## Search found 79 matches

Tue Jan 26, 2021 4:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sapling #5
Replies: 5
Views: 23

### Sapling #5

Consider these reactions, where M represents a generic metal. 1. 2M(s)+6HCl(aq)⟶2MCl3(aq)+3H2(g) ΔH1=−802.0 kJ 2. HCl(g)⟶HCl(aq) ΔH2=−74.8 kJ 3.H2(g)+Cl2(g)⟶2HCl(g) ΔH3=−1845.0 kJ 4.MCl3(s)⟶MCl3(aq) ΔH4=−210.0 kJ Use the given information to determine the enthalpy of the reaction: 2M(s)+3Cl2(g)⟶2MCl...
Mon Jan 25, 2021 5:46 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Textbook Problem 6E.1
Replies: 2
Views: 16

### Textbook Problem 6E.1

Can someone remind me again what the difference between the first ionization and second ionization is? I'm looking at problem 6E.1 and I'm having a hard time understanding what it is saying/how to go about the question since I think if you look at the table, it only gives Ka2 & pKa2 "Calcul...
Mon Jan 25, 2021 5:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6d.15 textbook
Replies: 3
Views: 16

### Re: 6d.15 textbook

Wait for part A do you just disregard the Cl part of the NH4Cl because in the solution manual it just has NH4+. Or how would go approaching this problem?
Mon Jan 25, 2021 4:03 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Percent Ionization and Percent Protonation
Replies: 1
Views: 22

### Percent Ionization and Percent Protonation

What are the equations for finding the percent ionization and percent protonation? And are there any tricks you guys have for memorizing what ionization vs protonation does? Thanks!
Sun Jan 24, 2021 4:33 pm
Forum: Student Social/Study Group
Topic: CHEM 14B Midterm 1 Notes
Replies: 22
Views: 119

### Re: CHEM 14B Midterm 1 Notes

This will be so helpful! Thank you so much for sharing :). Goodluck on the midterm!!
Sun Jan 24, 2021 1:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Problem 5I.15
Replies: 1
Views: 18

### Textbook Problem 5I.15

Can someone explain why the change for NH3 would be +x instead of -x? I thought it would be 0.200+ x, but it seems both Nh3 and H2S will change with +x When solid NH4HS and 0.400 mol NH3(g)were placed in a vessel of volume 2.0 L at 24 °C, the equilibrium NH4HS(s)⇌NH3(g)+H2S(g), for which Kc=1.6×10−4...
Sat Jan 23, 2021 1:29 pm
Forum: Student Social/Study Group
Topic: Study Guide - Midterm?
Replies: 14
Views: 55

### Study Guide - Midterm?

Hi! Has anyone made or found a study guide for this upcoming midterm that was really useful for them that they would be willing to share/recommend? I feel like I don't have a super concreate foundation on what we've been learning, and it would mean a lot to me if someone could share a resource :). T...
Sat Jan 23, 2021 12:19 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Sapling Question 5
Replies: 1
Views: 25

### Sapling Question 5

The Kb for an amine is 3.227×10−5. What percentage of the amine is protonated if the pH of a solution of the amine is 9.786? Assume that all OH− came from the reaction of B with H2O. I keep getting 52.82% as my answer but I could be completely off ahah. Can someone please tell me what they got as th...
Wed Jan 20, 2021 5:50 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: sapling #3
Replies: 5
Views: 39

### sapling #3

Can someone help me with this problem? For some reason, I am not sure where to start: Muscles produce lactic acid, CH3CH(OH)COOH(aq) , during exercise. Calculate the percent ionization (deprotonation), pH, and pOH of a 0.1173 M solution of lactic acid. The acid‑dissociation (or ionization) constant,...
Sun Jan 17, 2021 9:54 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling WK 1, #4
Replies: 3
Views: 23

### Re: Sapling WK 1, #4

You are going to want to start with the ICE table and use the initial bar pressure of PCl5 in the beginning, with the other two at 0. Then at equilibrium you would set the equation equal to the Kp that was given. You should be able to do the quadratic formula and solve for x and then plug it back in...
Fri Jan 15, 2021 5:09 pm
Forum: Student Social/Study Group
Topic: Approaching Outlines
Replies: 14
Views: 38

