Chemistry
For Chemistry Discussions
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Is Br --> Br2 exothermic or endothermic?
Last reply by Msj Chem, -
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So, as we all know, paper 2 is worth 40% of Chem SL. Leading up to my paper 2 mock, I was pretty confident. I had 6+ on my IA, P1 mock and P3 mock. Then came P2 and I got a 3. At this point, I would be happy with getting around 25-30/50 on P2.. Any tips on how to maximize my points on P2. I still have time to study and relearn some concepts, since the exam is next Thursday.
Last reply by Msj Chem, -
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Last reply by Professional student, -
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A pure aluminium block with a mass of 10 g is heated so that its temperature increases from 20 °C to 50 °C . The specific heat capacity of aluminium is 8.99 × 10–1 J g–1 K–1. Which expression gives the heat energy change in kJ? A. 10 × 8.99 × 10–1 × 303 B. 10 × 8.99 × 10–1 × 30 C. ( 10 × 8.99 × 10–1 × 303) / 1000 D. ( 10 × 8.99 × 10–1 × 30) / 1000 The answer key says its D. I thought it was C. Why is it D? using the formula q=mc∆T the ∆T will be 50-20 = 30 'C and change to Kelvin so 273+30 = 303K so isn't it 10 x 10 × 8.99 × 10–1 × 303 J and to change it to kJ I need to divide by 10…
Last reply by allthebest, -
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For chemistry, I realize that I tend to have difficulty in observable changes of primarily halogens such as colour changes for example. What is a good way or a good source to remember what the changes are in a chemical reaction?
Last reply by Zangetsu, -
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I'm an SL Chemistry student, and I'm pretty decent in chem so I don't mind doing a difficult experiment (the only reason I'm not doing HL is because I'm hoping to enter a more humanities based field.) The thing is, because I'm hoping to become a diplomat instead of a scientist, I'm really struggling to come up with a potential personal engagement, however, I found a plausible one. If I do a database IA focusing on drugs (perhaps illegal drugs like cocaine or opium), then I could connect it to my aspirations to work with people to solve global issues as a diplomat and drugs are a huge problem in modern society. I've found a database I can work off of (because I don't t…
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In a practice question I was doing, it says that 10 cm^3 of 0.01 mol dm^3 of HCL is diluted with 90 cm^3 water and the questions ask to calculate the ph. So if I am correct, the starting PH is 2, due to 0.01 mol being equal to 10^-2. 2nd, with the 10 cm^3 of acid being diluted with 90 cm^3 of water, then would that cause the resulting ph to be a value of 3 as the water dilution makes the acid less acidic?
Last reply by Msj Chem, -
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For this question, I chose B, as random error could be due to human error, however, the answer is C. I can understand why it is C, but I don't understand why B is not the right answer. Any advice will be appreciated
Last reply by Msj Chem, -
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Hey all! Chemistry Exam is in less than 20 days this May. IB chemistry is amongst the subjects with the most diverse and heavy content, each interlocking with one another. However, my problem that my teacher pointed out is not being able to use my knowledge in various topics. For example if acids and bases tied up with redox reactions, I will get nervous and not being able to answer as well. How do you revise for IB Chemistry Exam? Do you have any advice for me?
Last reply by inriya, -
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I was doing some past papers, and they often make you deduce chemical equations (especially products) and i realized how bad i was at doing so. Are there any videos where I can learn how to do it well?
Last reply by Msj Chem, -
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Honestly, I spent all day studying and I have mid term tomorrow (predicted grade for uni) and I really can't do Stoichiometry. Every time I think I get it, I don't at all. And its throughout the whole entire course I'm really at math, can you guys offer any tips?
Last reply by Msj Chem, -
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What are the 7 IB practicals that are needed for CHEM SL. We haven't really been told which have been our IB curriculum/regular curriculum. What are the 7 labs we could be tested on for paper 3?
Last reply by RebelliousYoshi, -
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Hey All! I'm doing the Energy option this may in my exam, and as I've been revising I realised that there are a lot of redox reactions to be covered for the rechargeable cells and fuel cells HL topic. I just wanted to know, are we expected to memorise these reactions and be able to reproduce them in the exam or just understand how they work (meaning that we indirectly talk about them or have the equation given and then do some work with it)? Thanks! P.S. @Msj Chem: Thanks so much for your videos! We didn't have too much time to cover the option in school, so I learned most of it using your YouTube videos and my textbook.
