CHEMISTRY COMMUNITY

Hana Sigsbee 3B

I would assume so.

Hana Sigsbee 3B

"The presence of a catalyst provides a reaction pathway in which the activation energy of a reaction is reduced by 31.00 kJ⋅mol−1 . Uncatalyzed: A⟶B Ea=115.00 kJ⋅mol−1 Catalyzed: A⟶B Ea=84.00 kJ⋅mol−1 Determine the factor by which the catalyzed reaction is faster than the uncatalyzed reaction a...

Hana Sigsbee 3B

"A certain reaction has an enthalpy of ΔH=34 kJ and an activation energy of Ea=71 kJ. What is the activation energy of the reverse reaction?" Hi, the hints for this problem say to draw out an energy diagram but I still am not getting it. Would someone please be able to lay out the steps to...

Hana Sigsbee 3B

"The mechanism proposed for the oxidation of iodide ion, I−, by the hypochlorite ion, ClO−, in aqueous solution is shown. ClO−(aq)+H2O(l)⇌HClO(aq)+OH−(aq)fast in both directions I−(aq)+HClO(aq)→HIO(aq)+Cl−(aq) slow HIO(aq)+OH−(aq)→IO−(aq)+H2O(l) fast Complete the rate law for the formation of I...

Hana Sigsbee 3B

"Dinitrogen pentoxide, N2O5, decomposes by first‑order kinetics with a rate constant of 3.7×10−5 s−1 at 298 K. What is the half‑life, in hours, of N2O5 at 298 K? If [N2O5]0=0.0679 mol⋅L−1, what will be the concentration of N2O5 after 2.7 h? [N2O5]: How much time, in minutes, will elapse before ...

Hana Sigsbee 3B

I try and find the hardest most complicated problems in the book to practice before the final.

Hana Sigsbee 3B

I am a freshman and I am very looking forward to getting to know what life is even like at UCLA because I of course have no clue what to expect.

Hana Sigsbee 3B

The distribution of questions last quarter was based on the size of the unit.

Hana Sigsbee 3B

I find handwritten notes are best for me and I believe there is research showing that writing things out by hand helps to commit it to memory.

Hana Sigsbee 3B

I try to find time to relax and destress and try to get in a mindset where I am not even thinking about school because if you're trying to relax and you're just thinking about all the work you have to do the whole time it's not really relaxing.

Hana Sigsbee 3B

What would the potential of a standard hydrogen electrode (S.H.E.) be under the given conditions?

[H+]=0.46 MPH2=4.9 atm T=298 K

Hi does anyone know what section of the textbook I could reference to try and solve this because honestly I have no clue where to start with this one.

Hana Sigsbee 3B

"One of the most recognizable corrosion reactions is the rusting of iron. Rust is caused by iron reacting with oxygen gas in the presence of water to create an oxide layer. Iron can form several different oxides, each having its own unique color. Red rust is caused by the formation of iron(III)...

Hana Sigsbee 3B

"Calculate the cell potential for the reaction as written at 25.00 °C , given that [Cr2+]=0.791 M and [Fe2+]=0.0140 M . Use the standard reduction potentials in this table. Cr(s)+Fe2+(aq)↽−−⇀ Cr2+(aq)+Fe(s)" I think the part I may be doing wrong on this is calculating either Q or n but I a...

Hana Sigsbee 3B

"Calculate the standard free-energy change for the reaction at 25 ∘C. Refer to the list of standard reduction potentials. 2Au3+(aq)+3Ni(s)↽−−⇀2Au(s)+3Ni2+(aq)" So far every time I have tried this problem I have gotten wildly different answers because I gave tried it multiple ways but they ...

Hana Sigsbee 3B

"A galvanic (voltaic) cell consists of an electrode composed of iron in a 1.0 M iron(II) ion solution and another electrode composed of copper in a 1.0 M copper(I) ion solution, connected by a salt bridge. Calculate the standard potential for this cell at 25 °C. Refer to the list of standard re...