### Approaching Outlines

I was wondering how you guys approach doing the outlines? I know the textbook problems are very useful and so I want to do them, but do you guys complete them as we are learning them or at the end of the weeks? I think I'm just feeling a little overwhelmed since we're definitely moving a lot faster ...
Fri Jan 15, 2021 5:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Week 1 #9
Replies: 3
Views: 18

### Re: Sapling Week 1 #9

Hi! What I did was since you are given the equilibrium values, you can immediately find the Kc by plugging the the products/reactants. Then to set up the ICE table, you would put the other two's values that did not change as the I and the I for the changed molecule as the new change valued. Then you...
Mon Jan 11, 2021 6:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: sapling question 3
Replies: 2
Views: 26

### Re: sapling question 3

The equilibrium constant would be Kc=[HI]^2/[H2][I2]. When you express Kc in terms of x it would be 53.3=(2x)^2/(0.800-x)^2, which equals 7.30=2x/(0.800-x). If you solve the equation x equals 0.628M. Since [HI] is 2x, 2(0.628M) will result in 1.256M. Oh I totally forgot to also square root the 53.3...
Mon Jan 11, 2021 5:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: sapling question 3
Replies: 2
Views: 26

### sapling question 3

Hi! Would someone be able to help me with this problem? For some reason I keep getting 1.542 as the answer, but I guess it isn't right. At a certain temperature, the equilibrium constant, Kc, for this reaction is 53.3. H2(g)+I2(g)↽−−⇀2HI(g)Kc=53.3 At this temperature, 0.800 mol H2 and 0.800 mol I2 w...
Sun Jan 10, 2021 10:54 am
Forum: General Science Questions
Topic: step up sessions
Replies: 11
Views: 124

### Re: step up sessions

Hi :) Is each step up session different? Like do they go over different problems in each session? Yes! Each UA puts together their own worksheet, so the content of each session will be based on what they want to do. I haven't found any of the sessions to have the same practice problems, so it's bee...
Sun Jan 10, 2021 10:51 am
Forum: Administrative Questions and Class Announcements
Topic: 14B Midterm Content
Replies: 4
Views: 41

### Re: 14B Midterm Content

Hi! I'm not completely sure, but I would assume that we would just be tested on 14B content that we learn in these coming weeks since we are taking this class, and not 14A. If there would be anything from 14A, it would probably be the last part of what we learned last quarter, as it overlaps a bit.
Tue Jan 05, 2021 10:20 pm
Forum: Administrative Questions and Class Announcements
Replies: 36
Views: 188

### Re: Question about 14B Exams

Yes! Midterms will be given on a Friday during your lecture time, instead of discussion times like 14A. I believe one of the UAs said that this was probably so that everyone takes it on the same day instead of it being scattered around. The final should be on a Sunday though.
Tue Jan 05, 2021 10:42 am
Forum: Administrative Questions and Class Announcements
Topic: Chemistry Posts in 14B [ENDORSED]
Replies: 125
Views: 1901

### Re: Chemistry Posts in 14B[ENDORSED]

Hi! This is my first time using Chemistry Community, and I just wanted to clarify something---will we be posting all questions/answers here? Or are there different links we need to go to to ask different types of questions (like homework-specific questions)? Thanks in advance! Post everything here....
Mon Jan 04, 2021 6:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium vs Initial Concentration
Replies: 5
Views: 21

### Equilibrium vs Initial Concentration

Hi! Can someone clarify the difference between an equilibrium constant vs initial concentration? Specifically I was looking at the modules posted on the website and for part 1A, #17 says "for a balanced chemical equation with all stoichiometric coefficients equal to one, what is the simplest ex...
Wed Dec 09, 2020 9:55 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acidity Stronger
Replies: 3
Views: 38

### Acidity Stronger

I'm still a bit confused on what to look at to tell if an acid is stronger or not (besides memorizing the strong acids). When would we look at the bond strength and when would we look at electronegativity? And within electronegativity, why is that the polar it is then the stronger acidity it is?
Wed Dec 09, 2020 9:44 am
Forum: Determining Molecular Shape (VSEPR)
Topic: TA Review
Replies: 3
Views: 61

