AQA Chemistry Unit 2 (resit) CHEM2 10th June
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Original post by lahigueraxxx
crap I don't think we needed the H+! I added that in too! but the electrons should have balanced and therefore they would have cancelled out
I can remember from a past paper in a question they give you the overall equation and it includes h+ and i- i dont think we will lose a mark for not joining them together.
Original post by WhoDaresWins
yeah we got it wrong, it was white flame and white ppt 
We probs got 1 mark for white ppt
We probs got 1 mark for white ppt
Solid not ppt because it's not from solution
Questions I can remember:
Magnesium observations were bright white flame and white solid.
simple magnesium and steam equation
MBD graph was displaced to the right with a lower peak.
Decreased pressure increases yield as right side has fewer moles so the equilibrium will shift to the right to oppose the increase in pressure blah blah.
Using 300degrees will keep the rate high whilst keeping the yield high. If temps above 300 were used the equilibrium will shift to the left (endothermic direction) to oppose the increase in temp since the forward reaction is exothermic.
Enthalpy of combustion is the enthalpy change for one mole of a compound to burn completely in oxygen with all reactants and products in standard states
A was butan-2-ol and B was butan-1-ol due to silver mirror etc
T was carboxylic acid and S was aldehyde i think
(Z)-pent-2-ene and (E)-Pent-2-ene I think they were. Geometrical isomers formed due to restricted rotation about the C=C bond.
For mechanism of 2 different reactions the reagent was KOH/NaOH and the conditions were ethanolic and heat under reflux for one and aqueous for the other, i think that what i put. The reagent acted as a base in one and electrophile in the other.
The free-radical substitution question was easy plus the CClF3 was split into two species with a free radical on each.
for the question about why it is dangerous to acidify the solution of nacl and naclo or whatever, i put that when increasing the conc of H+ ions the equilibrium will shift to the left and the conc/moles of Chlorine gas will increase and chlorine gas is toxic in high concs
For the Mg and Ba question where the two solutions mix i said BaSO4 is insoluble and a white ppt would form and MgSO4 is soluble so no ppt would form.
Ba2+ + SO42- -> BaSO4
H2SO4 + 8H+ + 8e- -> H2S + 4H2O (i think H2s was the desired product... i dont even rememebr lol)
2I- -> I2 + 2e-
I wont list the advantages and disadvantages of fermentation, they'll have a range of options
when it asked about wanting to form one product to form over another or something it was KOH/NaOH and alcoholic
an answer for one of the questions about different intermediates forming was that it formed via the secondary carbocation which is more stable than a primary carbocation
The two environmental reasons were no SO2 produced which causes acid rain and the other is no CO2 produced which is a greenhouse gas. The economic reason was that scrap iron is cheap.
Cu2+ (aq) + Fe (s) -> Cu(s) + Fe2+ (aq) i think i put, cant remember
TiO2 + 2Cl2 + 2C -> TiCl4 + 2CO
TiCl4 + 2Mg -> 2MgCl2 + Ti
TiO cannot be extracted using carbon as titanium carbide is formed which is brittle.
ZnS + 1 1/2O2 -> ZnO + SO2
I think i got enthalpy of formation for the first one as low -300 or sumthin, i cant remember so feel free to correct me, It wasnt -1000 like others said as it was calculated from enthalpy of combustion data so u do reactants-products and not the usual products-reactants. The C-C bond i think was 300 and sumthin, i dont remember.
That's all i can remember for now, sorry for the vague questions and answers but hopefully it should help some ppl
Magnesium observations were bright white flame and white solid.
simple magnesium and steam equation
MBD graph was displaced to the right with a lower peak.
Decreased pressure increases yield as right side has fewer moles so the equilibrium will shift to the right to oppose the increase in pressure blah blah.
Using 300degrees will keep the rate high whilst keeping the yield high. If temps above 300 were used the equilibrium will shift to the left (endothermic direction) to oppose the increase in temp since the forward reaction is exothermic.
