AQA AS Chemistry May 23rd 2019 UNOFFICIAL MARKSCHEME

That was not a question

mark scheme for the questions I can remember, please feel free to correct/add


•reagent for ketone and carboxylic acid- sodium carbonate
see nothing for ketone and fizzing for the acid
reagent for ketone and aldehyde-Fehling’s solution/Tollen’s reagent
see nothing for ketone
solution goes red for aldehyde/silver mirror formed

•nucleophilic substitution, Br was replaced by CN
this formed propanenitrile
atom economy was 38.1% (or thereabouts)

•hess cycle gave a value of -160
different value due to heat loss to the surroundings/incomplete combustion

•C₈H₁₈ + 12.5O₂ ➝ 8CO₂ + 9H₂O

•1)a catalyst doesn’t affect the position of equilibrium but does affect the rate at which equilibrium is attained, faster rate of reaction by offering an alternative reaction pathway with a lower activation energy
2)forward reaction was exothermic so lower temperatures will increase the equilibrium yield as the system shifts to oppose the change, compromise is made however so a faster rate of reaction can be attained as higher temperatures increase the number of particles with activation energy leading to more frequent successful collisions, higher temperatures increase costs as more energy required
3)less molecules of gas on the right side so high pressures increase equilibrium yield as well as rate of reaction due to there being more particles within a given volume, however high pressures are expensive to maintain

•mass of CaO required- 5.4x10^9 kg

•electrophilic addition
isomer E is formed via a secondary carbocation, which is more stable than the primary carbocation that isomer Z is formed from, hence meaning more of it is produced

•change in temperate (q=mcΔT) + initial temperature gave a final temperature of 62.7 degrees celsius

•mass required- 130mg
distillation apparatus drawn as the alcohol was oxidised to a aldehyde and not fully to a carboxylic acid as it would under reflux

CCl₂F₂ ➝ •CClF₂ + Cl•
Cl• + O₃ ➝ ClO• + O₂
ClO• + O₃ ➝ 2O₂ + Cl•

•forming a standard solution:
1)put the mass of the solid in a weighing boat and place on a mass balance, recording the mass
2)pour the solid into a conical flask and reweigh the boat
3)mass of the solid=initial mass-final mass
4)add distilled water to the conical flask until all of the solid has dissolved, and use a stirring rod to ensure this
5)pour the contents into a volumetric flask, using distilled water on the conical flask and stirring rod to ensure that all of the contents have entered
6)fill the flask up to 250cm^3 with distilled water, adding it drop by drop using a pipette towards the end-stop when the bottom of the meniscus lies on the line
7)place a stopper on the flask and invert multiple times

•hydrogen bonding (lone pairs on the oxygen)
bond angle of 104.5 due to lone pairs on the oxygen repelling more than bonding pairs, thus giving it a bent shape and reducing the angle from 109.5

•volume of gas was 15000cm^3
volume of liquid was 65 (ish) cm^3
expansion factor of around 230

Hey I'm doing my AS Chemidtry mock exam and teacher is giving us paper sent by AQA will it be this paper?

Most likely, although sometimes there are alternative papers that AQA can use as well