AQA A-Level Chemistry Paper 2 markscheme

he total mark for this paper was 105 with 9 questions. Please add to it as much you can. The above is the archive, however this document can still be edited for debate/additional information. Please keep in mind this is a student made mark scheme, and these answers may not all be what is on the official mark scheme. Topic for Paper 3: DNA, Chromatography, aspirin production Question Answer Additional Information/Debate Mark s 1 why use a conical flask instead of a beaker? I put it has a smaller opening than a beaker so less gas lost?? You want to lose gas? - I am pretty sure this is the right answer, well it decreases the rate of gas no loss so easier to measure the rate. It doesn't reduce the rate of gas loss as this only depends on the concentration of reactants No splashing This was jokes Reactants don't stick to the side what?????? they would stick a little regardless what was the cotton wool in that diagram for lolz it threw me off I put that the liquid would be shallower with larger surface areaso gas produced could escape quicker I put larger surface area for to heat mixture more evenly? I said this too You dont want to have a large opening bc the acid may be lost due to the bubbles forming. Anything about swirling? I wrote swirling 1 rate at 2 minutes. 0.5 g min-1? This is correct. A range of values typically accepted. I got 0.4 so yeah they’ll accept a range AS LONG as they can see how you worked it out. G min-1 ? Yeah but if u changed to seconds it wouldn’t really matter as long as u put g per second Mol Dm-3s-1 + I got 0.02, you had to convert to mols - you didn’t have to, any appropriate units would be fine I got like 0.0175 gs-1 - Same here - yeah just rounded Gmin-1 no? Is it not gmin-1 the graph was in minutes I converted the minutes to seconds and put my units with seconds as well, any idea if thats okay? Yes 3 Suggest why chloroethanoic acid is stronger than ethanoic acid (this question is already discussed a little further down.) fill in rate table 1.00 0.16 1.35 I beg someone write what the values were if they remember K=250 Yes i agree - needs to be 1.4 as all values were to two sig figs Weren’t we they to 3 dp though? The rate of the first one was 1.00 so I’m guessing 3sf of 2dp 3 empirical formula C6H10O3S2 Percentages dudbt add up to 100 fuck me Didn’t even see the sulphur, fml same same i thought i meant i was in the fuel area. YAY i got this!! 3 the labelling distillation for the tube it was fractionating column or glass beads the bottom of the condenser was water in and top was water out reject anti bumping granules might accept silica BEADS 3 Draw a line for the reaction with chloroethanonic acid Suggest why chloroethanoic acid is a stronger acid than ethanoic acid. Was the line of chloroethanoic acid to the left of the first line, but levelled off at the same point? Yes but it levelled out before, same height though. Ah ok. Dissociates more Chlorine is more electronegative than hydrogen so will withdraw electron density form the carboxyl group meaning that the O H bond breaks more easily dissociating into H+ making the solution more acidic Cl is electron withdrawing, it polarises the bond, weakens the O-H bond which releases more H+ than ethanoic acid Neg inductive effect? Chloroethanoic acid forms a more stable conjugate base? 3 NMR Question? Use the integration values and the ratios to identify the structure at two peaks. Draw this structure. Was there a typo though? Regarding what? No dont think so, it was just because 2 of the peaks were the same environment almost so people got thrown off 5 2 1 2 I have structure Ignore circles. Final structure was something like CH3COCH2CH2COOCH2CH3 Nah chemical shift values can sometimes be outside ranges, as my teacher said They shouldn’t be though… that was evil even though i worked it out I’m crying why didn’t i see a question that asked for the full structure.. was it 1 mark?? - Yes it was 1 mark for the final structure - Thank god - Thought it was 2? - Piss off jokes xx - Ah ok. Hard to read tone over google doc lmao. yh true soz np - you had to work out the structure for 2 marks like the separate ones where they gave you the values Rate-determining step Step 2 Steps up to and including Step 2 had a total of 2 moles of B and 1 mole of H+ on reactant side, matching the powers to which [B] and [H+] are raised in the rate equation how did u explain why it was 2 oh cool thank u i think i put something like that lol Dk how to explain it but basically the rate equation contained two B’s and one H so it had to be Step 2 which contained B and BH, but but BH is made up of B and H which satisfies the rate equation 2 Name of mechanism Electrophilic substitution I put nitrification and (electrophilic substitution) in brackets nitration is not the name of the mechanism but they may accept if you included both How many marks was drawing the mechanism before this? the nucleophilic addition elimination was 4 marks nitration was 3 marks nucleophilic addition was 4 marks 1 2nd name of mechanism Nucleophilic addition 1 name isomer W 3-bromopropanenitrile yea :) - could you say 3-bromopropane-X-nitrile (X being the carbon the nitrile was on?) 1 maybe but idk bro ^^With IUPAC you count the first carbon to be the one from the nitrile 1 Identify the reagent that is warmed with isomer W in reaction 2 KCN - Ethanolic and aqueous number? But in a water / ethanol mixture (ethanolic) no wasn’t it ethanolic kcn - I put ethanolic as well…, yea cool I SAID HOT ETHANOLIC DOES THAT COUNT? I think so. 2 Reaction 3 H2 and pt think u can have h2 and nickel? - Yep - Nickel