Hana Sigsbee 3B

"Identify the oxidizing and reducing agents in the skeletal (unbalanced) reaction. Then, balance the reaction, including the phase (solid, liquid, etc.) of each species. The reaction takes place in basic aqueous solution. Cl2O7(g)+H2O2(aq)⟶ClO−2(aq)+O2(g) Identify the oxidizing and reducing age...

Hana Sigsbee 3B

"For a particular redox reaction, NO is oxidized to NO−3 and Cu2+ is reduced to Cu+ . Complete and balance the equation for this reaction in basic solution. The phases are optional." Hi, I am having a hard time with this question for some reason, could someone give me some guidance on how ...

Hana Sigsbee 3B

Hi, so I know that the minimum to pass with a C- is 50% but I was wondering, does anyone know what the grade scale is after that?

Hana Sigsbee 3B

All the problems that relate to each topic are listed under the outlines on the syllabus but those obviously will not all be on the exams.

Hana Sigsbee 3B

I personally did not do great either and I reviewed sapling, textbook, outlines, lecture notes, and went to review sessions but I feel I would have done better if I was more engaged with the studying and not just doing it like I am going through the motions.

Hana Sigsbee 3B

I try to remember it as oxidize is losing and reducing is gaining, so the oxidizing part gains the electron but the reducing part loses and electron.

Hana Sigsbee 3B

No, I don't think so, I think the coefficient balances the equation but is not part of the calculation.

Hana Sigsbee 3B

haha that's so funny, that's exactly what I did. The new episode of WandaVision was crazy.

Hana Sigsbee 3B

Dr.Lavelle emailed saying...
Midterm 2 will not cover any electrochemistry.

Midterm 2 covers:

Outline 3: Thermochemistry (but not the MT1 topics*)

Outline 4: Thermodynamics

*The MT1 topics (different ways of calculating reaction enthalpy) are not covered in MT2.

Hana Sigsbee 3B

Dr.Lavelle emailed saying that "Midterm 2 will not cover any electrochemistry.

Midterm 2 covers:

Outline 3: Thermochemistry (but not the MT1 topics*)

Outline 4: Thermodynamics"

Hana Sigsbee 3B

Hi, so I am struggling in this class. I do all the problems outlined on the syllabus, I watch and rewatch lectures, I take notes on and read the entirety of the textbook sections but I got a pretty bad score on my midterm. Does anyone have any suggestions on what else I could be doing for better ret...

Hana Sigsbee 3B

The molar heat capacity for carbon monoxide at constant volume is CV, m=20.17 J/(K·mol) . An 8.00 -L fixed-volume flask contains CO(g) at a pressure of 2.00 kPa and a temperature of 25.0 °C. Assuming that carbon monoxide acts as an ideal gas and that its heat capacity is constant over the given temp...

Hana Sigsbee 3B

This is so fun, I noticed the application of chemistry a lot in baking like baking is such an exact science because it's basically just chemical reactions coming together to make the end product, and if you get one of those reactions just a little off the whole thing is wrong.

Hana Sigsbee 3B

The grading was input for week 5 as well even though week 5 was not done, Dr Lavelle sent an email talking about it. I got scared too.

Hana Sigsbee 3B

I find a quiet room and just do my best to toon everything out, I know its hard sometimes though.

Hana Sigsbee 3B

do we know when the rest of the sapling assignments for the quarter will be posted? I know it's a little soon since we haven't started the next topics I just like having it all written out in my planner.

Hana Sigsbee 3B

is midterm 2 cumulative or does it just cover everything we will have covered since midterm 1?

Hana Sigsbee 3B

Hi, do we attend any office hours to review our exams?

Hana Sigsbee 3B

No, my TA has said we do not need to memorize these and that if we ever need to use them they will be provided.

Hana Sigsbee 3B

Hi, I was wondering when other people are planning on taking 14Bl and 14CL because I am not sure what the best planning would be to work them into my schedule, when do most people take those classes?

Hana Sigsbee 3B

A closed system prevents volume change because there is no exchange of matter with the system's surroundings so nothing can leave the system so its volume stays consistent.

