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Doing this paper, I realised I did not revise enough and tend to spend time recalling for information that I should have recalled right away. I tend to not have enough time for the paper and therfore not enough time to chdck.

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From reviewing the video, Ive highlighted my weakpoints, of which are
: Careless mistakes
: Counting isomers
: The disproportionation reactions of Chlorine with sodium hydroxide

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Revise on which is cis and which is trans, periodicity and catlyst along with conditions for reactions

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I learnt about the graphs of period 3, how to identify stereoisomers and structural isomers, propagation reaction of halides. I had to recheck and found some careless mistakes which I should pay more attention to in the future.

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Through the Chemistry AS Prelim P1, I realised that I have many careless mistakes that cost me a lot of marks. I need to be more careful when answering the questions and I need to practice more so that I will be able to answer at a faster pace. Overall, I feel that I have a rough idea of the topics being taught but my knowledge is still insufficient to say that I have a good grasp of the subject, therefore I will revise more on the topics to be better at tackling the different types of questions, even those that are not within the syllabus. I realised that I had difficulties applying what I have learnt as I relied heavily on memorisation instead of understanding and mastering the topic.

Through this test, I have learnt/revised the following:

1. Enthalpy of atomisation and enthalpy of ionisation are always endothermic.

2. Phosphorus can form P4O10 or P4O6

3. Carbonates become more thermally stable going down group 2 (ex: SrCO3, BaCO3).

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From the P1 Chemistry Prelims, I definitely need to learn more of the nuanced / detailed section of the syllabus T^T. Polymer interaction, isomers (and counting them), group 2 carbonates and their reactivity, and their electronegativity trends are some of my weak points shown from P1.

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The questions that involved Br were merciful. I need to revise more on questions with diagrams.

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From this prelims paper, I learned that I should understand and memorize concepts such as trends better, read questions more thoroughly, manage time better so I can recheck my answers and avoid careless mistakes, practice and do more questions, revise topics in depth.

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I learnt that mastering the concept is not enough, you must also be careful when doing the questions. In this paper I learnt about the shape of BF4- has a square planar structure. I also learnt about the trends in both Group 2 and Group 7 which are quite puzzling at times. Furthermore, I need to be more careful when counting the number of stereoisomers and positional isomers there are.

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From the P1 AS Prelims, one of the most important things I learnt is about how stereoisomerism can be formed — for example, in No. 26, I learnt how many different hydrocarbons can be produced when 3-bromo-3-methylpentane reacts with excess ethanolic sodium hydroxide.

Overall, I also learnt that it is important to take note of the time especially in Paper 1, so I would be able to have more time to go through my answers and not make any careless mistakes, just like in No. 35 where I didn't analyze the statements regarding hydrogen halides properly.

After the Prelims, I more or less know what are my strengths and weaknesses — and know what I should focus on more in preparation for the future ALevel Exams, and how to improve from my past mistakes.

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the questions in this paper was okay except i made some mistakes with the calculation and i need to revise more on structures and the substitution of mechanisms and learn to analyze the drawings more. i also need to remember the colour of certain compounds and memorize them carefully. overall i need to understand and memorize certain topics more thoroughly especially the drawings of mechanisms and memorizing the colours.

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I  revised about the AgBr, AgCl, AgI precipitate, some group 2 carbonates and nitrates such as Ba,Sr  need higher energy to decompose, bond angles and shapes, and electrongativity trends across period and down the group.

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In the discussion revised about the
-Chiral Centers
-The term Isoelectronic
-Periodicity
-Sn1 and Sn2
-Free Radical Subsitutions
-Enthalphy changes reactions and computations

In this paper i did a lot of mistakes due to not reading more and need to put in more time in revising the topics

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I have learnt to pay more attention to the wording of the questions and consider all possible alternatives. Furthermore, I have realised the importance of reading through the options I deem incorrect and be able to prove why it is so. The most important of all, in my opinion, is to commit all concepts to memory in order to ensure that I do not overlook any steps in my working when answering the questions.

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Overall I felt that the paper was okay, but for some questions the instructions need to be read more carefully as some important information may be mentioned that was skipped.

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Found out i was weak in periodicity and trends of thermal stability and reactivity

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- isoelectronic : same number of electrons
- square planar structure : 4bp, 2lp
- radius of an atom gets smaller across the periodic table therefore nuclear attraction increases
- Kc and Kp is only affected by temperature
- boltzmann curve : higher temperate = lower peak, shift to the right
- AgCl : white, AgBr : cream, AgI : yellow
- chiral center : carbon having 4 different groups
- SN2 does not form carbocation, only intermediate

I need to practice more on the calculations for number of moles and counting the number of stereoisomerism that can be formed from a compound.

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In this paper, I made a careless mistake regarding isomerism.
I learnt about  th reaction of halogenoalkene with excess ethanolic sodium hydroxide.

I need to practice and review for the calculations.

