CHEMISTRY COMMUNITY

RichBollini4G

chrisleung-2J wrote:I believe that the take-home final is supposed to be taken during the same time as the in-class one, which is this Sunday from 11:30AM - 2:30PM.

Thank you!

RichBollini4G

Abhi Vempati 2H wrote:It seems the same as 14A, and I think the only thing that might change is how he adjusts the grades based on the class's performance this quarter.

So do we know how he is curving the class?

RichBollini4G

Last quarter when I took chem 14A it was a lot easier to keep track of, but since I have above 50 posts already it is difficult to count how many I have for each week! Is there a way to differentiate between quarters or will it be if I get 100 overall by the end? I believe if you get 100 by the end...

RichBollini4G

Given the information we just received about the virus, are we still having an in-person final?

RichBollini4G

Does anyone know if there will be any review sessions or anything like that specifically for test 2?

RichBollini4G

Fatemah Yacoub 1F wrote:Yes, I believe the test covers the second page of the thermodynamics outline and all of the electrochemistry outline

Thank you.

RichBollini4G

Test 2 covers the 2nd page of Outline 4 and all of Outline 5 Some of the major topics are: -Gibbs Free Energy -Van't Hoff Equation -Galvanic/Voltaic Cells -Redox Reactions -Cell Potential -Nernst Equation There are more topics so definitely check out the outlines for the more specific information y...

RichBollini4G

Christine Honda 2I wrote:As Dr. Lavelle mentioned at the end of the lecture today, the test will cover the second page of the Thermodynamics outline and all of the Electrochemistry Outline. But the test will NOT include Chemical Kinetics.

Does that mean chapters 5 and 6 respectively?

RichBollini4G

Mandeep Garcha 2H wrote:Anything in the second page in outline 4 and all of outline 5 can be on the test.

Do you know what sections in the book they are?

RichBollini4G

KarineKim2L wrote:Test 2 covers the part of thermodynamics that wasn't on the midterm and all of the Electrochemistry outline.

Do you know exactly what sections those are?

RichBollini4G

sbeall_1C wrote:Test 9 is covering the last page of the thermodynamics syllabus and the electrochemistry syllabus.

This refers to HW problems:
5G: 13, 15, 17, 19, 21
5J: 11,13, 15
5.55, 5.61

And all the HW probs outlined on the electrochemistry syllabus (Focus 6K-6O.1)

Thank You very much.

RichBollini4G

Megan Kirschner wrote:I think it's likely it will focus on the thermodynamics stuff that wasn't on the midterm, beginning with the content taught during week 6. But obviously there can be overlap since it's all connected.

Thank you!

RichBollini4G

Myka G 1l wrote:Both tests are worth 50 points.

thank you!

RichBollini4G

Christineg1G wrote:Official study guides haven't been made for this class, but I would recommend making your own with the notes from class as well as going to multiple peer learning sessions since they give worksheets/additional notes.

Thank you!

RichBollini4G

To add on, does anyone know exactly what sections we are required to know for the second test?

RichBollini4G

As more atoms are in a molecule, the number of microstates (possible arrangements) increase and thus there are overall more ways to distribute the motional energy of the molecules within the gas sample. In lecture, Dr. Lavelle uses the number of microstates as the primary indication of change in en...

RichBollini4G

you would use dS= n* C * ln (T2/T1) when there is more or less than 1 mole of the substance. you would use dS= C * ln (T2/T1) if they dont specify of it it's 1 mole. you use this equations for thermal disorder, where the temperature is changing. be sure to note that C can be Cv or Cp depending on i...

RichBollini4G

Megan Cao 1I wrote:S is just entropy itself
delta S is the change in entropy
delta S total is the total change in entropy within a universe ( S_sys + S_surr)
delta S surroundings is the change in entropy within the surroundings

Hope this helps in some way!

thank you this was very helpful

RichBollini4G

Mukil_Pari_2I wrote:Residual entropy is the difference in entropy between a non-equilibrium state and crystal state of a substance close to absolute zero.

thank you

RichBollini4G

Jarrett Peyrefitte 2K wrote:How is delta S related to delta H for a change at a constant temperature and pressure? What is their relationship?