Hana Sigsbee 3B

Knowing the type of system is important so you are aware if there is any exchange in matter or energy with the system's surroundings because if there is an exchange that would affect the makeup of the system.

Hana Sigsbee 3B

since an isolated system does not exchange energy or matter with its surroundings an example Dr.Lavelle gave during the lecture was a really well-insulated thermos.

Hana Sigsbee 3B

Midterm 1 covers Chemical Equilibria, Acid and Base Equilibria, and only these Week 3 topics (4D.3; 4D.4; 4D.5; 4E.3). Last quarter it was structured so whichever topic we spent the most time on would have a larger portion of the test so it was proportional to the class.

Hana Sigsbee 3B

Dr.Lavelle emailed saying that "midterm 1 covers Chemical Equilibria, Acid and Base Equilibria, and only these Week 3 topics (4D.3; 4D.4; 4D.5; 4E.3)."

Hana Sigsbee 3B

yes, we print out the equations sheet and periodic table from Dr. Lavelle's website to use on the tests.

Hana Sigsbee 3B

Yes, endothermic reactions will always have a positive delta H because the change is positive and exothermic reactions will always have a negative delta H because the change is negative.

Hana Sigsbee 3B

Has Dr.Lavelle told us if we will be using a zoom for proctoring of the midterms?

Hana Sigsbee 3B

An inert gas changes the total pressure of the entire system, it has no effect on the partial pressures of the individual components of the system.

Hana Sigsbee 3B

My little "dumbed down" version of it that I remember it with is essential that if the system is acted on it will compensate for that but doing more of the opposite action to keep the original K value.

Hana Sigsbee 3B

yes, personally I know ICE tables are used when doing these calculations but I like to use them on most problems just to keep everything organized and make sure I'm not missing anything

Hana Sigsbee 3B

Hi, I would use mol/L just to have consistency and prevent any little mistakes later on.

Hana Sigsbee 3B

if both x values are positive one will likely be too big to be an option, like it will be larger than the concentration of one of the reactants or products so in that case, you would use the smaller x value.

Hana Sigsbee 3B

Hi, I know last quarter for 14B we did our midterms at our discussion section times, does anyone know if we will be continuing to do so this quarter?

Hana Sigsbee 3B

I believe Dr.Lavelle has said we do not use non-ideal gases in the course but possibly in some upper-division chemistry courses we might.

Hana Sigsbee 3B

we assume all gases are ideal gases even though very few are but by assuming so we are able to use PV=nRT

Hana Sigsbee 3B

we find Q instead of K when the reaction is not at equilibrium. Q can be used to compare to a given K to find if the reaction favors products or reactants.

Hana Sigsbee 3B

when a reaction is reversed K is inversed as 1/K

Hana Sigsbee 3B

The c in Kc refers to concentration and the p in Kp refers to pressure so for equations referring to gases you would use Kp as it refers to the pressure of the gas.

Hana Sigsbee 3B

what I found to be most useful was ensuring I did all the assigned bookwork and then before exams making my own study guide out of questions from each topic that was assigned and doing even more practice.

Hana Sigsbee 3B

I think you would be able to as long as you're in the lockdown browser otherwise I do not think you can because you would be able to access other materials on it.

Hana Sigsbee 3B

Hi, yes if you want to arrange solutions on their pH, the strong acids will have the lowest pH and the strong bases will have the highest pH so it makes sense to identify these to put them in order. Then of course weak bases will have a lower pH than the strong bases but still higher than the acids ...

Hana Sigsbee 3B

Hi everyone, I know Dr. Lavelles has provided us with great review resources this week and throughout the whole quarter but if anyone is still feeling those prefinal nerves like I am I just wanted to give a heads up, The Organic Chemistry Tutor on youtube has some really great, short, concise, video...

Hana Sigsbee 3B

Some of the problems will be from the textbook but not all of them.

Hana Sigsbee 3B

I would suggest maybe a week before class starts up again start reviewing the content of 14A similarly to how you are studying for the final.

