Chemistry
For Chemistry Discussions
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Four identical containers under the same conditions are filled with gases. A: Nitrogen B: Oxygen C: Ethane D : Neon Which container and contents will have the highest mass? ANS: B, Oxygen How do you know which is the highest mass? I thought it is based on the Ar, but I was wrong. Please help me understand the reason why it is oxygen. Thank you
Last reply by Vioh, -
Enthalpy
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Hi there, This is probably an incredibly stupid question but can someone explain what enthalpy is, exactly? I believe it's the change in temperature in a particular system, but reading my textbook it's only description is that it is "a state function". After doing a little more digging, I've just ended up confusing myself entirely. Is it essentially just the above? Thanks!
Last reply by Msj Chem, -
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Can someone please explain the rules for writing equilibrium constant expressions as shown in my book: 1. For an aqueous reaction the concentration of the solvent water does not appear in the equilibrium constant expression as its concentration does not change during the reaction. 2. If the reaction takes place in a non-aqueous solution, water must be included in the Kc expression as any other reactant or product. Please provide examples
Last reply by kw0573, -
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I was going to determine the activation energy but i just found out it was HL content for chemistry but i've already done the experiment and everything?? Can i USE the HL Content??
Last reply by Sandy, -
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Can anyone suggest tips or most effective ways to revise Chem HL during the break? Any tips or advise will be a great help for me. Thank you
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I'm taking Chem SL alone (Our school is really small). Any tips and tricks on how to survive it alone? Thank you soo much.
Last reply by Professional student, -
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Greetings my fellow IB DPs, I am inexperienced at Chemistry and have a 4 in general Chemistry SL, as well as being new to this website I would love some seasoned knowledge from y'all IBees. I need help to find research on how to calculate the exact nitrogen levels in soil. If you may post any pdf documents you know or any personal insights and knowledge I will be very lucky and extremely grateful to you.
Last reply by Professional student, -
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So... I'm taking Chemistry HL. It's about to finish my first year of IB. - I started my revision as I'm almost done with my year of Grade 11. - I realized my teacher didn't cover some parts of the syllabus. We covered up to kinetics chapter, but my teacher didn't make any test for us yet. I realized my teacher haven't even read the syllabus yet, and he basically taught us from his intuition as former AP teacher. ... It seems I have not much choice but learn from Mr Richard Thornley's video on Youtube. It's his first year of teaching IB Chemistry and I understand about his confusion for the curriculum, but I'm wondering about…
Last reply by Professional student, -
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I'm thinking of purchasing a study guide. Is the Cambridge Chemistry for the IB Diploma Exam Preparation Guide a good choice? My textbook is Cambridge and I liked it. What do you think about getting the Cambridge one? Or is there better study guides? I would like a pretty precise one without vague info or irrelevant topics. Thanks
Last reply by inriya, -
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I am in IB1 and I want to major in Engineering and most probably Mechanical E. I take math and physics HL but I don't take chemistry. I also take business and economics in sl. Should I drop business SL and take chemistry instead? Why? Is chemistry that hard to study and get a 6 in? Is it fun or boring and not nice to study? Thank you for the support !
Last reply by MarcoED, -
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0.50 mol of I2(g) and 0.50 mol of Br2(g) are placed in a closed flask. The following equilibrium is established. I2(g) + Br2(g) IBr(g) The equilibrium mixture contains 0.80 mol of IBr(g). What is the value of Kc? How is the answer 64? Should I change the mol into mol dm-3? Thank you.
Last reply by Msj Chem, -
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QS: The rate expression for this reaction is rate = k [N2O]2 and the rate constant is 0.244 dm3 mol–1 s–1 at 750 °C. A sample of N2O of concentration 0.200 mol dm–3 is allowed to decompose. Calculate the rate when 10 % of the N2O has reacted. ANS: 0.9 × 0.200 = 0.180 (mol dm–3); rate = (0.244 × (0.180)2 =) 7.91 × 10–3 mol dm–3 s–1 Why do we have to times 0.9 to 0.200? I thought since 10% has reacted, 0.1 should be times instead of 0.9. Please help me clarify this question. Thanks alot
Last reply by kw0573, -
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Can you please suggest some revision guides or study guides that are the most effective? And where can I get the syllabus that states all the specific things that I should know? like those 1.1.1 and stuff. Thanks in advance!
