Chemistry
For Chemistry Discussions
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I would REALLY appreciate some full explanation for this question. The thermal decomposition of sodium hydrogen carbonate, NaHCo3, results in a 73.8% yield of sodium carbonate, Na2Co3. 2NaHCo3=Na2Co3+H2O+Co2 If a 1.68 g sample of sodium hydrogen carbonate is heated, calculate the mass, in g, of sodium carbonate produced.
Last reply by Turquoise_96, -
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- 611 views
Hi guys, so my teacher assigned a design lab topic as "Design a lab investigating the properties of aggregates". I understand aggregates are substances that result from different bonds, but i'm confused as to how to come up with a design lab investing their aggregates. Only thing I can come up with is via different tests such as melting point, conductivity and solubility determine the type of aggregate. Do you guys think this will work? or am I totally off track here, do you guys have any ideas? thank you!
Last reply by Jesus, -
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I'm a junior, and my IOP is coming up this December... I have no idea what the purpose of the IOP is, and I was wondering if it really affects your overall IB score? Do you guys have any tips on how to do well?
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Hello, I have a design lab due very soon on electrode potential. What are the independent variables I can use? Please I need help
Last reply by Megamind, -
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I want to do my IA on how pH affects the rate of a reaction, and ideas on what reaction i could use where i could easily change the pH. Also how would i change the pH?
Last reply by emzinger, -
IB Chemistry HL Salt Hydrolysis Design Lab (acids and bases)
by Guest Joon Cha- 2 replies
- 3.2k views
I need to do the salt hydrolysis design lab. I firstly thought of how does temperature affect the conductivity of the deionized water with NH4Cl salt? but that was already taken. I also thought about "how does temperature affect the pH of the deionized water with NH4Cl, but that does not work as well.... but that was also taken I have no idea what to do on the salt hydrolysis, when I searched, all they give was "investigate different salt and their pH, but that's not quantifiable and cannot be expressed in graphs. I then come up with "how does concentration of NH4Cl salt affect the pH" but my teacher said it can be "mathematically calculated". Could you give me so…
Last reply by by.andrew, -
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Someone please help me choose an efficient lab report topic for my IA.....Thnxx~Chirag
Last reply by Emmi, -
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Hi, Is there a specific website where I can find practice questions for each unit for HL Chemistry (Units 1-12), separately? By separate, I mean so that the questions for each unit are not mixed, but are separate. I find them scattered all over the internet, so it's hard to go back and forth. If there is a website where I can find a bunch, that'd be great to know. Thanks!
Last reply by Luleline, -
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I would REALLY appreciate some full explanation for this question. The thermal decomposition of sodium hydrogen carbonate, NaHCo3, results in a 73.8% yield of sodium carbonate, Na2Co3. 2NaHCo3=Na2Co3+H2O+Co2 If a 1.68 g sample of sodium hydrogen carbonate is heated, calculate the mass, in g, of sodium carbonate produced.
Last reply by Acorn_brain, -
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A solution of 155 g of potassium iodide, KI is added to a solution of 175 g of nitric acid, HNO3. The acid acts as an oxidizing agent. 6KI + 8HNO3= 6KNO3+2NO+3I2+4H2O A) Deduce which reagent is in excess. B) Determine how many grams of this reactant will remain unreacted. C) Determine how many grams of nitrogen monoxide, NO will be produced.
Last reply by Acorn_brain, -
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Hi everyone, if someone could please explain the following question's process to solving the answer it would be highly appreciated 1. Potassium superoxide, KO2, reacts with carbon dioxide, CO2, to produce oxygen and potassium carbonate, K2CO3. Write the balanced equation for this reaction (I already did this- 4KO2+2CO2=3O2+2K2CO3). 28.44 g of KO2 reacts with 22.00 g of CO2. Deduce the limiting reagent, calculate the mass of K2CO3 produced as well as the mass of O2 produced.
Last reply by Emmi, -
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Hi, I would really appreciate some clarification on whether or not I executed the correct process for the following question: Ethyne, C2H2, reacts with oxygen according to 2C2H2+5O2=4CO2+2H2O. What volume of oxygen, in dm3, reacts with 0.40 dm3 of C2H2? Initially, I recognized the ratio of ethyne to oxygen to be 2:5. Then, I cross multiplied 2/5=0.40/x. I received the answer as 1 dm3. Is this correct?
