AQA A level chemistry 2020 autumn paper 3 unofficial MS

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Poll: estimated marks?
>=80 (1)
3.85%
75-79 (5)
19.23%
70-74 (2)
7.69%
65-69 (1)
3.85%
60-64 (3)
11.54%
55-59 (5)
19.23%
50-54 (3)
11.54%
40-49 (2)
7.69%
30-39 (2)
7.69%
20-29 (1)
3.85%
<=19 (1)
3.85%
ish101
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1.1 explain how oxides of nitrogen are produced in engines [2]
there's a high temperature+pressure in the engine which causes the N2 and O2 to react, the NO produced can then react further with the O2 to produce more such oxides
1.2 why is it beneficial to remove nitrogen oxide emissions? [1]
it causes pollution, can cause acid rain
1.3 adblue, oxidation states of nitrogen in various compounds, and then equation balance for reaction [2]
+4 (NO2), +3 (NH3), 0 (N2)
6NO2 + 8NH3 --> 12H2O + 7N2
1.4 state what a heterogeneous catalyst is [2]
a substance that lowers the activation energy of a reaction, and is not in the same phase as the reactants
1.5 why is particulate carbon produced [1]
incomplete combustion of hydrocarbons

2.1 magnesium and sodium oxides react with water. state why they form alkaline solutions. explain why the sodium oxide solution has a higher ph [2]
i wrote equations for each, said they release OH- ions. NaOH fully dissociates, whereas Mg(OH)2 barely does so (it's sparingly soluble)
2.2 give the equation for the reaction between phosphorus(V) oxide and water [1]
P4O10 + 6H2O --> 4H3PO4
2.3 give equations to show how vanadium (V) oxide catalyses and is remade in the contact process [2]
V2O5 + SO2 --> SO3 + V2O4
V2O4 + 1/2O2 --> V2O5 (or 2V2O4 + O2 --> 2V2O5)

3.1 why do transition metal ions form coloured complexes [3]
when ligands bonds with the metal ion, it splits the d sub-shell orbitals. there is an incomplete d sub-level in the metal ion, so e-s can get excited and move up to a higher energy orbital by absorption of a photon of a specific wavelength. all other wavelengths are not absorbed, and are what give the complex its colour
3.2 plancks equation for the energy of a photon (absorbed), find the energy of a 490nm photon [3]
4.0x10^-19J i think
3.3 explain how colourimetry is can be used to find the conc of the iron [3]
using Fe3+ solutions of known concs, plot a graph of absorbance against [Fe3+], then read off the absorbance value for your solution from this graph
3.4 mass of iron in the tablet [2]
65mg or something?

4.1 what is the process stopped by cisplatin? [1]
any ONE from (answer disagreement between users) either:
- DNA replication
- cell mitosis (although i put cell mutation lol, which is wrong i'm pretty sure)
4.2 ligand sub reaction, chlorine for a water ligand [2]
[Pt(NH3)2Cl2] + H2O --> [Pt(NH3)2 Cl H2O]+ + Cl-
4.3 draw on how the cisplatin complex attaches to the 2 guanines in dna, displacing the water and Cl- ligands [2]
the free N's on guanines will dative covalently bond to the Pt
4.4 explain how you could find the order of the reaction using graphical methods [3]
anyone remember the exact Q? can't remember my answer
along the lines of, plot a conc time graph. then deduce the instantaneous rate at regular intervals, from the tangent to the graph at those concentrations. then if rate conc graph has constant negative gradient it is order 1. if gradient 0 then order 0. if (increasing) changing gradient then order 2.
4.5 activation energy and arrhenius equation graph plot [5]
105kJmol^-1 (range will be allowed)

5.1 find Ccal [3]
7.79 or something
5.2 find the heat change [2]
5040 or something
5.3 why is this not an enthalpy change [1]
can't remember units of previous Q
- if previous Q had units of kJK^-1: this is a measure of the energy taken in when the temperature raises by 1deg, rather than per mole of fuel burnt
- if previous Q had units of kJmol^-1: substances not under standard conditions (this is what i put, but is the unlikely option i think, as bomb cal could withstand pressure changes)
5.4 percentage uncertainty [2]
1.67% or similar (should have multiplied 0.1 by 2, then divide by deltaT and x100)
use greater no. of moles of fuel (so you get a greater deltaT)

