CHEMISTRY COMMUNITY

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Will chem community points for 11 week be extra offered just help for the 10th week

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Will we still be following the curve grading scheme?

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How do we find the enthalpy for ionization?

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When would we get the results for the test?

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Aliya Jain 2B wrote:have you tried log(5.839) / log(2.5)?

I havent but is that something we have to do for experimental rate laws ?

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how would we find the experimental rate law for B if the conrations give me a value of 2.5 and the rates give me 5.83908046. I cant get second order which it is.

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Is the equation of the instantaneous rate of change (-d[A]/adt) the same as the differential rate law (K[R]^n)?
If it is then why is it that the differential rate law doesnt have a negative and the instantaneous does?

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What does that mean?

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Posting the question for reference: Screen Shot 2020-03-12 at 10.51.51 PM.png The cathode here is aluminum (E naught = -1.66V) and anode is magnesium (E naught = -2.36V). When subtracting, Ecell= E cathode - E anode, so -1.66V - (-2.36V) is +0.70V. The negatives cancel out. Perhaps you were confuse...

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if the equation for the E cell is cathode my anode, shouldnt the answer be -4.02?

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I didnt know where to ask this but on the third question of the professors study guide powerpoint where did he get the equation from? I dont recognize it

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How are you able to tell whether a a rxn is endo or exo just by the value of the fwd and rev rxns?

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What does the professor mean on his powerpoint for the final by "IF IT IS A SALT WITH A BASIC ANION, THEN pH > 7 AND CALCULATE [OH¯]
THEN USE pH + pOH = 14.00 TO CALCULATE pH"

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They're the steps we combine to get the overall reaction

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activation energy is in both types of reactions

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Are we only going to go up to Termolecuar?

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is A the initial concentration or given concentrations when plugging them into equations? or is it not even concentrations?

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So how exactly do we get the slope of the reaction

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Can someone explain what it means for EMF to be the max potential difference ?

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What does that mean

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What does the order of the reaction tell you ?

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What did the professor mean when he said the reaction of diamond to graphite was supported through kinetics more than thermo.

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What do we do when a a reaction doesn't have a solid?

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When do we use -RTlnK and -RTlnQ

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^I didnt see it on the solution manual on the class website, are you sure?

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makes it easier to distinguish between the redox reactions

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oxidation is losing electron, I believe oxidizing agent is the one that is reduced because it oxidizes the other molecule by taking the electrons

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oxidation and reduction reactions.
Reduction is when you gain an electron and rOxidation is when you lose one

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Leila_4G wrote:We are never given T so we can't solve the last step for w and therefore q.

could you explain to me the problem please? like values

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What is T

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6-8 pm and you can find the location on the class website

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Can someone help me solve problem 3B? I wasnt able to make it to the review session and the enthalpy of fusion is causing me problems

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Any tips or tricks on how to know which formula to use in question if they give you multiple givens, like Temp, Pressure or Volume?

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If the [] of a reactant is not given in then do we assume the [] is 1? I remember one of the TA's doing something like this in a review session but I cant exactly remember the question

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Just trying to reassure things before the midterm. When exactly can you tell that you would either need Ka or Kb?

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Why is it that we plug in the inverse of pressures as the volumes when solving the entropy of an ideal gas ?

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AArmellini_1I wrote:I don't have my homework on me right now but on thing I messed up on was using the wrong R, check your units and make sure everything cancels and you get the correct units. Different R's have different units

i figured it out , like a dumbo I didnt convert it to Kelvin

Thank you though!

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Ive read that we need to use 3/2 R and 5/2R with the formulas of Cp/v*ln(T2/T1) but I am not getting the right answers . is R not 8.3145? or do I need to divide the entire thing by 2?

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Justin Vayakone 1C wrote:My answer book shows 28J. Your statement regarding internal energy and work is correct.

Thank you

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Im getting a negative answer for heat released = heat absorbed, does anyone know why?
im doing 20*.39*(100-T)= 50.7*4.18(T-22)

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So I read in the book that the change in internal energy without the inclusion of heat is equal to the work. But in the answers, part C is 8j and not 28. does anyone know why?