Last reply by Emmi, -
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Hi everyone, I would really appreciate some help in solving the following question. I did the process but I wanted to ensure that I achieved the correct answer. Thank you Two aqueous solutions, one containing 5.3 g of sodium carbonate and the other 7.0 g of calcium chloride, are mixed together. A precipitation reaction occurs: Na2CO3+CaCl2=2NaCl+CaCO3 Determine the limiting reagent and the mass, in g, of precipitate formed (theoretical yield).
Last reply by daniaridha, -
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If you could please help explain the process of how to solve this question, that would be greatly appreciated 1. Butane lighters work by the release and combustion of pressurized butane. 2C4H10+13O2=8CO2+10H2O Determine the limiting reagent in the following reaction. a) 20 molecules of C4H10 and 100 molecules of O2.
Last reply by Msj Chem, -
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I was wondering if anyone would be able to fully explain the following question: Ethyne (C2H2), reacts with oxygen according to the equation below. What volume of oxygen (in dm3) reacts with 0.40 cm3 of C2H2? 2C2H2 (g) + 5O2 (g) --> 4CO2 (g) + 2H2O (g) Thanks!
Last reply by msingla, -
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I'd really appreciate it if someone could fully explain to me the following question, Calcium Carbonate decomposes on heating as shown below: CaCO3 --> CaO + CO2 When 50g of calcium carbonate are decomposed, 7g of calcium oxide are formed. What is the percentage yield of calcium oxide? Thanks!
Last reply by Aninda Saha, -
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Hello, I'd really appreciate it if someone could fully explain to me the answer for the following question: Epsom salts (magnesium sulfate) are commonly used as bath salts. However, the anhydrous form of the salt is a drying agent. To determine the water of hydration of Epsom salts, a 2.50g sample of the salt was placed in a porcelain evaporating dish and gently heated over a Bunsen burner flame until no further changes were observed. Below are the results: Mass of evaporating basin = 24.10g Mass of evaporating basin + MgSO4.xH20 = 26.60g Mass of evaporating basin after heating = 25.32g a) Calculate the mass, in g, of water evaporated from the sample b) Calculate …
Last reply by msingla, -
- 5 replies
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If someone could please help me with the following question, that would be great You don't necessarily need to tell me the answer, if you could just explain the process it would be very helpful. Thanks! Silicon tetrafluoride (SiF4) is produced from the reaction of silicon dioxide (SiO2) and hydrofluoric acid (HF) with water as the other product. Write the chemical equation for the above reaction (I already did this, and I got SiO2+4HF=SiF4+2H2O). Please tell me if this is wrong). What mass of silicon tetrafluoride can be produce from 15.00 g of silicon dioxide in 15.00 g of hydrofluoric acid?
Last reply by Msj Chem, -
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If someone could please help me answer this question, that would be great. I am really just trying to learn and understand this process. 1. Acetylsalicylic acid, also known as aspirin, C9H8O4, is synthesized by reacting salicylic acid, C7H6O3, with acetic anhydride, C4H6O3. C7H6O3+C4H6O3=C9H8O4+C2H4O2. a) Calculate the theoretical yield, in g, of aspirin when 3.0 g of salicylic acid is reacted with 4.0 g of acetic anhydride.
Last reply by daniaridha, -
I recently purchased a Texas Instruments 36X Pro, and there are some very enticing features that come with it, some of which I feel like are probably major time savers for some of the calculations you would do in Chemistry. So I'm just wondering if this calculator is 100% allowed and approved for any and all classes and IB exams.