### Re: TA Review

I think he said yesterday in the session that you had to email him and ask for it.
Tue Dec 08, 2020 9:47 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Geometry & Electron Density
Replies: 5
Views: 32

### Molecular Geometry & Electron Density

Hi! I am a little confused on the difference between molecular geometry and electron density, and when to use them. I noticed in the textbook it says to "find the shape" but does not specify which one. What is the difference between the two and which one do we normally find in regards to l...
Tue Dec 08, 2020 9:38 am
Forum: Significant Figures
Topic: Things to remember for final?
Replies: 20
Views: 145

### Re: Things to remember for final?

I would suggest memorizing the strong acids/bases, so that in case there is a question about it (i can forsee him throwing one or two), then it would be easier to use process of elimination.
Mon Dec 07, 2020 8:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Textbook 2E 5
Replies: 2
Views: 8

### Re: Textbook 2E 5

For this question, how come the solution manual says that it would be trigonal planar? Because wouldn't the shape be bent? Unless the solution manual is referring to the electron geometry... but are we usually asked for electron geometry?
Mon Dec 07, 2020 3:06 pm
Forum: Administrative Questions and Class Announcements
Topic: TA review sessions [ENDORSED]
Replies: 4
Views: 74

### Re: TA review sessions[ENDORSED]

I was also confused on both times, but I just found out that the time in the parenthesis is the normal office hour time, and the other time is when the review session is.
Mon Dec 07, 2020 10:25 am
Forum: Lewis Acids & Bases
Topic: Week 10 Sapling #6
Replies: 2
Views: 33

### Week 10 Sapling #6

Hi ! Can someone help me classify which compounds are strong acids, weak acids, strong bases, weak bases, and others? I've tried a couple times, but can't seem to get the right answer.

HNO3, HI, H2CO3, HCN,CH3COOH, NaOH, Ba(OH)2, NH3, (CH3)2NH, NaCl
Sat Dec 05, 2020 10:48 am
Forum: Administrative Questions and Class Announcements
Topic: Lavelle's Review Sessions
Replies: 3
Views: 56

### Re: Lavelle's Review Sessions

I was also wondering the same thing! I think though at least for his Wednesday one, it will probably be at 5-6pm PST because that's when his normal discussion section is.
Thu Dec 03, 2020 5:20 pm
Forum: Naming
Topic: Sapling 1
Replies: 3
Views: 36

### Sapling 1

What would the name of [Co(NH3)3Cl3] be? And how did you come to that conclusion?
Thu Dec 03, 2020 3:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Chart
Replies: 4
Views: 54

### Re: VSEPR Chart

this video also helped me a lot if you want to check it out!
https://youtu.be/Q9-JjyAEqnU
Thu Dec 03, 2020 3:36 pm
Forum: General Science Questions
Topic: Video for topic review suggestions
Replies: 5
Views: 50

### Re: Video for topic review suggestions

For me, if you look on youtube, the Organic Chemistry Teacher has been really helpful for a wide range of topics! Also Khan Academy haha.
Wed Dec 02, 2020 8:48 am
Forum: Naming
Topic: Lecture Example [Co(Nh3)5 Cl]Cl2H2O
Replies: 8
Views: 52

### Re: Lecture Example [Co(Nh3)5 Cl]Cl2H2O

When naming, within the brackets does it matter the order of which one goes first, second,etc?
Tue Dec 01, 2020 4:53 pm
Forum: Administrative Questions and Class Announcements
Topic: Trouble logging into Chem 14A website [ENDORSED]
Replies: 5
Views: 99

### Re: Trouble logging into Chem 14A website[ENDORSED]

No problem! However, on a side note, does anyone have trouble when logging in to the chemistry community web page? When I log in, it always says that my account isn't created, so I have to keep registering under the same alias. Does anyone else have the same problem? Hmmm that is weird. For me, I j...
Tue Dec 01, 2020 4:51 pm
Forum: Administrative Questions and Class Announcements
Topic: Final exam (fall 2020 quarter)
Replies: 20
Views: 233

### Re: Final exam (fall 2020 quarter)

In the email Lavelle sent, on the attachment when it said that there will be problems that come from homework, is that referencing textbook problems or sapling problems?
Sat Nov 28, 2020 12:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #18
Replies: 1
Views: 38

### Sapling #18

I'm having a hard time understanding this... could someone explain?