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I need to read carefully and revise on the reactions of G2, 17 and period 3. I learnt about:
- isoelectronic, elements with the same number of electrons
- iodine is brown in liquid form, purple in gaseous state, black in solid form
- having a C=C bond does not always mean that it has a cis/trans isomer but it is still counted as 1 stereoisomer

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information to revise:

isoelectronic - no. of electrons the same

smaller size of atoms; stronger attraction to nucleus

atomisation - bond breaking; always +; IE - supplying energy; always + // formation can be + or -

poisonous gases - sulfur (SO2), ethane, nitrogen

acidic bond - carboxyl

SN2 - NO CARBOCATION! forms intermediate

triiodomethane - alcohol (OH group, H group, CH3, any R group) // aldehyde or ketone (CH3 and R group)

smiling ghost alcohol

only aldehyde can give positive reaction w tollen and fehling

"which of following quantities is equal to avogrado constant" - use 1 mole not 6.02x10^23...

polar is definitely permanent dipole-dipole

go down group, thermal decomposition more difficult (higher energy and temp. needed)

non-metals reactivity - ability to gain electron; H2 and I2 form equilibrium

answering exams:

when drawing, start with the easier molecules

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i made some silly mistakes in this prelims as for simple questions like number 1.
Things i revised on the video:
- Sterioisomers
- Halogenoalkanes
- How to count for chiral centres
- What isoelectric means
- Different bond angles and their structures (square planar especially)
- some enthalpy change will only be positive, negative or both
- going down the group, need more heat energy
- boltzmann curve

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reflection

1. ionisation energy is always endothermic (delta H = positive value)

2. isoelectronic is elements having the same no. of electrons

3. across periodic table, radius is getting smaller (nuclear attraction is more)

4. metalling bonding (bond between ions and delocalised electrons)

5. square planar structure = 4 bp, 2 lp

6. octahedral = 6 bp

7. ideal gas = high temperature and low pressure

8. enthalpy change of atomisation is always positive, neutralisation is negative, formation can be both, ionisation energy is positive, solution can be both, combustion is negative, hydration is negative

9. Kc and Kp is only affected by temperature

10. Kc = ignore (s)/solid

11. Boltzmann curve = higher temperature, peak lower and go to the right

12. SiO2 insoluble in water

13. cream precipitate (silver nitrate) —> bromide ions, white precipitate (silver nitrate) —>  chloride ions, yellow precipitate (silver nitrate) —> iodide ions

14. unsaturated (C = C)

15. chiral centre (carbon bonded with 4 different groups)

16. Sn2 (formation of intermediate)

17. tri-iodomethane (methyl ketones, ethanal, alcohol with CH3 group)

18. LCP principle, equilibrium shifts to the direction that reduces the change

19. carbonates decompose into oxides and carbon dioxide

20. Cl2 is more reactive than I2 (form equilibrium)

-- avoid careless mistakes

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P1 Reflection
- primary -> Sn2
- Electronegativity : attracting electrons in covalent compounds
- Carboxylic acid from nitrile
*RCN + HCl (aq) + H2O --> RCOOH + NH4Cl

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- Isoelectronic is the same number of electrons.
- 1 lone pair and 4 bonding pairs is square planar.
- 6 bonding pairs is octahedral
- Need to be more careful on oxidation number calculation
- Group 2 metals when reacting with water will form a hydroxide and hydrogen gas such that a gas is produced.
- SrCO3 does not decompose from heat.
- BaCO3 is difficult to decompose.
- Metal oxides react with aqueous hydrochloric acid to form salt and water such that there is effervescence.

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- careless mistake (both theory and calculation)
- lack of understanding  for equilibrium chapters (calculation)
- Lack of understanding for enthalpy chapter
- isoelectronic
-isomerism need practice
-polymerization need more practice

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I revised about:
- The colors of halogens in different forms (aqueous, gaseous)
- The features of Infra-Red Spectroscopy.
- The trends of Group 2 metals and their compounds.
- Isomers

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-Isoelectronic means that t has the same number of electrons
- phosphorus can form it's 2 oxides, P4O6 and P5O10
- 6 bonding pairs make up an octahedral
- Across a period, the ionic radius becomes smaller
- Going down the group, more heat is needed for thermal decomposition

In this prelim, i made alot of careless mistakes and just didn't know some questions in general. I need to memorize more reactions and conditions.

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Bromine is more reactive than iodine so displacement reaction will occur and the solution will become brown because I2 is brown in solution form. Dilute aqueous ammonia is not enough to dissolve AgBr so there will be a cream precipitate. Unsaturated means that the displayed formula must have double bond. Alcohol is neutral while carboxylic is acidic. Chiral centre means the carbon must have four different groups. Delta positive and delta negative will interact because they are polar so there will be permanent dipole interaction. All molecules will have van Der Waals forces so there will be temporary dipole-induced dipole interaction. As we go down the group, more heat will be needed for thermal decomposition so SrCO3 will not decompose.

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In this AS prelim, i made a lot of careless mistakes because I either didn't fully read the question or I read the questions and answers to fast resulting in mistakes.
-Isoelectronic means that elements have the same no of electrons
-Phosphorus can form 2 oxides which are P4O6 and P5O10
-Iodine is a brown liquid-gas in room temperature
-Effervesence is connected to the gas produced
-Reactions of halogenoalkanes

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Revised on :
- free radical substitution
- reaction of carbonates and acids
- isoelectronic -> same electron number
- chiral centres
- 1°, 2°, 3° halogenoalkanes
- SN1 and SN2
- bond angles and shapes
- enthalpy change
- boltzman distribution curve
- AgBr, AgCl, AgI precipitate colors
- electronegativity trends
- test for carbonyl compounds

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isoelectronic: having same no. of electrons

square planar structure: 1lp 4bp

enthalpy of combustion of H2 is the enthalpy of formation for H2O

sulfur and phosphorus can form two acidic oxides (P4O10 and P4O6)

I2 is brown in solution form

going down the group, harder to decompose

metal oxide react with HCl to form salt and water (there is no effervescent)