Last reply by Thrashmaster, -
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Hello IBers, I need help on some things about my chemistry lab: - Let's say I'm measuring how temperature changes over time in a reaction between HCl and Na. Do I have to include an uncertainty for my time? By the way, I was using a vernier lab quest to record this data. - Also, on logger pro, how do I add error bars for my data points using the uncertainty of the temperature probe used in the experiment? I know that the uncertainty of the probe is +/- 0.2 degrees celcius, however, I'm not too sure how to add error bars that also consider the standard deviation. Help would be much appreciated! :)
Last reply by khimberleigh, -
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Hi guys, I'm having trouble coming up with ideas for my lab. I'm really not all that creative, so I've been stressing about this. My teacher had given me an idea, but when I tried it, it completely failed, and now I'm extremely discouraged. I really don't know what to do. The lab has to be related to ionic compounds or covalent compounds. It obviously can't be too simple as well. I had originally wanted to measure the colour of a compound after changing it's concentration, but that was too simple. My teacher gave me the idea to use chlorides from group 2 in the periodic table, measure their pH and then their conductivity, but the reason it didn't work was …
Last reply by ouribjourney, -
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Hi guys, I started HL Chemistry this year, so I'm writing my exam for it in 2016. As everyone is aware, the syllabus has changed for 2014, and so all students writing their exams for HL Chemistry in 2016 will write the exam in accordance with the new syllabus. I just wanted to know how hard is it to get a 7 in HL Chemistry overall as my final IB mark in the subject (not a predicted 7, an actual 7)? No one in my school has gotten a 7 so far in HL Chemistry, plus my HL Chemistry teacher is terrible! When I say terrible, I literally mean terrible. He cannot teach at all. Literally, our class ends up teaching each other, or ourselves after each lesson. This means I'm at a g…
Last reply by Vioh, -
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Hey, I'm quite confused right now, because in the syllabus guide it says in the AHL portion of kinetics that we are required to "determine the activation energy values from the Arrhenius equation by a graphical method". And there's nothing about Half-life calculations mentioned in the entire syllabus. However our teacher is pretty much forcing us to solve pretty complicated looking problems about Half-life and activation energy without graphs. And it's explicitly mentioned in the syllabus that such problems will not be assessed. So what now? I have a test tomorrow and i'm pretty sure she'll ask some of that stuff that i'm absolutely not prepared for. Did anyone else ha…
Last reply by Msj Chem, -
- 1 reply
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I have chosen to do a different option than the rest of my class, as I do not at all care for Human Biochemistry, but on the other hand find Medicine and Drugs very interesting. I think I have everything mostly under control for my self study, but my teacher told me that I need to do an experiment within the topic. As we are not allowed to use the lab, it has to be a simulation. I don't have to do an IA on it, fortunately, but I am having some trouble finding simulations for the option at all. Therefore I was wondering if any of you had some links to some simulations that I could use. Thanks in advance.
Last reply by CriCri, -
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Hi, So basically right now the unit we're doing is "Isotopes" and as of now we've only got 2 types of Isotope problems: 1) We're given the abundance of each isotope and asked to find the average atomic mass. For example, Si-28 (92.23%), Si-29 (4.67%), and Si-30 (3.10%). Using that info find the average atomic mass for silicon? 2) We've given the mass of each isotope and the average atomic mass, and asked to find the abundance of the isotopes. For example, Rb-85, Rb-87, average atomic mass- 85.47u, what are the abundances of the isotopes? I understand how to do the 1st style of questions, when asked to find the average atomic mass given the abundances, however …
Last reply by Mathemagician, -
- 3 replies
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Would be really, really, really helpful! Thanks!
Last reply by Magician, -
- 3 replies
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I've recently just started my second year of IB, and realised i chose all the wrong subjects. I'm doing: English Lit HL, History HL, Biology HL Maths SL, Italian SL and Art history SL. I really want to change Art History to chemistry SL as I really want to study Biology at university, and i do it HL, however almost every university i've looked at asks for a second science, at least at SL. I did my Chemistry GCSE and achieved a grade A, and i'm quite a strong biology student. I will get private tuition in chemistry twice a week if i make this change, and work extremely hard. So if i work extremely hard, and get private tuition, is chemistry SL possible in one year? thanks
Last reply by IBidiot, -
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Hi, just wondering whether anyone taking the November 2014 exams would be interested in bonding together to have a chemistry revision group (e.g. Facebook, Skype, etc.). Thanks.
Last reply by apple_cider, -
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Hey guys, So one of my options for Chemistry HL is environmental chemistry. My teacher basically forced it upon us and i don't really mind (I'm happy it ain't Further organic, haha). For the second option I've narrowed it down to either Human biochemistry or Medicine and drugs. Now, I've gone through both syllabi and would really really love to take Medicine and drugs, but since I'm a biology HL student, Human biochemistry seemed easy as pie. so now I'm stuck between choosing something I'd love learning about and something I could easily finish in like 2 days time. Any advice on which one to take would be appreciated because I'm pretty damn confused right now. Cheers!