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when do we know that X is too small to be making a difference for the denominator in the ICE box?

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Will the specific heat capacity be given on tests or will have to memorize some of them ? like water

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So out of the 3 Methods Professor Lavelle discussed, which will be most likely using more ? The first two seem to simple

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To find Ka/Kb from pH/pOH we would just need to do the inverse log of the the pH/pOH correct?

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Can someone please clarify an example professor Lavelle gave once about 1*10^-11 M HCl not creating that much concentration of H3O+ and then stating that H2O has 1*10^-7 [] of H3O+? I didn't write down everything and now its kind of confusing me.

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Alicia Lin 2F wrote:for every one mole of Ba(OH)2, there is 2 moles of OH- produced. Remember to take the concentration of Ba(OH)2 and multiply by 2 before taking the -log.

Thanks

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I found the pOH of the concentration of Ba(OH)2 and it was 2.036212173 but in hte answers it says 1.74. has anyone else gotten this ?

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Its called partial pressure because you are only calculating the pressure of that one gas in the mixture of gases so you're only getting one piece reaction. Thats why there is a partial pressure and a total pressure.

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I think you use PV=nRT when you're trying to switch between concentration and pressure of when trying to calculate the partial pressures.

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P is for partial pressure, usually used when the reaction only has gases and no aqueous solutions

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briannam_1F wrote:When calculating for Q do we omit solids and pure liquids as well?

Yes you would leave them out because Q is pretty much K, with the difference being that Q is at any time during the reaction but you would calculate it the same way as K

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The question asks to determine if the statement is true or false and explain why. In part c it states "If one starts with higher pressure of reactant, the equilibrium constant will be larger." I thought this was true because if there is higher pressure of reactant it will shift toward the...

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Why is it that when we add reactions together we multiply the K's ?

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If Kc and Kp are suppose to be the same, then why does the chart on 5G.2 have different values for some K and Kc?

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nicolely3B wrote:The last three audio-visual focus topics on Prof Lavelle's website all have a bunch of questions with wavelengths, but you have to go through the simpler, conceptual questions first. Other than that, I think Dino Nuggets (towards the end) has the best

thanks

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How do we go about finding the shape for ligands ? how was c on minimarshamllow an octahedron ?

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Final, does anyone know if the test will be evenly distributed or if it will focus more on items after the midterm

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Minimarshamllow, how do you know when a compound will make an acid or base?

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Does anyone know any good wavelength questions that would be good to practice ?

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could someone explain #34 on marshmallow to me? Is the solution basic or acidic and why? How do we know whether it'll be acidic or basic

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On question number 21 of the Marshmallow review. Why does iron have a +2 charge if two of the nitrogens on the porphyrin ligand have a +1 charge? The two nitrogens actually have a -1 charge, not +1. How is the charge for the nitrogens -1? I believe its -1 because of the 4 Bonds (2 single, 1 double)...

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For mini marshmallow 2c why does Potassium dicyanobis(ethylenediamine)cuprate (I) have a coordination number of 6? doesnnt it only have 4 atoms around it? or does the chelating ligand add more.

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For naming the new compounds we have been learning, will this be something crucial in knowing or is it just useful knowledge in knowing how to identify compounds and such.

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AnvitaaAnandkumar_1B wrote:I think the TAs said you would be able to see it at the end of the quarter.

but there's no way of viewing how many i have or haven't done correct? Would it even be such a big impact on my grade ?

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Does anyone know if we will get some sort of study tools again?

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205150314 wrote:So how can we try to figure out the grade we might get? or si there no way of finding that out right now

If the midterm average was like a 75 then what would be considered an A for that test if the professor based the grading scheme on the average?

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So how can we try to figure out the grade we might get? or si there no way of finding that out right now

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Does the coordination number describe the ligand or the central atom of the ligands?

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is there any way to check the online discussion points ?

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Benjamin Feng 4B wrote:AsF3 also has a lone electron pair, which counts as an electron domain. This makes for 4 total domains and therefore sp3 hybridization.

oh okay thank you, I was thinking that only bonds counted as the electron density areas

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How does AsF3 use a sp3 hybrid orbital if it only has 3 areas or electron density ?