Enthalpy of combustion is the enthalpy change for one mole of a compound to burn completely in oxygen with all reactants and products in standard states
A was butan-2-ol and B was butan-1-ol due to silver mirror etc
T was carboxylic acid and S was aldehyde i think
(Z)-pent-2-ene and (E)-Pent-2-ene I think they were. Geometrical isomers formed due to restricted rotation about the C=C bond.
For mechanism of 2 different reactions the reagent was KOH/NaOH and the conditions were ethanolic and heat under reflux for one and aqueous for the other, i think that what i put. The reagent acted as a base in one and electrophile in the other.
The free-radical substitution question was easy plus the CClF3 was split into two species with a free radical on each.
for the question about why it is dangerous to acidify the solution of nacl and naclo or whatever, i put that when increasing the conc of H+ ions the equilibrium will shift to the left and the conc/moles of Chlorine gas will increase and chlorine gas is toxic in high concs
For the Mg and Ba question where the two solutions mix i said BaSO4 is insoluble and a white ppt would form and MgSO4 is soluble so no ppt would form.
Ba2+ + SO42- -> BaSO4
H2SO4 + 8H+ + 8e- -> H2S + 4H2O (i think H2s was the desired product... i dont even rememebr lol)
2I- -> I2 + 2e-
I wont list the advantages and disadvantages of fermentation, they'll have a range of options
when it asked about wanting to form one product to form over another or something it was KOH/NaOH and alcoholic
an answer for one of the questions about different intermediates forming was that it formed via the secondary carbocation which is more stable than a primary carbocation
The two environmental reasons were no SO2 produced which causes acid rain and the other is no CO2 produced which is a greenhouse gas. The economic reason was that scrap iron is cheap.
Cu2+ (aq) + Fe (s) -> Cu(s) + Fe2+ (aq) i think i put, cant remember
TiO2 + 2Cl2 + 2C -> TiCl4 + 2CO
TiCl4 + 2Mg -> 2MgCl2 + Ti
TiO cannot be extracted using carbon as titanium carbide is formed which is brittle.
ZnS + 1 1/2O2 -> ZnO + SO2
I think i got enthalpy of formation for the first one as low -300 or sumthin, i cant remember so feel free to correct me, It wasnt -1000 like others said as it was calculated from enthalpy of combustion data so u do reactants-products and not the usual products-reactants. The C-C bond i think was 300 and sumthin, i dont remember.
That's all i can remember for now, sorry for the vague questions and answers but hopefully it should help some ppl
(edited 7 years ago)
Just thought I'd mention, the equation for the ZnS
ZnS + 3/2O2 > SO2 + ZnO
Zinc oxide not Zn
ZnS + 3/2O2 > SO2 + ZnO
Zinc oxide not Zn
What did you guys get for the mean bond enthalpy?
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Overall it was a great paper , 85 minimum for an A because you have to consider that everyone taking this exam was re-sitting.
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Original post by Mo2351
Overall it was a great paper , 85 minimum for an A because you have to consider that everyone taking this exam was re-sitting.
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I disagree about the grade boundaries. It was a really good paper yeah, if you know the content. On the other hand this paper was unlike the past papers for CHEM2 and seriously stretched your knowledge and understanding of the spec; normally theyd just ask you the test for aldehydes/ketones etc and the mechanism questions are usually 5 marks, rarely seeing the requirements for a condition. I guess they did this because they knew A2 students were the only ones sitting it. But i know people that found it very hard. Also, everyone retaking are people that presumably did bad last year, so hopefully theres a bunch of *****ers to pull the grade boundaries down lol.
Original post by Mo2351
Overall it was a great paper , 85 minimum for an A because you have to consider that everyone taking this exam was re-sitting.
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EVERYONE
This is not true I emailed AQA and they are taking account that only we are sitting the paper, so grade boundaries should be as usual! Everyone needs to stop making up these rumours
(edited 7 years ago)
Original post by Engineerrookie
EVERYONE
This is not true I emailed AQA and they are taking account that only we are sitting the paper, so grade boundaries should be as usual! Everyone needs to stop making up these rumours
This is not true I emailed AQA and they are taking account that only we are sitting the paper, so grade boundaries should be as usual! Everyone needs to stop making up these rumours
Spoiler
Original post by Engineerrookie
EVERYONE
This is not true I emailed AQA and they are taking account that only we are sitting the paper, so grade boundaries should be as usual! Everyone needs to stop making up these rumours
This is not true I emailed AQA and they are taking account that only we are sitting the paper, so grade boundaries should be as usual! Everyone needs to stop making up these rumours
Grade boundaries go off of overall performance right?
