CHEMISTRY COMMUNITY

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What does it mean when something is at zero, first, or second order? Also how do you calculate the concentration or rate constant using the integrated laws?

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I have difficulty understanding how to solve the problem when it uses kinetics vs thermodynamics in the question? How do I solve the problem in both different cases?

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What is the difference between activation energy and free energy of activation and do the two relate to one another?

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What is the difference between using the volume and temperature change? If they are both calculating entropy change, does it result in the same value?

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How do you derive the Nernst equation?

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What is the relationship between work/ free energy with cell potential?

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Whenever I am solving problems, there are just so many equations that I have trouble figuring out which ones to use. If anyone has any tips and advice on how to indicate which equations to use during which times, that would be very helpful!

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How do I solve this problem? Ethene is a component of natural gas, and its combustion has been thoroughly studied. At a certain temperature and pres-sure, the unique rate of the combustion reaction C2H4(g) + 3 O2(g) --> 2 CO2(g) + 2 H2O(g) is 0.44 mol? L21?s21. (a) What is the rate at which oxygen r...

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How would I calculate a standard cell potential, given the half-reactions for the cell and their standard potentials?

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When do I know to use the Arrhenius equation?

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For all the 0,1,2 order reactions is it all plug and chug?

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What's the importance between galvanic and voltaic cells?

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How do I know when it’s zero, first, and second order?

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Can a non spontaneous process with a positive delta S become spontaneous if the temperature is increased (assuming that delta H and delta S are both independent of temperature)?

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What exactly does it mean when a process can be predicted solely in terms of the thermodynamic properties of the system? What are the thermodynamic properties?

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205405339 wrote:I was wondering by what time and day do we need to submit our take-home final by?

I think professor Lavelle said that it would be an open book 3 1/2 hours exam from 11:15 am -2:45 pm.

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Is the final exam going to be provided on professor Lavelle's website at exactly 11:15? I am currently informed that its something we would have to print out and fill out then scan, if so will it be provided a few minutes in advance to give students time to print it out and get settled in a good stu...

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I am getting a little anxious because I do not know general details about this final. What is the exact time limit? How are we going to be tested, is it all online and are we using zoom/video recording site while taking the test? How is the test formatted? I just feel like I do not know all the inf...

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Does anyone know how to scan from an at home wireless printer? Usually you'd just have to put your documents under the scanning part of the printer which is the part where you can open and close the printer and just press the scan function on it and it should either be sent to your desktop files or...

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Where would we submit the final? Do we just have to scan it and email it to our TA's? I just want to make sure I know what the exact process is so I can be prepared.

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How do you solve the reaction enthalpy of N2(g) + 3F2(g) ---> 2NF3(g)?

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WYacob_2C wrote:How were you able to figure out that Q is [anode]/[cathode]?

I think it is something that is just stated in the Nernst equation that Q is [anode]/[cathode].

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Ohh so is it only H+ that you add in acidic solutions to balance it out and use no H20? Because when I solved this problem I got 6H+ + Cl2O7(g) ---> 2ClO2- (aq) + H2O + 5e-...I got this problem partially wrong and I was wondering why I did.

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Okay that makes more sense, but how do you determine if I use that electron transfer or the other? I used 1 mol because I was looking at the Ag equation.

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Thank you! This was extremely helpful :)

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How does this solution get balanced: Cl2O7 (g) =H2O2(aq) ---> ClO2(aq) + O2(g)?

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The given half reactions are: Ag+ (aq) + e- ---> Ag(s) E*= 0.7996V Ni 2+ (aq) + 2e- ---> E*= -0.25V I solved for E*cell by using E*cell= E* right + E* left, which equaled to 1.0496V. Then I went to solve Gibbs free energy by using delta G*= -nFE*cell: -1 mol(96485 c/mol)(1.0497 V) and got -191270.65...

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I'm a little confused as to how Le Chatelier's Principle really applied.

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Calculate the equilibrium constant from the following thermodynamic data for this reaction at 30 degrees Celsius. CaCo3 (s) --> CaO (s) + CO2 (g), Delta S* = 181 J/mol and delta H* rxn= 221.5 kJ/ mol I started this problem off by plugging in the values into delta G*= delta H*- Tdelta S* and got 221....

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A concentration cell was constructed with two electrodes containing AgNO3 (ap) at 25 degrees Celsius. The cathode concentration is 3.0 M and the cell potential is 0.0644 V; a) calculate concentration of anode solution b) how will each of the following changes affect the cell potential? i) adding 100...

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When solving for concentrations with the ice table, in what situation can you assume x is too small and therefore can be excluded from the equation? EX: 0.2-x, in this situation would I just disregard x and just keep 0.2?