Last reply by IB`NOT`ez, -
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1. At 25 °C, 200 cm3 of 1.0 mol dm–3 nitric acid is added to 5.0 g of magnesium powder. If the experiment is repeated using the same mass of magnesium powder, which conditions will result in the same initial reaction rate? Volume of HNO3 / cm3 Concentration of HNO3 / mol dm–3 Temperature / °C A. 200 2.0 25 B. 200 1.0 50 C. …
Last reply by allthebest, -
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I saw some people making syllabus notes based on each point on the syllabus. It was like "7.1.1 Outline the characteristics of chemical and physical.." followed by 7.1.2 and so on. However, I could not find them in the syllabus. All I could find were "7.1 Equilibrium" with several bullet points under Understandings. Anyone know where I can get those specific 7.1.1? Please help me. Also, any tips when making own notes with syllabus? Thanks in advance
Last reply by ChocolateDrop, -
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So for my IA I wanted to determine whether or not the affect of different temperatures affect the solubility of Sodium Hydroxide. My teacher did not say anything about the IA but when I did some research online I found out that it is extremely dangerous to add Sodium Hydroxide in boiling water and now I am worried and Idk whether or not I can continue with my IA. I also have another problem, I'm not sure whether or not this topic is already a prescribed experiment because if it is then I can't do it. Please help!
Last reply by kw0573, -
Hello, 1. Why is Kc only effected by temperature and not pressure/volume and concentration? shouldn't Kc decrease for example say if volume is increased in the Haber process and equilibrium shifts to the left so Kc is supposed to decrease as concentration of reactants increases whereas concentration of products decreases?
Last reply by kw0573, -
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Is this possible? I just did half an IA on this and its due tomorrow. Basically, I changed the concentration of the HCl because the H+ ions in HCl catalyse the reaction, therefore by changing the concentration the amount of catalyst changes. I then used the same moles of sodium thiosulfate and timed how long it took for the sulfur to form. I'm trying to figure out how to use the Arrhenius equation and i'm really stuck. I basically found the ln 1/t (seconds) which is apparently equal to ln K (plot on the y axis) and 1/T (kelvin) plotted on the x axis and plotted it iwth all my different concentrations, but apparently I need to plot the same concentration but just at d…
Last reply by abelkoontz, -
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When reacting sodium thiosulfate with a more concentrated HCl solution, will the temperature rise faster than a lower concentration of HCl or will it be slower?
Last reply by abelkoontz, -
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Hello, This question is for the decomposition of hydrogen iodide: 2HI <------> H2 + I2 I managed to answer the question correctly, however i'm not sure if the way I interpreted the question may have been correct, I would appreciate it if you could confirm whether my approach was correct or not. For experiment one, I assumed that the concentration of HI would decrease by x at equilibrium (0.06 - 2x) and both [H2] and [I2] would increase by x at equilibrium (0.00 + x), as I have been given the concentration at equilibrium for H2, I substitute it in x and find the values for the concentrations at equilibrium of reactants and products to calculate the Kc …
Last reply by Msj Chem, -
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1. Why does CH3COOH have a higher boiling point than CH3CH2OH, don't they both form hydrogen bonding, what else is a determining factor? Is it the molar mass as the greater the molar mass the more electrons and the increased polarisability so the stronger the London dispersion forces? 2. What intermolecular forces does van der Waals' forces cover (I get different interpretations from different sources)?
Last reply by Msj Chem, -
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Hello, Can you explain how to answer the following questions? the answer for 23 is D and the answer for 22 is A.
Last reply by Emmi, -
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Hello, for my chemistry IA I'm measuring the effect of different pH on the colour of minced beef. To do that I'll crush the beef using a pestle a mortar. I'll then add a bit of water and measure the colour of the resulting solution using a colorimeter. Is this procedure viable enough? Thanks.
