AQA A-Level Chemistry Paper 2 (7405/2) - 19th June 2023 [Exam Chat]

i assume its simply because no other info is provided and the question explicitly says it is an ester so he added the CH3-O- to form the ester as this must be the structure based off of the rest of the information provided

ohhh okay that makes sense but then why isnt it CH2CH3 instead of just CH3 like that’d still be an ester ? cause like quartet so 3 hydrogens adjacent so should it not be as the right side is set up ??

likely because of the wavelength being within the range that suggests that the quartet is attached to C=O

guys im really struggling with organic and scared for monday. any tips on how to actually understand the content and get as many marks in the exam. i really hope there's lots of physical stuff on there if not im screwed

Do you think theres any point doing 2021 and 2020 ppq since the exams were cancelled for that year?

I mean, practice is practice - they're still valid questions so I would do them if I was in your place. However if you feel your revision would be more efficient doing something else and it would make you feel better, then do that Hope this helped.

does anyone know if we need to know the aquation for how tollens reagent reacts with an aldehyde?
CH3CHO + 2Cu2+ 4OH- -----> CH3COOH + Cu2O + 2H2O

We do - is that the equation? I thought it was this:
RCHO + 2[Ag(NH₃)₂]⁺ + 3OH⁻ → RCOO⁻ +2Ag+ 4NH₃ + 2H₂O

(from AQA 2017) 1. A second TLC experiment was carried out using 1,2-dinitrobenzene and
1,4-dinitrobenzene. An identical plate to that in Question 8.3 was used under
the same conditions with the same solvent. In this experiment, the Rf value of
1,4-dinitrobenzene was found to be greater than that of 1,2-dinitrobenzene.
Deduce the relative polarities of the 1,2-dinitrobenzene and 1,4-dinitrobenzene
and explain why 1,4-dinitrobenzene has the greater Rf value


please can someone explain how to answer these type of questions. I don't understand what it means by polar/non polar attractions with stationary/mobile phase and the effect it has

2. State in general terms what determines the distance travelled by a spot in TLC.
-Balance between solubility in moving phase and retention by stationary phase - what does that even mean?

basically in TLC substance you want to use is place on a plate (stationary phase) and carried up it using a solvent (mobile phase)
both the plate and solvent can be polar or nonpolar
polar substances are attracted to polar solvents/surfaces and vice versa
therefore, more polar substances will travel further in polar solvents due to them having a greater affinity for eachother

in terms of this question, it can be deduced that 1,2dinitrobenzene is more polar due to its arrangement of polar groups and therefore it will have a lower affinity to the nonpolar solvent and a higher affinity for the polar TLC plate that is being used.
Therefore, it has a lower retention time due to it not being as attracted to the mobile phase.
The inverse can be said about 1,4ndinitrobenzene

thanks. if affinity to the polar/non polar solvent affects how far it moves up the plate then what effect does affinity to the polar/non polar stationary phase have?

what does lower retention time mean?