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When writing out the cell diagram when do you know when to use Pt and not to use Pt?

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In a combustion chamber, the total internal energy change produced from the burning of a fuel is -2573 kJ. The cooling system that surrounds the chamber absorbs 947 kJ as heat. How much work can be done by the fuel in the chamber? [CH 4B #7] I was a little confused with this problem because I though...

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Why are most exothermic reactions spontaneous?

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Katie Kyan 2K wrote:You can use the equation for the volume of a cylinder which is pi(r^2)h. Since you know the diameter of the pump, you can find its radius and the delta h would be 20. cm because this is how far the pump is depressed.

Thank you!

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I figured out how to solve it by using the volume formula for the cylindrical shape pump and found the change volume equation (delta V= pie*r^2*delta h) and got delta V= pie(1.5 cm)^2(-20.0 cm)= 141.37 cm^3 and used 0.001 L=1 cm^3 to convert and got -0.1437 L. Then plugged the delta V into work=-Pex...

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The inner diameter of the pump is 3.0 cm and the pump is depressed 20. cm with a pressure of 2.00 atm. This is a question where I would have to use the expansion work equation but in this situation for the change in volume how would i solve it? Question: 4A #3

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I know this isn't the right category and that this might be a 14A question but consider it being on one of the outlines, I was confused as to when you assume (with this equation Kw=[H30+] [OH-]) that the value is equal to [H30] or [OH]? Is it when something is completely deprotonated in water? For i...

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A reaction mixture that consisted of 0.400 mol H2 and 1.60 mol I2 was introduced into a flask of volume 3.00 L and heated. At equilibrium, 60.0% of the hydrogen gas had reacted. What is the equilibrium constant K for the reaction H2(g)1I2(g) ∆ 2 HI(g) at this temperature? When solving this do you ha...

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What is the difference in calculating the equilibrium concentration and the equilibrium molar concentration of a given molecule, or are these the same thing?

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How do you determine the change in partial pressure ("C")?

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When should you use K and Kc? It said whenever the calculations of an equilibrium constant from thermodynamic tables of data (standard Gibbs free energies of formation) it should use K and not Kc, why is this and what other instances would I have to keep this in mind?

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When should you put a "P" in front of the compound when writing out the equilibrium equation? Is it when it is a gas?

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When listing the products and reactants into the equilibrium constant equation does it matter which order they are listed in?

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I understand that the equilibrium constant is Kc or just K, but what does it mean when it is asking about the equilibrium constant of the products? For example it asks," if one starts with higher concentrations of reactants, the equilibrium concentrations of the products will be larger". I...

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I need a little clarification on the chart 5G.2 ("Equilibrium constants for various reactions") on page 402 in the text book. How do they get the T/K*,K, and Kc values...?

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What is the difference between saying "equilibrium is shifted to the right/left" versus when a reaction "lies to the right/left"?

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Why would the composition of the reaction mixture remain constant when it is at equilibrium?

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When you are naming, when should you use cobalt and cobaltate??

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When the bonding is on the C of CN and bonding is on the N of CN are they both cyanido because the text book called it both cyanido and isocyanido and i was wondering if they could be used interchangeably.

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when do I use the Ka and Kb equations?

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Malik Oda 1F wrote:
ShastaB4C wrote:Does anyone know approximately how many questions the final exam will be?

all I know is that it will be 3 hours, so one hour longer than the midterm

I think there are 8.

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I was going over the textbook and I was still confused on when I should use what equation when solving for the pH for certain things.

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If something were to have a negative pH what would that signify?

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How would you write the chemical equations of the two proton transfer equilibria that demonstrate the amphiprotic character of HCO32?

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also if an ion has a positive charge does that make it a base and if it has a negative charge would that make it acidic...

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When you see an N in the compound is it safe to assume that it is acidic?

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How are you able to tell if an ion is neutral, basic, or acidic? Is this where you are suppose to use the pH equations?

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Thanks this actually helped a lot, good luck :')

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What should be our main focus for this final? I know the final is cumulative but should we be studying more of post midterm concepts?

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Do we also need to go over the buffer solutions? I wasn't sure because I remember Professor Lavelle saying that it was a chem 14b concept...

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Do we need to know buffer solutions for the final? What materials should we cover from post midterm to prepare for the final?

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Buffer solutions usually contain a weak acid & the conj base. For example if there is HF and KF, this would be an example of a buffer solution because F- is the conj base for HF and KF has the F-.

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the base ends up being the conjugate acid and the acid ends up being the conjugate base. The conj. base is the one where H+ gets removed and the conj. acid is the one where the H+ is added to H20.

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When do you use the Ka and Kb equations...? What's the difference between those and the pH and pOH equations?

