First day of specialty test and fourth most chosen specialty among final year high school students: 122,183 candidates must take their Physics Chemistry specialty test this Wednesday (Day 1) or Thursday (Day 2), depending on their invitation. Here is the first answer for the test which took place this Wednesday between 2 p.m. and 5:30 p.m.
This answer key is written by Elisabeth, high school teacher, Physics Chemistry teacher. Here is his comment on the subject: “ Very classic exercise 1 on the synthesis of a chemical species which covers a substantial body of associated knowledge and know-how.
Classic exercise 2 without any difficulty, scanning the astronomical telescope and the Doppler effect.
Mechanical exercise 3 without major difficulty. We study the fall of an object without friction then with friction, which allows us to deduce comments on the relevance of neglecting the force of friction.
Answer key to the subject of Physics Chemistry for bac 2024 – Day 1
Exercise 1 – Towards thymol blue
1. Raw formula:
It is a phenol group
2. The thymolate ion of its name 2-isopropyl-5-methylphenol whose Lewis formula is:
3. The TLC of the essential oil obtained is made up of 3 tasks so it is a mixture. One of the tasks has a frontal relationship identical to that of thymol. So the essential oil obtained consists of a mixture including thymol.
4.
5. The solubility of thymol is low in water so it is found in the organic phase which is above
6. To obtain 1g of thymol you therefore need 1/0.31 = 3.2g of crystals We know that there is a mass percentage of thymol in the oil of 53%, i.e. an oil mass of 3. 2/0.53 = 6.1 g of oil
However, 100 g of thyme allows you to obtain a maximum of 2 g of oil, i.e. 6.1×100/2 = approximately 304 g.
7. P2 has the same chemical formula as thymol so it is an isomer. On the other hand P4 does not have the same crude formula so it is not an isomer
8. A catalyst is a substance that accelerates a chemical reaction without being consumed by it. This means that it participates in the reaction by facilitating its progress, but it remains unchanged at the end of the reaction. The use of a catalyst makes it possible to reduce the synthesis temperature by lowering the activation energy of the reaction. Activation energy is the amount of energy required for reactants to reach the transition state and transform into products.
9. Here are the main interests:
Le Chatelier’s principle: By increasing the concentration of one of the reactants (here, propene), the reaction is shifted towards the formation of products. This helps maximize the conversion of m-cresol into desired products.
A higher concentration of propene can increase the frequency of collisions between propene and m-cresol molecules, which can accelerate the rate of the reaction.
Propene is often a less expensive reagent compared to m-cresol.
10. The boiling temperatures of m-cresol and thymol are very different: they will therefore be separated by fractional distillation. As m-cresol has a lower boiling temperature it will be recovered first
The complete answer key for the 3 exercises below:
Physics, chemistry is also often associated with Mathematics or SVT.
Also consult the other topics and corrections:
Good luck to everyone for the second day of the test which will take place this Thursday, June 20.
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