Last reply by lance mk, -
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Hello, Can someone explain why the answer is A? I understand why the others are wrong, but can't seem to grasp why it's 1/4th CF4 and C, please explain. ,
Last reply by kw0573, -
Hello, 1. Considering the fact that the formation of bonds releases energy, do stronger bonds release greater energy than weaker bonds, hence why the greater the charge and the smaller the atomic radius the greater the magnitude of the lattice enthalpy? 2. What type of bond is formed during hydration such as when NaCl dissolves in water and the ions are separated from the crystalline lattice by the partially charged atoms in the water molecule, what type of bond is formed between the ions and water molecules?
Last reply by Msj Chem, -
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Hi, Would anyone know of some resources I could use to study Option A? In particular, the various spectrums and HNMR spectroscopy? Thank you!
Last reply by Msj Chem, -
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So my research question was to determine activation energy of HCl and Sodium Thiosulfate, but I changed the concentration of Sodium Thiosulfate instead of the HCl -- I just found out that the H+ ions in HCl catalyse the reaction???? IM NOT SURE WHAT TO DO !!! HELP OH MY GOD
Last reply by abelkoontz, -
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So i think I did the whole thing wrong I changed the amount of moles by diluting the solution however I used the same volume of 40 mL (used 40ml for 1 mole, 30ml for 0.75 moles, 20 ml for 0.5 moles etc) but through calculations the concentration stays the same e.g moles/volume = concentration, 1/40 = 0.025, 0.75/30 = 0.025 mol.dm3. So what exactly was my independent variable?? Please help omg
Last reply by kw0573, -
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ok im in my final year (nov exams 2016) and i have to find a topic for my HL chem ia. i didnt do experimental which means i am now doing theoretical and i need some ideas. i like organic chem the most, but am willing to do some of the harder topics if it means ill have to revise. i am currently on a 3, but am aiming for at least a 4/5 so i want the ia to boost my mark so not too simple but not too hard. id appreciate any help
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I'm determining the activation energy of the reaction between sodium thiosulfate and HCl. I just wanted to check if i was doing the experiment right I have 3g of Sodium thiosulfate solid and add it to 10ml - 20ml of HCl I'm changing the concentration of HCl but online i found that people changed the concentration of the sodium thiosulfate. I dont have sodium thiosulfate in liquid form what do it do??
Last reply by kw0573, -
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Please help me with this question: Propan-1-ol and hexan-1-ol are both alcohol. State and explain which compound is more soluble in water. I said that propan-1-ol is more soluble, but I don't know the exact reason. Is it because it is lighter? I think it has something to do with the intermolecular forces of the alcohols and the water. Thank you
Last reply by Msj Chem, -
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20 cm3 of ethyne, C2H2 are reacted with 500cm3 of oxygen. The equation for the reaction is 2C2H2 (g) + 5O2 (g) --> 4CO2 (g) + 2H2O (l) what is the limiting reactant? My answer is C2H2 with 0.000417 mol Is this correct?
Last reply by Msj Chem, -
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When drawing the born-haber cycle for sodium chloride, the values that are given are: atomization of Na and the enthalpy change of formation. How can I find the other values in the formula booklet? which table should I use? for example, for: Na (g) + 1/2 Cl2 (g) becoming Na+ + e- + 1/2Cl2 (g) thank you.
Last reply by Msj Chem, -
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So I was wondering if all Chemistry EE questions have to be in the form What(independent variable) affects what(dependent variable)? Can it simply be something like' an investigation into the properties of a substance'? or modelling so and so?
Last reply by AnjaDe, -
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Is the IA graded differently for SL and HL? Should HL choose "harder" topics than SL?
Last reply by Rosalina, -
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Hey Guys... So I was wondering how feasible a Computational Chemistry Extended essay would be? Does my extended essay need to have experiments and primary data? Thanks
Last reply by AnjaDe, -
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hello everyone, I recently finished my chemistry 2016 exams and only realized after I came out of the examination room that I wrote outside the answer boxes. Although I did not exceed the boxes very much, only by maybe 2 cm max, do you think my answers will not be scanned?