Hana Sigsbee 3B

I remember that we obviously need to charge to be equal to the charge given in the problem so I add all the known charges and then I know the oxidation number of the unknown will make it reach the correct charge from there. For example, if the total charge is known to be +1 and with the given charge...

Hana Sigsbee 3B

can someone explain how they got the pH for d, e, and f for this problem, please? Thank you.

Hana Sigsbee 3B

Personally, I am taking 14B and 14BL later on and that is what I have seen other people are doing too but I would have taken them together if I would have had enough units available to do so.

Hana Sigsbee 3B

the coordination number is equal to the number of bonds attached to the central atom

Hana Sigsbee 3B

naming is based on the actual name, not the prefix.

Hana Sigsbee 3B

A chelate is a compound with a ligand that forms a ring of atoms that includes the central metal atom. They include the bidentate, tridentate, and hexadentate ligands which means they are donating 2, 3, or 6 lone pairs. I hope this helped.

Hana Sigsbee 3B

I know in the syllabus it gives us a breakdown of how many point each assignment and each test is worth and says that we have to have a 50% to pass with a -C. Do we know anything else about the grading for this class, like what the break down is for the rest of the letter grades, like what percent w...

Hana Sigsbee 3B

To determine if the overall molecule is polar or non-polar it's non-polar if the bonds are non-polar but if the bonds are polar we have to know the molecule's shape and bond angles to see if the polar bonds cancel out and if they do then the molecule if non-polar, correct?

Hana Sigsbee 3B

to determine if the bonds are polar or non-polar we just have to know if the two elements have the same electronegativity or not correct? And if they do have the same it's non-polar and if they're different it's polar?

Hana Sigsbee 3B

I noticed that under the grades tab on sapling there are three extra credit sections for the Math Review, Practice Drawing Molecules, and Chemical Equations Training. Are these assignments actually worth extra credit towards our grade or were they just input as that because they weren't actually ass...

Hana Sigsbee 3B

will all the molecules we have to determine the shape of be one of the shapes given to us in our notes, or are there any other shapes we should know about? Also just to double-check the shapes we have been given are: linear, angular, trigonal planar, trigonal pyramidal, t-shaped, tetrahedral, see-sa...

Hana Sigsbee 3B

Will we still have a lecture on Friday the week of Thanksgiving? I know we're supposed to have that day off but I know on Veterans day we had a lecture.

Hana Sigsbee 3B

2E.5 (a) What is the shape of a ion? (b) What is the expected OClO bond angle?

Hana Sigsbee 3B

I try to not stay up too late the night before studying, and if anything do maybe a quick review of the topics you feel you need it in the most. The night before I like to meditate or do yoga before bed and make sure I get a good night's sleep. I have my discussion early in the morning but I try to ...

Hana Sigsbee 3B

do we know yet if the final will be like the midterm and just cover the most recent topics, or will it be cumulative?

Hana Sigsbee 3B

I understand how to determine the shape based on the 3d models but I'm not 100% on how to do so without, could anyone please give me a basic overview on how to do so. I know this is a bit of a silly question, but thank you.

Hana Sigsbee 3B

Hi, I am currently trying to plan out my classes for next quarter. I was not sure if it is required to take 14B and 14BL at the same time, because the final for 14BL conflicts with the final for my math class so I would rather not risk that overlap. Does anyone have any recommendations for what I sh...

Hana Sigsbee 3B

I know in the textbook we are given the original as well as the modern notation for showing an electric dipole. The textbook says they use the modern notation, is that what we should use as well?

Hana Sigsbee 3B

"2C.15 Two contributions to the resonance structure are shown below for each species. Determine the formal charge on each atom and then, if possible, identify the Lewis structure of lower energy for each species." How would we tell which lewis structure has lower energy based on the lewis ...

Hana Sigsbee 3B

"2B.3 Draw the Lewis structure of BrF3" for this problem why does the Br in the lewis structure have 10 electrons?