Last reply by Msj Chem, -
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Hey all, In second year of DP and my IA's are terrible. I would appreciate if someone with experience would be willing to look over my titration to find the 'crystalizzation of water'. I hope its not too much to ask, but these IA's are letting me down and I'd love you if you could invest a little time to give me some feedback:) Thank you, - Phil
Last reply by Ossih, -
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Hi guys I've looked on line a lot and I still don't understand what Gibbs free energy IS. I get that G = H - TS and delta G = delta H - T delta S. Ive also read that its the maximum non-expansion work. First question, what is non expansion work? What kindsfof work count as non expansion? Second, how can I get from Stotal = Ssystem + Ssurroundings to delta G = delta H - T delta S? Any answers would be greatly appreciated
Last reply by Ossih, -
- 6 replies
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Hello, I am already taking Biology HL and I was wondering if, as the 6th subject, it would be useful to take Chemistry SL. I'm not sure what I want to study yet at university, and I know that for most science undergrad courses Chemistry HL is required. I just think doing it HL would be too difficult and could lower my score. Is it really as hard as people say? Now I am undecided between a second foreign language or Chemistry SL. Is Chemistry SL difficult? Thanks
Last reply by Knight, -
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Hi, I'm currently doing an DCPCE IA for kinetics and I'm a bit confused So the aim is ' to investigate the rate of this reaction as a function of the sodium thiosulfate concentration.' Basically in the experiment we took different sodium thiosulfate concentrations, and a constant amount of HCl and reacted them. We then timed how long it took for us to be unable to see the bottom (colour change). So to find the rate of reaction, do I use 1. (rate = 1/time) or 2. (rate of reaction = - change in reactant concentration/time taken) or 3. (rate = k [A)mn)? I'm thinking that I don't use 2. because I don't have the change in concentration, as I only timed how long the reac…
Last reply by crappingmyself, -
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Hey everyone, I am doing SL chemistry I am really struggling with moles. So I was wondering if anyone had any great resources (e.g. online work sheets) that could help me or any advice with how to study for this topic. I pretty much need help with the whole topic! Thank you, it's appreciated!
Last reply by mechnight, -
- 1 reply
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I know when you perform a classic iodine clock reaction, the reacting solution is meant to turn blue-black. However, when I performed it... not only did it not turn blue black, but instead--- brown?! In my experiment, I added two different solutions: Solution 1 contained: 20mL of a reacting solution (1.5g of KI added to 1.9g of Na2S2O3 in 250cm3 of water) 10mL sulfuric acid (H2SO4) 2mL of dilute starch solution Solution 2 contained: Distilled water Variable volumes of hydrogen peroxide (H2O2) Did I do something wrong? I've processed the data that I've collected, and my trends are looking fine, however I just don't know why my solution turned brown-black instead…
Last reply by Ossih, -
- 1 reply
- 860 views
Hi all, So I've recently been trying to calculate the rates of reaction, but I've been slightly confused as to how I should go about it. Should I use this equation: rate of reaction = 1 / t (t is time in minutes) OR rate of reaction = concentration of reactant / time taken for reaction to occur Thanks in advance!
Last reply by Ossih, -
- 1 reply
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Hi, I have a question about a lab I'm designing. I was hoping to do something on testing the alcohol percentage in alcoholic drinks through oxidation and stuff. I think I'll be able to get all my equipment and substances but I'm just worried that the IB might prohibit students to work with alcoholic drinks. Does anyone know anything about this? Thanks in advance!
Last reply by flinquinnster, -
- 2 replies
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My chemistry teacher has been teaching us about propagation of error. She thought us that if we sum c=a+b, then Δc=sqrt(Δa^2+Δb^2).(this is according to our Oxford Chemistry Textbook for 2016 syllabus) However, in my physics class, my teacher thought us that if c=a+b, Δc=Δa+Δb. (this is supported by the data booklet.) I've done a research on the internet and found that the former uses standard deviations while the latter uses simpler average errors. So, what should I do with the uncertainties when I sum a and b?