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Sidharth D wrote:The test will probably focus on elements up until the 3p block.

Do you know if we also need to know about the orientation of the orbitals ?

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Sidharth D wrote:The test will probably focus on elements up until the 3p block.

Thank you

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Will the the test possibly have hybridization for elements with long electron configurations ? or is it okay to focus on the smaller elements ?

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why do we need to give bonds a secondary name? what do the names mean?

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Kimberly Bauer 4E wrote:How many questions are on test 2 and what topics will be covered aside from polarity, IMFS, VSEPR, and Sigma and Pi bonds? Is it mostly conceptual compared to Test1 and the midterm?

sigma and pi bonds?

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Will test 2 be the same length as test 1?

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Does anyone have any good tips on how to remember bond angles?

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Does anyone know what to do for 13a?

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Could someone please explain 8b please? I used the photoelectric effect equation relating kinetic energy, energy of the photon, and the work function, but for some reason I'm not getting the correct answer. i think they used the wrong mass of an electron because when i went to the review session th...

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Could someone please explain 8b please? I used the photoelectric effect equation relating kinetic energy, energy of the photon, and the work function, but for some reason I'm not getting the correct answer. i think they used the wrong mass of an electron because when i went to the review session th...

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Could someone help me on 8B?

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8. B) A newly designed laser pointer with a certain frequency is pointed at a sodium at a sodium metal surface. An electron is ejected from the metal surface with wavelength 1.10nm. What is the frequency of the light from the laser pointer? The work function of sodium is 150.6 kJmol^1. I understand...

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For 6b., I am confused about why GarBreadium has the longer deBroglie wavelength. Shouldn't it be He because it weighs more? GarBreadium weighs less so it'll make the denominator smaller compared to the denominator of He so the outcome (length) will be larger than if you were to divide by a larger ...

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For Dino Nuggets 6a, what equation do we need to use ? ive been trying to use different one (because theres a lot for E) and that molar mass is messing me up.

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Can someone please explain how to solve question 2 from Dino Nuggets? Conceptually, I understand how to solve this type of problem but my numbers keep coming out different so I must be doing something wrong. Thank you! I'm having the same problem, if you found the answer could you please let me know

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Micah3J wrote:If I am unable to make the review session tomorrow night but still work out the problems on my own, will the answers be posted on here so I can check my work?

Yea it says it right there that the answers will be posted after the review session

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In the case of copper, a full d subshell is more stable than only being partially filled. This means that the electron configuration of Cu is [Ar] 3d10 4s1. Since this question asks about Cu+, there is one less electron, so it is taken out from the s subshell to maintain the full d subshell. So the...

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The question asks from which orbital will an electron need to be removed from to form a +1 ion but for b, doesnt Cl form an anion?

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Why do the ions have missing electrons from the orbitals that come before like for Cu+ why is he electron taken out of 4s2 and why were both taken out ?

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Remember that valence electrons are the amount of electrons in the outermost shell, or the highest n-value. For an atom configuration with say, [Ar] 3d10 4s2 4p3, the outermost shell is 4, so the electrons with the n=4 are the valence electrons. So that particular atom has 5 valence electrons. For ...

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Yes, the roman numerals represent the charge for the transition metals

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People have gotten a text saying classes have been cancelled , so we still have to go or not ?

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So do we place them in order by that image or by n?

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For ground state does every orbital need to have at least one electron in it before pairing , otherwise its excited?

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My TA told me to do it by n, so keep all the same n together

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yes they are pretty much the same thing with different meanings. Right and up increases.

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Resonance are just variations of the Lewis dot diagram. I think it typically just on how you can change the bonds.

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For this problem, I got delta p as greater than or equal to 1.51*10^-25. However, when I try to find delta v, the solution manual states to multiply by 1/2, so it looks like this: .5((1.5*10^-34)/(9.1*10^-31)(350*10^-12))= 1.65*10^5 m/s. Again, why would you multiply that by .5? Isn't the original ...

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