4s vs 3d - Which has the higher energy? Some of us may have learn this phrase "First In, First Out" or "FIFO" regarding 4s vs 3d. But why is the 4s orbital filled first? Ans: The simple answer is because 4s orbital is lower in energy than 3d orbital when they are empty. Qn: But isn't principle quantum n=3 supposed to have lower energy than n=4? Ans: Generally yes, but within the quantum shell, each subshell has slightly different energy levels due to their differing distance from the nucleus (when the subshell is further away from the nucleus, it has higher energy, as it experiences weaker attractive force) . It so happens that because of their shapes, there is ...
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Theories of acids and bases *New! Arrhenius theory – acid produce H+ in water, base produces OH- in water. Bronsted Lowry theory – acid produces H+, base accepts H+. Conjugate pair concept. Lewis theory – acid as electron pair acceptor, base as electron pair donor. Gases: Vm = 22.7 dm3 at stp (1 bar, 273 K), 24 dm3 rtp (1 atm, 293 K) Group 2 & 17 (no longer Roman Numerals) now under Periodicity. Group 17: Not required to describe the reactions of halide ions with sulfuric acid. Not required to describe the reaction of chlorine with cold and hot aqueous sodium hydroxide. Group 2: learn thermal stability of carbonates instead of nitrates. Equilibria: Show understanding that the position of ...
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'A' Level Chemistry Syllabus Overview of changes in weightage: Table taken from SEAB website All students required to take practical paper 4, including private candidates. This means that candidates retaking their A level chemistry paper this year will have to sit for a 20{8445fa0408f68c331c03e03f10d6a7bff33fb7168cc52e9b2191ddf5ec3671a6} weightage practical paper. Also, their previous SPA scores will not be counted. So you are a private student retaking A level H2 chemistry this year, do try to enroll yourself in a private school which provides practical lessons. 'A' Level Chemistry Syllabus weightage Paper 1 will be 30 MCQ (with 5-8 Multiple Completion Type) instead of 40 MCQ (10 MCT). Lower weightage. Paper 2 data-based question will be 20-25 marks out of 75 instead of 15-20 marks out of ...
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Permanganate titration Qn: Why can't we use hydrochloric acid or nitric acid for manganate (VII) redox titrations? Ans: For HCl, the chloride ion will be oxidised to chlorine gas by manganate (VII) ion. HNO3 is also an oxidising agent and hence would compete with permanganate. Lastly, permanganate cannot oxidize sulfate ion and sulfuric acid is not an oxidizing agent. Therefore, sulfuric acid is the mineral acid of choice for manganate (VII) titrations. More common questions here. Home ...
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J2 students, need some last minute help in Organic Chemistry before your Mid-Year Exams? Sign up for 4 lessons of intensive revision using 2016 Prelim structured questions from different JCs! Part 1 of our revision program covers the whole spectrum of organic concepts so do come prepared 🙂 Answers will be analysed together and misconceptions will be addressed on the spot. Dates: 7, 9, 14, 16 June Time: 2 - 5 pm Venue: Bukit Timah Shopping Centre unit B2-13C MCQ and Data-based organic questions will be covered under part 2 of our revision programme. Dates: 21 and 23 June Time: 2 - 5 pm Venue: Bukit Timah Shopping Centre unit B2-13C J1 students, stressed by your first JC major exam? ...
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Tips for Studying Chemistry Let's face it, chemistry is not the easiest subject to master. It's abstract concepts (think atoms and molecules) which you can't see with your eyes. So here i will share with you all 3 tips for studying chemistry. Tip #1: Search for Youtube videos to help you visualize spatial ideas such as atomic orbitals or shape of molecules. #2: Ask your teacher if there's any suitable analogies to help you understand the concept e.g. making Subway sandwich for understanding rate-determing step #3: Play with physical models such as those by Molymod, we happen to have a set here at Khemistry so do drop by if you want use it 🙂 All the best for your Chemistry and ...
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Bukit Timah Shopping Centre Class Timings: JC 2: Saturday, 230 - 430 pm JC 1: Sunday, 2 - 4 pm  Register for your slot today! ...
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