the e- and so have a partial negative charge
C has less of the share of electrons and so has a partial positive charge
h) Draw the 3-D shape of the molecule. (1)
A. Should include a tetrahedral shape with a wedge and a dotted line
i) based on g and h, is this molecule polar? (2)
A. This molecule is polar as fluorine is the most electronegative and so has a greater share of electrons producing a dipole
OR can be that all halogens are more electronegative
j) What are the oxidation states of Sulphur and was it Oxygen? (3)
Sulphur was 0 to +4 i think?
k) what is the formula of the reducing agent? (2)
S as it is itself oxidised and reduces oxygen
l) Name one agricultural source of methane (1)
A. Rice paddies/cattle farming/ mark scheme will include varied options
m) explain how increased conc. of methane are linked to global warming (2)
A. More methane molecules means more IR is absorbed (1) which increases the kinetic energy of the molecules and thus the temperature is increased (1)
4. Explain dynamic equilibrium (2)
A. Rate of forward reaction equals rate of reverse reaction (1) in a closed system/ conc. of reactants and products stay the same (1)
b) Why use nano something or other (2)
A. Provides a larger surface area for reacting particles to react. Thus there will be more frequent collisions, increasing the ROR
c) What is activation enthalpy (2)
A. The minimum energy required for colliding particles to react successfully. The energy needed to overcome the activation enthalpy barrier etc.
d) Effect of increased pressure on rate of reaction (3)
A. Increasing the pressure means the reacting particles are in closer proximity to each other. There will be more collisions. The rate of reaction will increase
e) Increased pressure on yield (3)
A. Position of equilibrium will shift to the .... (what side it was) / side with fewest gas molecules. So there will be increase/decrease in yield
e) Increased temperature on yield (3)
A. POE will shift to the right as the reaction favours the endothermic reaction.So the yield of products will increase
f) How many more times abundant is oxygen compared to methane? (2)
A. Oxygen was 21% methane was 0.00018%
So 20.9?
NOT SURE ABOUT THESE ANSWERS:
5. what is an addition polymer? give an example from the article but not poly(ethene) (3)
A. Many different answers...
I wrote along the lines of.... a large chain made up of many monomers added together
Could of included any polymer from the article, e.g. poly(propene)
b) Infrared spectroscopy (4)
I believe you had to discuss how the bonds absorb specific frequencies of IR
c) what would the people expect if reaction 2.1 had occurred? (2)
I believe you had to quote the absorptions of the functional groups
d) What is an initiation reaction? (1)
A. Produces radicals. There are no radicals at the start of this stage but there are at the end of the stage
e) What does a single headed arrow show? (1)
A. The movement of one electron
g) What type of reaction was the last radical reaction (1)
A. Termination
h) The I.B's question. How they are formed, how the structure link to strength of I.Bs (7)
A. Electrons are constantly moving (1)
This creates an uneven distribution of charge(1)
This creates an instantaneous dipole (1?)
Which induces a dipole in a neighbouring molecule (1)
The two are then attracted (1)
HDPE is un-branched and so has a larger molecular surface area (1)
The chains can pack more closely resulting in stronger I.Bs as they are closer together (1)
Thus, HDPE can whithstand more force than LDPE as it takes more energy to break the bonds (1)
Can also explain LDPE instead of HDPE
NOTE: There are alternative answers to the ones I have wrote, I just cba to include them all. You can use past mark schemes to mark your answers using these questions. There was 5 marks on titration's and 5 marks on E=hv also, i have not included these as i cannot remember the exact figures.
(edited 11 years ago)
The whole paper was so good. Just question one really messed it up for me! Might just be me being dumb but did anyone else find question 1 the hardest?
Anyways, ima go to bed and put this behind me can't change anything right now. But i think i gave it my best shot.
Good luck guys! focus on the exams you've got in the next couple of days
can't change anything right now. But i think i gave it my best shot.Good luck guys! focus on the exams you've got in the next couple of days
Does anyone know the what the grade boundaries are usually for an A on this exam are, it's just that I can see them being raised so i'm wondering how many marks roughly I can drop.
Original post by Beffnaay
The whole paper was so good. Just question one really messed it up for me! Might just be me being dumb but did anyone else find question 1 the hardest?
Yes! The additional material was the easiest. I was thinking, are they having a laugh lol.
Original post by TheStudent.
Anyways, ima go to bed and put this behind me can't change anything right now. But i think i gave it my best shot.
Good luck guys! focus on the exams you've got in the next couple of days
can't change anything right now. But i think i gave it my best shot.Good luck guys! focus on the exams you've got in the next couple of days
haha aww <3
good luck and good night xx
what did everyone write for the question about picking out a termination reaction from the advance notice? I didn't understand whether they wanted us to copy the reaction with the 'm' and 'n' or what ? so i just copied it. I have a feeling that that's wrong though. ??
I'm so glad someone agrees. After the 1st question I was thinking the rest would be even harder but I was pleasantly surprised Still did pretty awful in question 1 though, oops.
Still did pretty awful in question 1 though, oops.Original post by thegreenchildren
what did everyone write for the question about picking out a termination reaction from the advance notice? I didn't understand whether they wanted us to copy the reaction with the 'm' and 'n' or what ? so i just copied it. I have a feeling that that's wrong though. ??
no, thats what i did. copied the one with the radicals on the reactants and no radicals on the products.
@Alevelstudent1908 - you have good memory! In question 1 though, everyone's saying it was "bromine water" but I only remember it saying "bromine"... does it make a difference?
Same, I literally copied exactly what it said on the sheet, ie. "Ra(CH2)m + (CH2)nRa --->" etc... No idea if that's right!
Original post by thegreenchildren
what did everyone write for the question about picking out a termination reaction from the advance notice? I didn't understand whether they wanted us to copy the reaction with the 'm' and 'n' or what ? so i just copied it. I have a feeling that that's wrong though. ??
Same, I literally copied exactly what it said on the sheet, ie. "Ra(CH2)m + (CH2)nRa --->" etc... No idea if that's right!
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