The two are related through this equation: ∆S=∆H/T (from ∆G = ∆H - T∆S, when ∆G = 0)

RichBollini4G

Standard entropy means the entropy of a certain substance under standard conditions. They would usually be given in a table format (like we saw on the midterm, we were given the standard molar entropy of different molecules) Here is a brief article explaining it: https://chem.libretexts.org/Bookshe...

RichBollini4G

Eunice Nguyen 4I wrote:There is no transfer of heat, so q will equal 0.

thank you

RichBollini4G

Larger molecules have more particles and therefore have a greater positional entropy value. For example an element with more particles (electrons, protons, and neutrons) (such as Pb vs C) will have a larger degeneracy number, where W=#microstates^(#particles). Then use the equation S=kb(lnW) to sol...

RichBollini4G

Mariah wrote:When is test 2?

On the test and exam schedule it says they are starting the week of march 3rd.

RichBollini4G

for anyone that's been, have you found them helpful/how is the pace of the step-up sessions I've only been to Lyndon's and Melody's sessions, but I also agree that they are very useful and helpful! They both make worksheets for their sessions, but Lyndon's is a workshop, so he gives you time to wor...

RichBollini4G

Meredithe DeGuzman4G wrote:It's because the integral calculates the area under the curve. In the pressure v volume graph, calculating the area under the curve will give you the amount of work done to the surroundings.

Thank you

RichBollini4G

Bilal Pandit 1J wrote:w is given in joules.

thank you

RichBollini4G

Hannah Romeo 1J wrote:How do we know when to use the different work equations? I believe that both occur at constant pressure; however, when do we know which equation to use?

I would say look at what values the problem gives you, along with looking at all the units to make sure everything ends up cancelling.

RichBollini4G

connie 2C wrote:in the second equation, would we ever have to use the integral or would we just be using the equation -nRT(V2/V1)?

I believe it depends on the question.

RichBollini4G

The proportion between W2/W1 and V2/V1 will always be equal, although the value of W2 and V2 will be different. How can the proportions be the same but the values be different? Can someone please elaborate or give an example so I can further understand? (: W2 does not necessarily equal V2 and W1 do...

RichBollini4G

VLi_2B wrote:Kelvin = Celsius + 273.15

Celsius = Kelvin - 273.15

Because the difference between Celsius and Kelvin is addition/subtration; the difference/sum will always be the same.

Thank you

RichBollini4G

I guess we would actually only have to integrate if we were given some sort of equation for pressure that is a function of volume, without the number of moles or temperature for the problem. Otherwise, if we know the final and initial volume, the number of moles, and temperature at which the reacti...

RichBollini4G

Right now, the only instance where we would have to use calculus is calculating the work done by reversible expansion, which is given by w = -(integral) Pdv. However, in many cases this can simplify to w= -nRTln(V2/V1), which is a simplified version of the integral that we can use if are given the ...

RichBollini4G

105335337 wrote:You just need to know that if pressure is constant, the integral results in P (delta)T & if pressure is not it results in nrtln(v2/v1).

Thank you

RichBollini4G

AKhanna_3H wrote:Internal energy is represented by delta U. Q represents the heat entering or exiting the system.

Thank you

RichBollini4G

Jeremy_Guiman2E wrote:Homework 3 should probably be from the Acids and Bases Equilibria section given that we finished covering it last week (and we already completed the Chemical Equilibrium section as well).

thank you

RichBollini4G

Shail Avasthi 3C wrote:The value of R you use depends on the units given to you in the problem and the units which your answer needs to be in. The units of R will cancel out with all of the given terms to give you your final answer's units.

Thank you

RichBollini4G

Leslie Almaraz 4G wrote:How do you know which variation of the R constant to use?

I would say look at the specific units of the problem.