Last reply by Steven Nanda, -
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I finished my chemistry test last week. Some chemistry options very closely related to Bio or Physics, so I heard that many students had a conflict in the school on choosing which option to study. In my school, my teacher just gave us a freedom to study the option that we are most interested/best in. As I took Bio, I took Biochem and some of my friends who took Physics took Option C. However, my teacher made Option B students self study while he taught Option C students for two months. I guess it's fair because even though I was Bio SL, more than 70% of the Biochem didn't have much new stuffs for me. How did you guys choose the option. Did your teacher force you to make a…
Last reply by inriya, -
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Hey, I am currently in the process of my chemistry IA. I have chosen a subject that I was interrested in which was the change of a flame's color depending on the salt. The procedure involves me lighting a bunsen burner and afterwards spraying 7 different liquid salts onto it and observing the change in color. The problem is that with a simple experiment like this, I am afraid of not having enough data. The salts I used were: KOH - orange/yellow KCl - Orange/purple/yellow HCl - orange/yellow HNO3 - green Na2SO4 -yellow/orange CaCl2 - yellow/orange H2SO4 - yellow/orange Is there any qualitative data tha…
Last reply by AnjaDe, -
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Hello, Does anybody have the list of the practicals that we were required to do for Chemistry fro Paper 3? Thanks! P.S. I know some people say there aren't any required practicals but as there are for Physics and Biology I assume there is as well for Chem...
Last reply by charco, -
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Hey do any of you know where I can find practice question for option C? So far I've only done the specimen paper and questions from the oxford textbook. Also are there any data analysis tips/tricks I should know about for paper 3? Thanks!
Last reply by thestruggleisreal28, -
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Hi there, I was wondering if anyone could help me with this question since I have no answer key whatsoever. Identify the limiting and excess reagents for each of the following pairs of reactants, and determine the chemical amount in excess in each case. a) Cl2 (aq) + NaI (aq) -----> 10 mol 10 mol b) AlCl3(aq) + NaOH(aq) -----> 20 g 20 g I was able to determine limiting reagents in a and b ( NaI and AlCl3) but am not sure what the chemical amount is or how to get it. Some clarification would be great Thanks in advance!
Last reply by Msj Chem, -
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Guys, does it matter if I answer CH3CH2OCH3 instead of CH3OCH2CH3?
Last reply by IBdoingnothing, -
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Hey! So, I am doing some stoichiometry, but I realized that he was using L, whereas in IB, we use dm^3. In the video linked, he converts the amount using a conversion factor, Would this step change, since we are using dm^3, or do I basically just do what he is doing (except for using L)? - It is around (5:00 he does the conversion)
Last reply by Msj Chem, -
- 3 replies
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Hello there! I'm currently an IB1 Chemistry student who has his finals fast-approaching, so I would appreciate it if you could answer the following question with explanation. Answers: 3. B 9. C 15. B Thanks,
Last reply by kw0573, -
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So a toxic gas A contains 53.8% nitrogen and 46.2 % carbon. At 273 K and 1.01 x 10^5 Pa, 1.048 g of A occupies 462 cm^3. Determine the empirical formula of A, calculate the molar mass and determine the molecular structure. I have trouble determining the molar mass. When I do it, I end up getting around 5.094 g/mol but accordingly the answer is supposed to be 51.9 g/mol. How do you get the latter answer?
Last reply by Msj Chem, -
- 0 replies
- 391 views
So a toxic gas A contains 53.8% nitrogen and 46.2 % carbon. At 273 K and 1.01 x 10^5 Pa, 1.048 g of A occupies 462 cm^3. Determine the empirical formula of A, calculate the molar mass and determine the molecular structure. I have trouble determining the molar mass. When I do it, I end up getting around 5.094 g/mol but accordingly the answer is supposed to be 51.9 g/mol. How do you get the latter answer?
Last reply by Zangetsu, -
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So originally I thought when you are doing electrolysis, for the aqueous solutions, you always consider between H+ and the metal cation ? So for both of the solutions, hydrogen gas should be discharged preferentially due to a less negative E value number? But why is the answer comparing it to H2O??? Please help
Last reply by kw0573, -
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Why does pcl5 hv higher melting point than pcl3? I understand that it is cuz it has greater mass/greater number of electrons, hence greater london force, but can't it not equally be argued that pcl5 is non polar because its trigonal bipyramidal and pcl3 is polar and so, theoretically PCl3 should have a higher melting point? Please advise.
Last reply by inriya, -
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Hey! I was wondering what people were tested in: we were tested in the specimen papers! (for chemistry HL mocks 2016 prep for may exams 2016)
Last reply by Elc,