6.1 give the conditions etc. required in a standard H2 electrode [3]
- 1M of H+ ions (aqueous)
-298K, 100kPa pressure
- H2 gas with a Pt electrode
6.2 6 marker, find the standard electrode potential of the Ti/(TiO)2+ electrode using stuff given [6]
... discuss below haha
6.3 give equation for the reaction happening at the Ti electrode [1]
Ti + H2O --> (TiO)2+ + 4e- + 2H+
6.4 why does Cu not react with nitric acid, give equation [3]
Cu must be oxidised when it reacts, E(H2/H+) < E(Cu/Cu2+) so it can't be oxidised by any other acid generally. E(NO3-/NO) > E(Cu/Cu2+) so it can be oxidised by NO3- ions
standard equation, can look up (don't wanna type it)
Last edited by ish101; 1 month ago
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Harrybeld
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DNA replication for 4.1 I believe
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asdasdihpi
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Am I the only one who got 8.3 for that Ccal one?
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Harrybeld
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(Original post by asdasdihpi)
Am I the only one who got 8.3 for that Ccal one?
I got 7.9 as well I think
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Harrybeld
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Also I think for 2.3 it was to write equations for the steps in the contact process which are: V205 + SO2 -> V204 + SO3 and 2 V204 + O2 -> 2V205
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ish101
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(Original post by Harrybeld)
Also I think for 2.3 it was to write equations for the steps in the contact process which are: V205 + SO2 -> V204 + SO3 and 2 V204 + O2 -> 2V205
ah that's the one, i'll add it on
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asdasdihpi
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(Original post by Harrybeld)
I got 7.9 as well I think
Ahh okay must’ve done something wrong then
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dontworrymyg
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#8
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Yo I appreciate you making this bro creds to you!!! Or if you're a sis idk but ty ty
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dontworrymyg
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#9
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Could you make an estimation poll like last time please?
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ish101
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(Original post by dontworrymyg)
Yo I appreciate you making this bro creds to you!!! Or if you're a sis idk but ty ty
np haha, it didn’t even rly take too long (bro )
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ish101
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(Original post by ish101)
np haha, it didn’t even rly take too long (bro )
(Original post by dontworrymyg)
Could you make an estimation poll like last time please?
yep just did
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Anonymous17!
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#12
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Got 16 marks so far. **** me I messed up the heterogeneous catalyst I said same state even though I know difference between heterogeneous and homogeneous. Damn. Guess my other marks will come from my multiple choice. What did everyone’s graph look like and what scale did you use, I used 2.
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RoseWS5
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Question 1.2 was the "why is it desirable to reduce nitrous oxide emissions"
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ish101
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(Original post by RoseWS5)
Question 1.2 was the "why is it desirable to reduce nitrous oxide emissions"
oh true completely forgot, ty
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dontworrymyg
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For 4.4 I don't think the gradient=order. Ithink it's the shape of the graph, horizontal=0 linear positive correlation=1st. Cumulatively increasing line _) =2nd
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RoseWS5
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I'm assuming the poll includes MCQ marks? Got ~45 for section A being harsh and I didn't find myself going "oh I've barely gotten half"

Counted them up. Does include MCQs. Can't really give a good estimate. How many MCQs were there?
Last edited by RoseWS5; 1 month ago
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dontworrymyg
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(Original post by RoseWS5)
I'm assuming the poll includes MCQ marks? Got ~45 for section A being harsh and I didn't find myself going "oh I've barely gotten half"

Counted them up. Does include MCQs. Can't really give a good estimate. How many MCQs were there?
What was section A out of?
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ish101
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(Original post by dontworrymyg)
For 4.4 I don't think the gradient=order. Ithink it's the shape of the graph, horizontal=0 linear positive correlation=1st. Cumulatively increasing line _) =2nd
yeah exactly, it's essentially the gradient that's different about the 3, if it's horizontal the gradient will be 0, if positive correlation then you get a positive constant gradient, if a cumulative increase then the gradient will be increasing continuously. the gradient has a say on the shape of the graph. although, i think i still got it wrong in the exam as i forgot to mention plotting a rate conc graph (changed it in the answers above), which is what would allow the order deduction, i don't think you can rly deduce order from a conc time graph
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ish101
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(Original post by RoseWS5)
I'm assuming the poll includes MCQ marks? Got ~45 for section A being harsh and I didn't find myself going "oh I've barely gotten half"

Counted them up. Does include MCQs. Can't really give a good estimate. How many MCQs were there?
yeah including, there are 30, ig if they went well and you answered everything, just take away 3 (take into account potential silly mistakes), and if they went iffy and you didn't answer a few, then take away 5-10 accordingly, etc. just an estimate rly
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random678
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(Original post by Harrybeld)
I got 7.9 as well I think
same i got this
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