Last reply by Msj Chem, -
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Hi, this question was from a past paper, and I got stuck between choosing C or D, I know the electrode potential (E) should be greater than 0. But what i am stuck with is which one is better reducing agent/ oxidising agent, because it doesn't seem like a fair comparison. Usually we would be comparing between Fe3+ and Br-; and then Fe2+ and Br2. Not the mixture of them together. How to approach these questions? P.S. The answer to this question is D Any help would be greatly appreciated
Last reply by kw0573, -
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So recently we did a lab in which we had to investigate the solubility of group 2 hydoxides and find out the max solubility. We had to link it with ionic radius and periodicity. The previous lab which I did, I got a 3.9. I would like to get some feedback before I submit the lab. Can some people look at my lab report and find some mistakes? Thanks for your inputs, I will try to use your feedback. Please ignore some spelling and formation errors in the conclusion & evaluation. solubility lab.pdf
Last reply by kw0573, -
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Hey guys! I need help for my Chemistry SL mock Internal Assessment. I have no idea about what to do and how to do. May you please suggest some ideas about the IA? Thank you in advance.
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The syllabus changed so there were changes to the optionals in HL Chemistry, anyone have questions that the IB/Teachers might ask on tests regarding Paper 3 Option D - Drugs and Medicine? I've already seen the specimen paper btw.
Last reply by Msj Chem, -
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I was doing a past exam paper, and the temperature change was 7 degrees celsius, so I converted it into Kelvin, but the answer had it in celsius. I thought that change in T was always meant to be Kelvin? Is this not the case for ib? thanks!
Last reply by turtle turtle, -
Uncertainty Calculation
by Guest- 1 reply
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A burette reading is recorded as 27.70 cm3 +/- 0.05 cm3. Which of the following could be the actual value? I 27.68 II 27.78 III 27.4 A I and II B I and III C II and III D I, II, III I'm not how to solve this, but I used the total error equation to dtermine which one had less of an error - that would be the actual value and I got C. Not sure if it's right?
Last reply by Msj Chem, -
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So i am working on a lab report related to the use of a colorimeter. So from research it is said that the values are the most accurate from 0-1, acceptable from 2 to below 3. I wonder what does this value mean? E.g. i got 0.9156 for blue absorption. What does it mean then? Thanks!
Last reply by kw0573, -
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The question is this: at 25 degrees C, 200 cm^3 of 1 mol dm^3 of nitric acid is added to 5g of magnesium powder. If experiment is repeated using same mass of magnesium powder, which conditions will result in the same initial reaction rate? I chose 100 cm^3 of nitric acid , 2 mol dm^3 as conc and 25 degrees C. However, the answer is 100 cm ^3 of 1 mol dm^3 HNO3. How is it the case? If it is so, then in 200 cm^3, there would be 2 mol dm^3. As there is a higher conc, then the reaction rate should be higher, so it doesn't give the same rate?
Last reply by Msj Chem, -
Hi, My school has selected medicinal chemistry for the options topic, however, I'm currently struggling with it due to it containing excessive amounts of biology and organic chemistry. I'm doing HL physics and think I would do a lot better at the energy option. Is it possible for me to answer the energy option in paper 3 instead? For maths HL we are only given questions on our option topic and for English we have to refer to the texts selected by our school. However, for sciences I know that the paper 3 contains all topic questions. Would the examiners still mark the questions I've competed even if other students answer on a different topic? Any advice would b…
Last reply by Msj Chem, -
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Edit: SOLVED What is the condensed structural formula of the organic compound that forms when concentrated sulfuric acid is added to 2, 3-dimethylbut-2-ene, (CH3)2C=C(CH3)2, followed by water? A. (CH3)2CHC(OSO3H)(CH3)2 B. (CH3)2CHC(OH)(CH3)2 C. (CH3)2C(OH)C(OH)(CH3)2 D. (CH3)2(CH2)2(CH3)2 I sort of get that the correct answer is B when combining the reacting components together, but is there a better explanation such as its reaction mechanisms? Help is very much appreciated, thanks!
Last reply by Msj Chem, -
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Hi there! I want to ask your opinion regarding my IA Chemistry. My RQ is "Does different type of salt, Nacl, MgCl2, CaCl2, KCl and C2H3NaO2 affects the freezing point of ice by determining the change in temperature using equal amount of salt?" . My 1st issue is : When I analyse the result, I can only produce bar graph since I am using TYPE of salt. My teacher is worried because she said bar graph is not good enough. But I dont understand why it is not good enough..but whatever it becomes a problem to me now. 2nd issue : My calculations is very little which is only to calculate change in temperature..Do you have any idea how I can elaborate on calculati…
Last reply by bguloglu, -
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Edit: SOLVED Which substance has the greatest bond length between the carbon atoms? A. C2H2 B. C2H4 C. C2H6 D. C2Cl4 Answer is C. I get why the bond length of C > B > A due to single bond length > double bond length > triple bond length. However, I have no idea about the bond length of the halogenoalkene. Help is very much appreciated, thanks!