Original post by Jackmilne95
Questions I can remember:
Magnesium observations were bright white flame and white solid.
simple magnesium and steam equation
MBD graph was displaced to the right with a lower peak.
Decreased pressure increases yield as right side has fewer moles so the equilibrium will shift to the right to oppose the increase in pressure blah blah.
Using 300degrees will keep the rate high whilst keeping the yield high. If temps above 300 were used the equilibrium will shift to the left (endothermic direction) to oppose the increase in temp since the forward reaction is exothermic.
Enthalpy of combustion is the enthalpy change for one mole of a compound to burn completely in oxygen with all reactants and products in standard states
A was butan-2-ol and B was butan-1-ol due to silver mirror etc
T was carboxylic acid and S was aldehyde i think
(Z)-pent-2-ene and (E)-Pent-2-ene I think they were. Geometrical isomers formed due to restricted rotation about the C=C bond.
For mechanism of 2 different reactions the reagent was KOH/NaOH and the conditions were ethanolic and heat under reflux for one and aqueous for the other, i think that what i put. The reagent acted as a base in one and electrophile in the other.
The free-radical substitution question was easy plus the CClF3 was split into two species with a free radical on each.
for the question about why it is dangerous to acidify the solution of nacl and naclo or whatever, i put that when increasing the conc of H+ ions the equilibrium will shift to the left and the conc/moles of Chlorine gas will increase and chlorine gas is toxic in high concs
For the Mg and Ba question where the two solutions mix i said BaSO4 is insoluble and a white ppt would form and MgSO4 is soluble so no ppt would form.
Ba2+ + SO42- -> BaSO4
H2SO4 + 8H+ + 8e- -> H2S + 4H2O (i think H2s was the desired product... i dont even rememebr lol)
2I- -> I2 + 2e-
I wont list the advantages and disadvantages of fermentation, they'll have a range of options
when it asked about wanting to form one product to form over another or something it was KOH/NaOH and alcoholic
an answer for one of the questions about different intermediates forming was that it formed via the secondary carbocation which is more stable than a primary carbocation
The two environmental reasons were no SO2 produced which causes acid rain and the other is no CO2 produced which is a greenhouse gas. The economic reason was that scrap iron is cheap.
Cu2+ (aq) + Fe (s) -> Cu(s) + Fe2+ (aq) i think i put, cant remember
TiO2 + 2Cl2 + 2C -> TiCl4 + 2CO
TiCl4 + 2Mg -> 2MgCl2 + Ti
TiO cannot be extracted using carbon as titanium carbide is formed which is brittle.
ZnS + 1 1/2O2 -> ZnO + SO2
I think i got enthalpy of formation for the first one as low -300 or sumthin, i cant remember so feel free to correct me, It wasnt -1000 like others said as it was calculated from enthalpy of combustion data so u do reactants-products and not the usual products-reactants. The C-C bond i think was 300 and sumthin, i dont remember.
That's all i can remember for now, sorry for the vague questions and answers but hopefully it should help some ppl
Magnesium observations were bright white flame and white solid.
simple magnesium and steam equation
MBD graph was displaced to the right with a lower peak.
Decreased pressure increases yield as right side has fewer moles so the equilibrium will shift to the right to oppose the increase in pressure blah blah.
Using 300degrees will keep the rate high whilst keeping the yield high. If temps above 300 were used the equilibrium will shift to the left (endothermic direction) to oppose the increase in temp since the forward reaction is exothermic.
Enthalpy of combustion is the enthalpy change for one mole of a compound to burn completely in oxygen with all reactants and products in standard states
A was butan-2-ol and B was butan-1-ol due to silver mirror etc
T was carboxylic acid and S was aldehyde i think
(Z)-pent-2-ene and (E)-Pent-2-ene I think they were. Geometrical isomers formed due to restricted rotation about the C=C bond.