RichBollini4G

Andrew Pfeiffer 2E wrote:Roughly 3.34 x 10^-9 m

thank you very much

RichBollini4G

Chloe Alviz 1E wrote:We don't really need to know this concept; as long as you know what values you plug into for the formula you should be fine.

thank you

RichBollini4G

BNgo_2L wrote:Liquids and Solids don't have/have minimal changes in pressures nor concentrations, so they are typically not involved in computing the equilibrium constant.

very helpful, thank you

RichBollini4G

Wendy Perez 1E wrote:Strong acids do have a Ka value. They have large Ka values because the higher the Ka, the more the acid dissociates. They have low pKa values.

very helpful, thank you

RichBollini4G

In lecture, the professor went over a question involving the reaction CH_{3}COOH(aq) + H_{2}O(l)\leftrightharpoons CHCOO^{-}(aq) + H_{3}O^{+}(aq) and used the ICE table. Why is the intial value of H 2 O zero and not 10 -7 ? liquids such as water are not included in c...

RichBollini4G

Jamie Hwang 2F wrote:
RichBollini4G wrote:Does anyone know if the homework is graded for completion or for correctness?

It's really up to your TA. My TA grades for completeness because we have the right answers in the Solutions Manual but you should ask your TA if you're not sure.

Thank you

RichBollini4G

Patricia Cardenas wrote:
RichBollini4G wrote:Does anyone know if the homework is graded for completion or for correctness?

It depends on your TA, last quarter my homework was graded on correctness.

Thank you

RichBollini4G

K doesn't have units because because the products and reactants have the same units so they can cancel out. But if it doesn't cancel out, instead of thinking of concentration or partial pressure, consider transition of reactants to products as activity, which is unitless, so K is unitless Thank you!

RichBollini4G

When do you use Q and when do you use K? What are the differences between them? K is the equilibrium constant. Q is calculated the same way as K, but it can be used at any time - regardless of if the reaction is at equilibrium or not. By comparing the two, you can find the direction the reaction is...

RichBollini4G

Yes; when solving for Q, you write the expression in the same exact way you would for K, omitting pure liquids and solids. The central difference between Q and K is that K represents the value at equilibrium, while Q is the ratio of products to reactants at any time during the reaction. But you wou...

RichBollini4G

SarahCoufal_1k wrote:everything on sapling learning is voluntary and just an extra resource I believe

Thank you!

RichBollini4G

Does anyone know if the homework is graded for completion or for correctness?

RichBollini4G

Natalie Nartz 4F wrote:Homework problems from the textbook are due in during your discussion time. Posts on chemistry community are due 11:59 pm Sunday night.

Thank you!!

RichBollini4G

1. Water can't act as a polydentate because it is too small to form multiple bonds to a transition metal central atom. The lone pairs are both on the same O atom. 2. Carbonate can act as both mono and bidentate. Since it has two O atoms with - charge (lone pairs), it can interact in two places. It ...

RichBollini4G

Alvaro Chumpitaz 4D wrote:Are there any exceptions to the electronegativity periodic trend?

none except the nobles gases.

RichBollini4G

Oxygen is an exception to the trend because it is easier for oxygen to give up an electron to have a more stable configuration than it is for nitrogen to give up an electron. This is because nitrogen has three electrons in the p orbital, which is relatively more stable than the four electrons oxyge...

RichBollini4G

Kavya Immadi 3D wrote:Ionization energy is the energy needed to remove electrons from atoms. Electronegativity is how much an atom attracts electrons.

very helpful

RichBollini4G

Will we have to know general electronegativity trends for this upcoming midterm? I haven't fully solidified my concept of it yet and was wondering how much of it will be necessary for the midterm. yes, however we will most likely just need to know that electronegativity increases as you move up and...

RichBollini4G

The s-, p-, d-, and f- orbitals designate the shapes of the mathematical functions predicting the locations of electrons in atoms. The s- orbital has a spherical shape with no nodal planes and symmetric distribution, the p-orbital has two lobes on either side of the nucleus, d- orbital has three 4-...

RichBollini4G

Anokhi Patel 4G wrote:We can use atomic radii to determine the strength of the attraction of electrons to the atom compared how well the nucleus holds the electrons together.

Very helpful!