Last reply by Magician, -
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Hey everyone! As the title suggests, the syllabus says that we should be able to discuss "how the choice of fuel is influenced by its energy density or specific energy." I understand that a higher energy density and specific energy means it is an effective fuel, but how about when there's two fuels, one with a higher energy density and lower specific energy versus one with a lower energy density and higher specific energy? Which fuel would be the better choice? I think I can save another post by asking my other question here: For everyone else doing Energy, we are aware that it is a new option and thus it has no practice questions from past exams. How are you guys st…
Last reply by Elite X-Naut, -
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My average grade for Chemistry HL is 7. Trust me, I am not too bad when it comes to written exams. However, my teacher sent me the chemistry IA recently which will be sent to the IB very soon. However, when I read his/her comments, it's very negative. (E.g: The candidate attempted to provide technical errors to satisfy the evaluation criteria. All of these are entirely trivial, they are entirely general and does not reflect anything specific. / MISGUIDED IA) I am not here to blame my teacher, but I am worried right now after reading the whole report. When I have put a lot of my efforts in my IA, the reality is not reflecting anything at all. Now, and I know it is too la…
Last reply by inriya, -
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Hey everyone, as you know there is a new syllabus for the experimental sciences with first examinations starting May 2016. I looked through the IBO website online to see the syllabus changes and I saw something about the NOS. Under "Changes to External Assessment," it states that: Assessment of the NOS may be incorporated into any of the questions in the three examination papers. Throughout the syllabus it seems very vague, but it starts becoming more descriptive in the headings for each lesson, such as: "Concepts—the concept of the mole developed from the related concept of “equivalent mass” in the early 19th century", or "Making careful observations and obtaining eviden…
Last reply by thecsstudent, -
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Hello all, My class is mostly focused on medicine and I'm the only one taking Chemistry HL without Bio HL, and I was wondering if any of you decided on learning an option by themselves? They are all hyped about biochemistry, but I'd rather do Medicine and Drugs, as it seems easier and more interesting to me. What are your experiences with self-learning? Is it possible?
Last reply by Msj Chem, -
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I was wondering if someone knows any source thats really good at explaining moles. Also if you know how to answer this question please explain how: 5.60 x 10^25 atoms of H = _______ mol of H2O.
Last reply by Msj Chem, -
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Q: State and explain whether 0.1 mol magnesium hydroxide is more effective or less effective than 0.1 mol of aluminum hydroxide. I don't know how I would solve this question? Is it related to molar mass, bonds, polarity? I have no clue... Please help me understand how I can solve this question.
Last reply by kw0573, -
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How do you go forward with this question? When the same quantity of electricity was passed through a dilute solution of sodium hydroxide and through a molten soluton of lead bromide, 0.100 mol of lead was produced. What amount (in mol) of hydrogen gas was evolved? A. 0.014 B. 0.050 C. 0.100 D. 0.200 Don't we need the Data Booklet for this one?
Last reply by Msj Chem, -
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Hey science experts out there. So Chemistry really isn't my strong suit, but I do know that generally you do not EVER use personal pronouns in any sort of scientific or academic paper. However, I'm a little confused as to how we otherwise should go in depth with the personal engagement. In the assessment criteria my teacher gave me, it says "the justification given for choosing the research question and/or the topic under investigation demonstrates personal significance, interest or curiosity". What did you guys get, and did your teacher say anything specific for this? Also, I'm a little nervous. My experiment is on electrolysis as a means of removing tar…
Last reply by kw0573, -
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Can someone tell me how many pages can my Chemistry IA have. I was looking at the ChemGuide for 2016 and read that my write-up must be about 6 to 12 pages long. So, basically, I would like to know what is included in write-up? My IA has 11 pages without cover page, content page and bibliography, so when including everything there are 14 pages. Now, I am not sure if this is acceptable. Thank you all!!
Last reply by Msj Chem, -
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Hi everyone:D I am currently working on an IA report concerning the catalyst effect of Fe2+ on the reaction between persulphate ion and iodide ion: 2KI(aq) + K2S2O8(aq) -> 2K2SO4(aq) + I2(aq) and i add Fe(II)SO4 as catalyst My hypothesis is that as the concentration of the Fe(II)SO4 increases, the I2 formed should be increased as well. But as i just had my lab session today, i found that the below results : If i don’t add any catalyst, the rate of I2 forming is super slow If i add 5 ml of 0.1m Fe2+ catalyst, the frequency of blue adsorbent is at around 1.464 at 5 minute mark If i add 5 ml of 0.05m Fe2+ catalyst, the f…
Last reply by FrosciSnowflake, -
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Hi everybody I'm currently in IB2 my exams are exactly two months from today and i need to start revision but when it comes to chemistry i'm completely lost! My aim for the final is to hopefully achieve a 5 (a 6 would be great but honestly i'd be equally happy with a 5 it's all i need for uni) so my question is does anyone have advice on how to achieve this? Do i take notes? read from the book? past paper questions are a must of course. And for those of you who have taken IB before how did you all revise? and did it help you achieve the grade you wanted? any and all advice is appreciated
Last reply by kw0573, -
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I was wondering if it is possible for me to use an HL topic from Chemistry even though I take it as an SL. Is this possible or do I have to have an SL topic for my IA?