Hana Sigsbee 3B

"2A.15 Write the most likely charge for the ions formed by each of the following elements: (d) Ga" why will the charge of Ga be +3?

Hana Sigsbee 3B

Hi, I am struggling a bit with this section so far. Does anyone know of any good youtube channels or any other resources that I could use to supplement the resources given to us through this class?

Hana Sigsbee 3B

L is the number of unpaired electrons and you should be able to find this by just counting the number of unpaired dots in the Lewis Structure model.

Hana Sigsbee 3B

are there any exceptions to the octet rule we need to know off the top of our heads or will we be able to tell when we do the configurations if they are an exception all the time?

Hana Sigsbee 3B

Hi, I believe a good thing to keep in mind for this is that when the formal charge is zero that is when it is most stable so that is the ideal state.

Hana Sigsbee 3B

You use an electron microscope in which the matter wave associated with the electron beam has a wavelength of 0.0237 nm. What is the kinetic energy of an electron in the beam, expressed in electron volts?

Hana Sigsbee 3B

so on this problem, I got the energy for the photon easily but for some reason, the energy for the electron is giving me trouble. Could someone please walk me through that part a little more thoroughly? I've done it a couple of times now and I'm still not sure what I'm doing wrong.

Hana Sigsbee 3B

The electron affinity of thulium has been measured by a technique known as laser photodetachment electron spectroscopy. In this technique, a gaseous beam of the anions of an element is bombarded with photons from a laser. Electrons from the anion are then ejected and their energies are detected. The...

Hana Sigsbee 3B

The E.coli bacterium is about 2.0 μm long. Suppose you want to study it using photons of that wavelength or electrons having that de Broglie wavelength.
how would I start this problem to find the energy of the photon as well as the energy of the electron?

Hana Sigsbee 3B

"As you may well know, placing metal objects inside a microwave oven can generate sparks. Two of your friends are arguing over the cause of the sparking, with one stating that the microwaves "herd" electrons into "pointy" areas of the metal object, from which the electrons j...

Hana Sigsbee 3B

"The electron in a hydrogen atom is excited to the n=6 shell and emits electromagnetic radiation when returning to lower energy levels. Determine the number of spectral lines that could appear when this electron returns to the lower energy levels, as well as the wavelength range in nanometers.&...

Hana Sigsbee 3B

For the midterm, should we be using the printable lists of constants and equations off of Dr. Lavelle's website or should we use the one he has linked to buy through Amazon.

Hana Sigsbee 3B

Dr. Lavelle's email stated this midterm only covers up to last Wednesday's lecture, homework 1D, and up to sapling homework problem 19. He also said the "Review of Chemical and Physical Principles" as well as up to the tenth bullet point of the "Quantum World" outline is the cont...

Hana Sigsbee 3B

I believe we just have to have an understanding of how the equations were derived but I do not believe we will be required to actually show how they were derived.

Hana Sigsbee 3B

Hi, I have noticed that in lectures and practice problems the constants are generally rounded but he has said to keep all values and not round until the end number to ensure you get the correct value and number of sig figs so I would not round at first just to be safe.

Hana Sigsbee 3B

are there any specific conversion factors we are expected to know for the midterm that are not basic common knowledge ones?

Hana Sigsbee 3B

For 1E.7 in the textbook, how would we "Determine whether each of the following electron configurations represents the ground state or an excited state of the atom given." based on the model that was given?

Hana Sigsbee 3B

when predicting an electron configuration, how would we know if a certain element will follow the pattern or not?

Hana Sigsbee 3B

1B.15 The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 × 10 3 km ⋅ s − 1 . (a) What is the wavelength of the ejected electron? (b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50 × 10 16 Hz . How much ener...

Hana Sigsbee 3B

"1B.9 A lamp rated at 32 W ( 1 W = 1 J ⋅ s − 1 ) emits violet light of wavelength 420 nm. How many photons of violet light can the lamp generate in 2.0 s? How many moles of photons are emitted in that time interval?" would anyone be able to give me a step by step explanation on how to do t...

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