Last reply by Vioh, -
- 4 replies
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Hello, I'm thinking off choosing Chemistry HL for IB next year because it's necessary to study medicine. I find chemistry really hard and very challenging... Does anyone have any experience with Chemistry HL? Thanks xx
Last reply by Emmi, -
- 3 replies
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Hi All, So, I've been recently working on a prac involving how the rate of reaction (between Magnesium and Hydrochloric acid) can be affected by increasing surface area of the Mg ribbon. And, whilst I don't have any issues discussing the prac itself and the results it produced, I haven't been able to find any literature values at all. I've really tried looking everywhere, and I've only gotten as far as finding a website which showed me some values for varying HCl concentration, not Mg surface area (by cutting up the ribbon into different pieces). And as much as I'd like to, I can't base my prac on varying concentration, since that was the other prac that I did that …
Last reply by by.andrew, -
What does utilization in the subject guide mean?
by Guest Aniruddh- 0 replies
- 524 views
Hey Guys, I have started making my notes based on the syllabus, and I was wonder what does the utilization column on the subject guide mean? Is it just a reference to the applications of the topic we are studying so that the student can dig deeper, or will the questions asked be based on those applications? Please help me out. Thanks, Aniruddh
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Hi everyone, this IA which involves me figuring out the following uncertainties is due tomorrow, but I'm not sure how to do it correctly, I'd really appreciate some help. So here it is: We were diluting 3.0M HCl to various concentrations for a reaction with magnesium ribbon. Our method is terrible I know that, but what I need help with is figuring out my uncertainties. The steps taken to dilute 3.0M HCl to 0.5M were this: With a pipette (uncertainty of ±0.3mL), 3mL of 3.0M HCl was put, with one squirt, into a test tube.Then, to dilute it to 0.5M, we put 15mL of water into the same test tube (which took 5 squirts, pipette with the same uncertainty).We shook the test…
Last reply by thedudeo, -
- 4 replies
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Hi everyone, can somone please help me work out this question: "Calculate the total number of oxygen atoms in 3.2g of S02" Thankyou.
Last reply by mr_awesome, -
- 2 replies
- 943 views
Hey guys! I was wondering if buying the dot point chemistry book was worth it? Thanks
Last reply by Anne Hindenberg, -
- 2 replies
- 903 views
I was doing a QB question, but I don't understand this one. "When 100cm^3 of 1.0 mol dm^-3 HCl is mixed with 100cm^3 of 1.0 mol dm^-3 NaOH, the temperature of the resulting solution increases by 5.0C. What will be the temperature change, in C, when 50 cm^3 of these two solutions are mixed?" A) 2.5 B) 5.0 C) 10 D) 20 The answer given was B, but I don't understand why. I was hoping someone here could explain it to me. Thanks in advance
Last reply by Ossih, -
- 2 replies
- 3.7k views
Hi everyone, where can I access the Chemistry syllabus for the upcoming year. (2014-2016)
Last reply by Msingh_G, -
- 3 replies
- 4k views
I was doing some summer work given by my chem teacher to help prepare us for chemistry class starting in september. I need help with this question: "Rubidium has only two isotopes in nature: 85Rb and 87Rb. Calculate the percentage abundance of the isotopes of rubidium given that the relative atomic mass (weighted average) is 85.47." How would you calculate this? Thank you.
Last reply by Msingh_G, -
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- 683 views
Hi people! Is it worth getting a study guide, revision guide or course companion for Chemistry HL? If yes which of them? Thanks!
Last reply by by.andrew, -
I'm worried
by Arnau- 10 replies
- 1.5k views
Ok, so a few days a go, me and my classmate started reviewing for a test we had. We took out the Chemistry Guide and out of curiosity started looking at all the topics we had covered. We found out we had only covered topic 1 (Quantitative Chem), 2 (Atomic Structure), a part of 3 (Periodical Properties), 12 (Measurements) and Option E (Environmental Chem). We are both in an HL class, so we have all of the core topics plus the AHL topics left, plus our second option, Analytical Chem. We are basically at the end of our first year and the amount of stuff we still need to cover is huge. Plus, we should have some time to take practice tests and to do the IA. Is this a normal th…