-Why do the hydrogen atoms of H2CCH2 and H2CCCCH2 lie in the same plane?
-Why is it true that if the X is an even number in the general form H2C(C)x CH2, then the hydrogens are coplanar?
Sat Nov 28, 2020 11:00 am
Forum: Ionic & Covalent Bonds
Topic: lone pairs -polar molecule
Replies: 10
Views: 105

### lone pairs -polar molecule

If any of the elements within the atom have a lone pair, could you automatically assume that it is a polar molecule?
Thu Nov 26, 2020 11:11 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Axial/equatorial
Replies: 4
Views: 14

### Re: Axial/equatorial

How would you be able to tell which is the axial vs which is the equatorial if you are able to rotate it?
Wed Nov 25, 2020 12:56 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem 14B Lectures
Replies: 15
Views: 140

### Re: Chem 14B Lectures

I believe in his recent email he said there could be tests/midterms during lecture times for Chem14B. But if he only does 2 midterms again during lecture times, you could technically just sacrifice your other class 2 times if it overlaps a little.
Wed Nov 25, 2020 9:00 am
Forum: Sigma & Pi Bonds
Topic: Reason for double bonds being sigma/pi
Replies: 2
Views: 20

### Re: Reason for double bonds being sigma/pi

The very simplistic way I think of it, is a sigma bond is a single bond. So when there is a double bond, or triple bond something else needs to fill it. So for a double bond, you can always start out with the sigma bond (single) and then however many more bonds you need will be the pi bonds. Therefo...
Tue Nov 24, 2020 4:34 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 Scores
Replies: 9
Views: 95

### Re: Midterm 2 Scores

Did you guys do better or worse compared to the first one??
Mon Nov 23, 2020 7:21 pm
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 337
Views: 139732

### Re: Saying Thank You to Dr. Lavelle

Hi Dr. Lavelle!

I just wanted to say thank you for taking the extra effort to make some of us freshmen feel like we are in the big lecture hall learning chemistry. I know it takes a lot of energy to also get tested and make sure it is a safe environment, so just wanted you to know we appreciate it!
Sat Nov 21, 2020 9:02 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Exercise 2A.5
Replies: 3
Views: 31

### Re: Exercise 2A.5

Oh that is a good point, I did not even think of counting 15... I just looked at it that the f subshell has 14 orbitals, so that would be the amount of space one could fill.
Wed Nov 18, 2020 1:25 pm
Forum: Student Social/Study Group
Topic: Reviewing Midterm Questions
Replies: 1
Views: 26

### Reviewing Midterm Questions

Hi! Do you know if Lavelle will be going over each midterm problem in preparation for the final or if there is a way for us to see which ones we got wrong and right? I feel like individually knowing what I got wrong can help me fix these mistakes so I can do better for the final, as I didn't feel su...
Wed Nov 18, 2020 1:22 pm
Forum: Student Social/Study Group
Replies: 110
Views: 1177

Also, someone mentioned above that Lavelle is dropping 10 points from the first midterm to make it out of 100 rather than out of 110, does anyone have more information to confirm/deny this? I think someone said in the GroupMe that they went to his office hour one time and he said that was false. Ho...
Wed Nov 18, 2020 1:19 pm
Forum: Student Social/Study Group
Replies: 29
Views: 310

### Re: Grading Scale for Chem14A

I'm not exactly sure, I mostly try to estimate my grade based on the points I'm receiving (like getting points for chemistry community, the hw, etc). And then based on how my midterms go, I try to see what range I'm in (like whether I'm passing or not lol). I don't think Lavelle has specifically sa...
Wed Nov 18, 2020 9:20 am
Forum: Quantum Numbers and The H-Atom
Topic: Outline 2 - properties of electrons
Replies: 2
Views: 59

### Re: Outline 2 - properties of electrons

Hmm I think you should be correct in terms of properties. I think it would probably be important as well to know the relationship between how many orbitals are in the s,p,d, and f to the number of electrons each can carry, such as if there are unpaired electrons, etc.
Tue Nov 17, 2020 5:53 pm
Forum: Trends in The Periodic Table
Topic: Textbook Problem 1.13
Replies: 2
Views: 52