RichBollini4G

Electron affinity is the likelihood of an atom gaining an electron. Since Nitrogen's 2p shell is has 3 up-spin electrons, making it half full, it would not want to take on another electron because it would make the atom less stable. Half full and completely full subshells are more stable than parti...

RichBollini4G

kendal mccarthy wrote:I think as long as you know the general trends of electronegativity that should suffice. If there are weird patterns that might not seem obvious my TA said the test would include numbers of electronegativity to help.

Thank you, very helpful!

RichBollini4G

I don't think there can a trend on the periodic table for isoelectronegativity since it's comparing the amount of electrons for different molecules. O^2- is isoelectric with Neon because they both have 10 electrons. In terms of atomic size in an isoelectric series, the more protons there are the sm...

RichBollini4G

AngieGarcia_4F wrote:I think you could relate it to chelating ligands because a ligand cant create a ring around a metal if it cant rotate meaning it would have to have the right type of bond (single vs double) in the right places.

Thank you, this was helpful

RichBollini4G

Chloe Alviz 3F wrote:In the textbook, it says that all single covalent bonds are sigma bonds. If this is the case, how would we define the bond for an ionic compound such as NaCl?

It would just be defined as an ionic bond.

RichBollini4G

905174774 wrote:FOr pi bonds, a triple bond is considered one sigma bond and two pi bonds right?

yes!

RichBollini4G

Jessica Tejero 3L wrote:Write the names of the ligands in the following order: neutral, negative, positive. If there are multiple ligands of the same charge type, they are named in alphabetical order.

Awesome, thank you

RichBollini4G

Haley Dveirin 4B wrote:I would just to be safe. I think you should know all the VSEPR shapes listed on the worksheet handed out in your discussion section which includes those.

Is there anywhere we can find a copy of that sheet online?

RichBollini4G

Sara Richmond 1D wrote:Sigma bonds are single bonds. Pie bonds are in double and triple bonded atoms. In a double/ triple bonded atom, one bond is always a sigma bond and the others are pie bonds.

Thank you!

RichBollini4G

Linear 180 Trigonal Planar 120 Bent (varies based on which formula it is, if its AX2E2 then its less than 109.5, if its AX2E then its less than 120) Tetrahedral 109.5 Trigonal Pyramidal less than 109.5 Trigonal Bipyramidal 90 and 120 See Saw less than 90 & less than 120 T-shaped less than 90 &a...

RichBollini4G

It's hard to say which ones will be on the test and the exam, but I'd say definitely any shape that Lavelle has shown us in lecture as well as any that appear in the homework. But everything on the chart below would be a good thing to memorize, just to be safe. https://www.google.com/url?sa=i&s...

RichBollini4G

How can we tell when a bond is a Pi or Sigma bond?

RichBollini4G

Do we need to know this for Test 2?

RichBollini4G

lauraxie3d wrote:When do I use wedge and dash to draw models? For example CH4 in class we drew it using wedge and dash, but SF6 we didn't?

The wedge and dash are used to show the VSEPR 3D structures of molecules/molecular geometry.

RichBollini4G

NicoJones_1B wrote:If our molecule does not have any lone pairs when writing the notation do we write E0 or just not write E at all?

i don't believe you need to include E0

RichBollini4G

The VSEPR model gives you the electron geometry and molecular shape. The electron geometry of a molecule is the naming convention based on the number of electron regions. Molecules with 2 electron regions are linear, 3 electron regions are trigonal planar, 4 electron regions are tetrahedral, 5 elec...

RichBollini4G

In VSEPR, double and triple bonds would still be represented as “single” bonds demonstrably. Lavelle even said that we should think of these spaces as possible spots of electron density where said density of electrons is highest. This is for VSPER models specifically. thank you, this was very helpful

RichBollini4G

Alexis 3F wrote:This test will only range from what we've learned since the midterm up until the first 5 minutes of class on monday

Do you know what sections in the book that covers?

RichBollini4G

Both sigma and pi bonds are covalent bonds and form by overlap of atomic orbitals. Sigma bonds are formed by end-to-end overlapping and Pi bonds are when the lobe of one atomic orbital overlaps another. Generally sigma bonds are stronger than pi bonds. They can occur in the same molecule. Thank you...