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when the equation involves a weak acid it is written with a double arrow because the reaction is reversible but when the equation involves a strong base it is just a single arrow. HCl+H2O --> H3O+ + Cl-, if it was a weak acid that arrow would have one facing the product and the other facing the reac...

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Thank you, and also when the equation is pH=-log [H+] it is the same as pH=-log[H3O+]?

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Will the equations like pH=-log [H+], Ka=x^2/Ha-x, and etc. be provided on the final?

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Do we just need to memorize the common strong&weak acids&bases for the final? Strong acids: HCl, HBr, HI, HNO3, H2SO4, HClO4 Weak acids: HF, NH4 (and its safe to assume its a weak base if its not on the common strong acids listed above?) *More oxygen=more acidic Strong bases: KOH, NaOH, BaOH...

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How do you determine what the conj. acid and bases are?

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What were the topics that were covered during these days? I ended up missing these lectures due to personal reason, if possible could someone send me the lecture notes please?

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When will test #2 be handed back?

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In the textbook it mentions that Hydrogen bonds are so strong (10% of covalent bond's strength) that it dominates all other types of intermolecular interactions (pg 192 of textbook).

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Do polar molecules have a higher boiling point than non-polar molecules?

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I think the text book was saying that the stationary molecules were referring to solids and the rotating molecules were referring to gases.

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In the text book it says that dipole-dipole has stationary & rotating polar molecules that are involved in this interaction. What does it mean by stationary & rotating? Does it have to do with the sigma and pi bonds?

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When would you use the Coulomb formula? (ch 3F.1)

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Which way do anions increase in polarizability? is it left and up the periodic table like cations or are they different?

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Thank you this helped a lot! I was also wondering whether we to draw the dipole arrow towards the positive or negative particle charge during the test and exams. I know that the text book specified the two different ones the original convention and the modern convention.

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I remember in discussion we were told that the temperatures for: H2O,H2S, H2Se, and H2Te went from high temp for H2O then drops down then starts from H2S and increases from then on to H2Te. I am a little confused on how this trend works.

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How do you determine which intermolecular force is involved in a molecule?

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I think hydrogen bonding is stronger than dipole-dipole, i'm not totally sure but I think hydrogen bonding should be the strongest of all the intermolecular forces. The strength of each intermolecular force from lowest to highest should be: induced-induced, dipole-induced, dipole-dipole, ion-dipole,...

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How are you able to determine which molecules have a higher or lower boiling/melting points?

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So do we technically need to do chapters 2D, 2E, and 2F, since the midterm was up until 2D right?

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Thanks that helped cleared things up, also is the electron arrangement the same thing as electron geometry?

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In the text book it said that if the shape was trigonal bipyramidal it should have 5 bonding pairs and no lone pairs but for example 2E.3 toolbox question in the text book mentions that SF4 is trigonal bipyramidal even though it had a lone pair because it has 5 regions of electron density. So does i...

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Where would we get the answers for test #1 because I'm using it to review for the midterm and I would like to know if I was solving these problems right.

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When something asks for its formula units what is it asking for? (HW Q: E.23)

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Is week 4's homework suppose to be questions from "the quantum world" or "chemical bonds"? I looked on the objectives and saw that the topics that Professor Lavelle went over in today's lecture (10/21/19) were on the quantum world. But I also know that he told us to do questions ...

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If it is mmol does that mean milli(10^-3) moles, also when converting moles to grams is it: moles x grams of the atom?

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If you were given the total molecular mass and given the mass percentage compositions of all the elements, how would you solve for the molecular formula using the total mass or would you just disregard it?

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Jasmine Vallarta 4E wrote:My TA told us that we would be provided with a periodic table with those values

Ok thank you!

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For test #1 will we be given a periodic table with the atomic masses or will we have to memorize those as well. Since these are used to calculate things on the test.

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When it asks to try estimate which element will have the greatest mass percentage without any calculations does that mean assume based on how many atoms of one element there are? Q:F3

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Thanks so much, I was just getting confused to whether it was the moles of something or the number of molecules of something.

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When something combusts, does it reacts with O2 and produce CO2 and H2O?

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When balancing equations, you're not able to just add an atom of something instead you're suppose to add more molecules of something right?

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LReedy_3I wrote:Yes, Avogadro's number is the number of atoms in one mole. For E7, I divided 2.1x10^9 atoms of carbon by 6.022x10^23 to determine the number of moles to be 3.5x10^-15 mol.

Thank you!

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Do you use the Avogadro's number when you have to convert the the number of atoms to moles? Q:E7

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During discussion, my TA said that Professor Lavelle is more lenient about sig figs because students use to ask a lot of questions about that during lecture and would take too much time away. But you should still be aware of the values given in the questions and use those sig figs. That doesn't mean...

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