For mechanism of 2 different reactions the reagent was KOH/NaOH and the conditions were ethanolic and heat under reflux for one and aqueous for the other, i think that what i put. The reagent acted as a base in one and electrophile in the other.
The free-radical substitution question was easy plus the CClF3 was split into two species with a free radical on each.
for the question about why it is dangerous to acidify the solution of nacl and naclo or whatever, i put that when increasing the conc of H+ ions the equilibrium will shift to the left and the conc/moles of Chlorine gas will increase and chlorine gas is toxic in high concs
For the Mg and Ba question where the two solutions mix i said BaSO4 is insoluble and a white ppt would form and MgSO4 is soluble so no ppt would form.
Ba2+ + SO42- -> BaSO4
H2SO4 + 8H+ + 8e- -> H2S + 4H2O (i think H2s was the desired product... i dont even rememebr lol)
2I- -> I2 + 2e-
I wont list the advantages and disadvantages of fermentation, they'll have a range of options
when it asked about wanting to form one product to form over another or something it was KOH/NaOH and alcoholic
an answer for one of the questions about different intermediates forming was that it formed via the secondary carbocation which is more stable than a primary carbocation
The two environmental reasons were no SO2 produced which causes acid rain and the other is no CO2 produced which is a greenhouse gas. The economic reason was that scrap iron is cheap.
Cu2+ (aq) + Fe (s) -> Cu(s) + Fe2+ (aq) i think i put, cant remember
TiO2 + 2Cl2 + 2C -> TiCl4 + 2CO
TiCl4 + 2Mg -> 2MgCl2 + Ti
TiO cannot be extracted using carbon as titanium carbide is formed which is brittle.
ZnS + 1 1/2O2 -> ZnO + SO2
I think i got enthalpy of formation for the first one as low -300 or sumthin, i cant remember so feel free to correct me, It wasnt -1000 like others said as it was calculated from enthalpy of combustion data so u do reactants-products and not the usual products-reactants. The C-C bond i think was 300 and sumthin, i dont remember.
That's all i can remember for now, sorry for the vague questions and answers but hopefully it should help some ppl
I'm afraid it butanal and Butanone that gave the silver mirror and etc - you didn't need to mention butan-1-ol and 2 as that's given in the Q - the question said what is P and Q not what is is A and B
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Original post by Jackmilne95
Grade boundaries go off of overall performance right?
I got the impression they make rough grade boundaries then look at the distribution of results, but they are fully aware that only we are sitting the exams so overall things might be higher but they will be taking this into account
And yes this was a harder than average exam, although it was do able but no doubt harder than others
Original post by ahsan_ijaz
I'm afraid it butanal and Butanone that gave the silver mirror and etc - you didn't need to mention butan-1-ol and 2 as that's given in the Q - the question said what is P and Q not what is is A and B
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Are you 100% sure?
Original post by Engineerrookie
Spoiler
What do you mean by this? Its kind of ambiguous what you're saying.
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Original post by Engineerrookie
I got the impression they make rough grade boundaries then look at the distribution of results, but they are fully aware that only we are sitting the exams so overall things might be higher but they will be taking this into account
And yes this was a harder than average exam, although it was do able but no doubt harder than others
And yes this was a harder than average exam, although it was do able but no doubt harder than others
Oh ok. I am pretty confident that the grade boundaries will be lower than last year
Original post by Jackmilne95
Are you 100% sure?
I'm pretty sure it said what A and B are, I double checked
Original post by Engineerrookie
I'm pretty sure it said what A and B are, I double checked
So it was not necessary to write butan-1-ol and butan-2-ol right?
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Original post by ELCRE
there are rumours that because A2 students are the only ones sitting these AS exams so the grade boundaries will be high. I am saying that these rumours are not true, I emailed AQA and they are taking into account that the distribution of results may be higher because we are all resisting students this year, but this shouldn't affect the grade boundaries this year as they are taking into account this. Grade boundaries should be as usual around 70-85 not higher than average.
Original post by Engineerrookie
I'm pretty sure it said what A and B are, I double checked
Yeah, and those were the primary and secondary alcohols right?
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