Last reply by beatriz, -
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It's late in the year and I don't have time to do a hands on experiment for my internal assessment. Any opinions about using a simulation for my experiment. If yes it can be used how do I write a method, list of materials, and procedure for it?
Last reply by beatriz, -
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I was just wondering if someone was able to help me regarding my chem ia for this year because I'm really struggling and the teacher wants them in!! So basically, we began with him giving us different methods that we could choose from, and I chose "determining the total calcium and magnesium ion concentration of Milk" and I've found this for five types of milk, using titration. How could I use the information that I have to make this into an investigation, i.e.. "How does x affect/determine y?" Please help me, I am really struggling and this is taking up so much time that I could be using on all my other IAs!!
Last reply by beatriz, -
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Please help! I need to find a topic for the Chemistry Extended Essay really soon and I can't find any. I know that I am interested in acid base titrations and maybe green chemistry but I don't know how to formulate a research question and make it more focused and less broad. Thanks.
Last reply by Sandwich, -
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Hi Guys, For my IA I am finding the equilibrium constants of different esters. I cannot seem to find the literature values anyway. Does anyone have a link?
Last reply by Asmita, -
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If I had processed values of: 0.00340 0.00780 0.0100 0.260 0.240 This is an example of something that had occurred in one of my labs. How would I show this in a table? They're all 3 significant digits but, they're not in the correct amount of decimal places.
Last reply by kw0573, -
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Hi guys! So I have my averages and uncertainties for it but some of the uncertainties are different for each condition.. how would I incorporate the +/- unit in my graph as the uncertainties of my averages are not all the same? A quick response is appreciated and thank you for the help
Last reply by Vioh, -
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I have a problem with a graph in a lab report i am doing. This graph has on the Y axis the absorbance of a solution. That data has an absolute uncertainty of 0.001. However, the error bars are very small and can't be seen. Also the line of best fit should "touch" all of the error bars, however on my graph the line does not touch any of the error bars. If I change the value of the error bars to the one of deviation, the error bars appear and the line of best fit goes through all of them. What should I do? Is it correct to put the deviation as error bars? Thanks in advanced!!
Last reply by Vioh, -
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So at my school they offer IB Chem HL, but it goes in for two periods so you're taking HL I and HL II during the same year. I am wondering if it's worth my time to take Chem if its gonna take up that much time in my schedule. I already have my three other HLs (math, english and spanish)... anyone in chem please let me know if it is worth it
Last reply by Sandy, -
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The equation for the reaction between methane and chlorine is CH4(g) + Cl2(g) → CH3Cl(g) + HCl(g) Use the values from Table 10 of the Data Booklet to calculate the enthalpy change for this reaction. wouldnt you do bond breaking - bond making? the answer is 654 – 796 = -115 kjmol-1 where do you get 654 and 796 from?? i hate chemistry Given the following data: C(s) + F2(g) → CF4(g); ∆H1 = –680 kJ mol–1 F2(g) → 2F(g); ∆H2 = +158 kJ mol–1 C(s) → C(g); ∆H3 = +715 kJ mol–1 calculate the average bond enthalpy (in kJ mol–1) for the C––F bond. (4) how
Last reply by Msj Chem, -
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I have 30% conc of hydrogen peroxide and I need to reduce till 3% by using water HELP!
Last reply by azara, -
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So, I have somewhat an idea of what id like to do involving my chemistry IA but I'm in need of an opinion and or suggestions. My idea is an experiment testing the affects of Carbonic acid (due to ocean acidification) on shelled organisms and others that use calcium carbonate. Perhaps testing at which concentration it is harmful? I dont have a specific or elaborate idea and am struggling to think of one all i know is that this topic is important to me and the world itself. All suggestions welcome please!
Last reply by Siddhakshi, -
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I always wonder whether it's possible to remove/prevent rusting on metal. I searched online and found that salt can decrease the oxygen concentration in water. With decreased oxygen concentration it would be harder for rusting to occur. But why are rusting for metal parts of ships occurs even more frequently? (since sea water should have a high salt concentration). That leads me to my IA topic: The relationship between rate of rusting and salt concentration. (pending only). As i dig deeper, I found that rusting usually takes a long long time to occur. Is there a way to increase the speed of rusting? Furthermore, I am considering measuring the weight of rust formed by…
Last reply by kw0573, -
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this is my first time and i thought of this research question. "How acidic are different types of canned coffee" is it okay or is it too dumb? cuz it sounds too dumb but i cant think of any other stuff thats not dumb. any brief suggestions of RQs? thanks;)
Last reply by kw0573,