RichBollini4G

Sana_Mian_3G wrote:If there is a triple bond how many pi and sigma bonds are there?

1 sigma and 2 pi bonds

RichBollini4G

For a more in-depth analysis of your question, I would take a look at this article: https://brilliant.org/wiki/sigma-and-pi-bonds/ Understanding the difference between sigma and pi bonds is important in understanding the molecular orbital theory, which will in turn help you with structural and orbi...

RichBollini4G

VLi_1L wrote:Why are single bonds longer than double bonds?

The attraction is stronger in the double bond, since there are more electrons, which pulls the atoms closer together, causing the bond length to be shorter than a single bond.

RichBollini4G

Kennedi3K wrote:Is this the same for ionization energy?

Yes!

RichBollini4G

Kendra Barreras 3E wrote:Both electronegativity and ionization energy increases from left to right. The same is true for electron affinity. the opposite however is true for the atomic radius.

Thank you!

RichBollini4G

Jaklin Astvatsatryan wrote:guys i really recommend watching videos, esp my visual learners. start problems and try doing them without notes and then watch videos if you're really stuck.

this really helped me, thank you!

RichBollini4G

I know that in the course reader it says to read chapter 5 for a review for gases. But every time i try reading the textbook i get intimidated and i stop reading the textbook . Do you guys find it more helpful when you guys read the textbook? Yes, although I would agree sometimes it is confusing, i...

RichBollini4G

I noticed there are some differences between edition 6 and edition 7 of the book, the first parts were similar but now it is become more and more different, can edition 6 still work?

RichBollini4G

Does anyone know what sections we can turn in for homework number 5?

RichBollini4G

Thank you all, this all really helped.

RichBollini4G

Does anyone know what section problems we should be turning in for homework #4? Is it still quantum?

RichBollini4G

Gilberto Millan 1F wrote:
RichBollini3C wrote:Does anyone know how to see how many posts you have posted?

Yes, you go to the top right and click on your username->click on control panel->click on overview->go to the bottom of the page and it should say something like "My Posts."

Thank you so much, this worked!

RichBollini4G

Lizette Noriega 1H wrote:
RichBollini3C wrote:
Diana Chavez-Carrillo 3J wrote:Are the TA's grading our homework based on completion or correctness?

I believe they are grading based on correctness.

Do you know if all the TAs grade based on correctness or does it vary from TA to TA?

I believe it varies because I know some TAs that are grading based on solely completion.

RichBollini4G

ktran Disc 1I wrote:Is it recommended to just show all of our work when possible? Also, do we need to include the specifications for the element/compound in our calculations?

I think the safe bet is to always show every step with the specifications for an element or compound just in case.

RichBollini4G

Diana Chavez-Carrillo 3J wrote:Are the TA's grading our homework based on completion or correctness?

I believe they are grading based on correctness.

RichBollini4G

Angela Prince 3B wrote:Does anyone know if we will be on the quantum topic for more than just one week? I just want to know if the homework set for quantum will be used for both weeks 3 and 4. Thanks!

I think since we are learning about quantum topics for a couple of weeks it should be used for both week 3 and 4.

RichBollini4G

Maya Beal Dis 1E wrote:Since the Quantum Unit is more than a week long does it mean we just hand in five homework problems from that section every week until we are done with the unit?

I also was confused about this, will he tell us what sections we should be doing each week?

RichBollini4G

He specified to do either fundamentals or quantum world for homework 2. Would there be any benefit to do one or the other, such as if one would better prepare us for a test or quiz? Doing the fundamentals problems for homework 2 would probably be the best preparation for the test since quantum is n...

RichBollini4G

Thank you so much. Life saver.

RichBollini4G

Thank you so much for your advice! This is going to help me a lot this year!

RichBollini4G

Does anyone know how to see how many posts you have posted?

RichBollini4G

I think we need to bring a non-graphing calculator, i'm not sure if we are going to be given a periodic table or not though.

RichBollini4G

Thank you so much for sharing your story! It is super interesting to hear first hand what your experience was like!

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