### Textbook Problem 1.13

Can someone explain to me the answer for this: "Ionization energies usually increase on going from left to right across the periodic table. The ionization energy for oxygen, however, is lower than that of either nitrogen or fluorine. Explain this anomaly." Also, is oxygen just an exception...
Mon Nov 16, 2020 11:39 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Unpaired Electrons
Replies: 2
Views: 26

### Unpaired Electrons

Hi! Does anyone have any tips for how to determine the number of unpaired electrons quicker? Right now I am looking at Textbook Problem 1E #23, when it asks for Ga, Ge, As, Se, Br and I'm not sure how off the top of my head to think about how many unpaired electrons each would have.
Wed Nov 11, 2020 4:25 pm
Forum: Ionic & Covalent Bonds
Topic: Ions
Replies: 6
Views: 34

### Re: Ions

For the nitrite ion (NO2-), why is it that there is only one double bond from N to one of the Os? And how would you know before doing the formal charges?
Tue Nov 10, 2020 5:44 pm
Forum: Bond Lengths & Energies
Topic: Hydrogen Bonding
Replies: 6
Views: 55

### Re: Hydrogen Bonding

Hydrogen bonds are attractions between a hydrogen and an electronegative atom. This happens because of the difference in electronegativity. Whereas on the other hand, covalent bonds are more about the sharing of electrons, so the electronegativities are relatively the same. Hydrogen bonds are weak b...
Tue Nov 10, 2020 5:39 pm
Forum: Administrative Questions and Class Announcements
Topic: 14B Next Quarter
Replies: 8
Views: 131

### Re: 14B Next Quarter

I remember Lavelle saying for this class (14A) that he let everyone off the waitlist, but i do not think he specifically mentioned anything for 14B. I would assume it would be the same way because on the class planner, if I remember correctly, Lavelle is only teaching 14B, not A. So, I would say tha...
Tue Nov 10, 2020 5:31 pm
Forum: Dipole Moments
Topic: Polar vs Nonpolar
Replies: 3
Views: 21

### Re: Polar vs Nonpolar

In order to see if it is a nonpolar molecule or a polar molecule, you would need to look at the electronegativities of each atom. If the two atoms have the same electronegativity, then the electrons are equally shared because they are pulled on the same. However, if one atom has a higher electronega...
Tue Nov 10, 2020 5:26 pm
Forum: Bond Lengths & Energies
Topic: Dissociation Energy Trend
Replies: 2
Views: 25

### Re: Dissociation Energy Trend

Like Jonathan said above, dissociation energy is not necessarily a trend, but rather you can come to the conclusion through trends. For example, a big factor would be the size of the atom because that would determine the bond lengths, and further, the dissociation energy. Thus you could take into co...
Tue Nov 10, 2020 5:21 pm
Forum: Bond Lengths & Energies
Topic: Dipole
Replies: 7
Views: 23

### Re: Dipole

How would you know when there is an induced dipole? Does an induced dipole always happen?
Thu Nov 05, 2020 8:03 am
Forum: Ionic & Covalent Bonds
Topic: Size of Bonds
Replies: 28
Views: 101

### Size of Bonds

Can someone explain in simple terms why double bonds are shorter than single bonds?
Wed Nov 04, 2020 6:32 pm
Forum: Lewis Structures
Topic: Central atom
Replies: 4
Views: 34

### Re: Central atom

If I remember correctly, usually the atom with the lowest ionization energy will be in the center. This is because if you think about it in other terms, low ionization energy means it would require the largest number of electrons to complete its octet. Thus, it would make sense for it to be in the m...
Wed Nov 04, 2020 6:21 pm
Forum: Octet Exceptions
Replies: 7
Views: 48

I could be wrong, but I would assume that we do not have to memorize them because I feel like Lavelle emphasizes that you can come to the conclusion of something by using previous knowledge of characteristics of each element.
Tue Nov 03, 2020 5:01 pm
Forum: Trends in The Periodic Table
Topic: Inert-pair effect
Replies: 4
Views: 43

### Re: Inert-pair effect

I believe that inert pair effect is common in the 15-17th group elements and usually is it because the inertness of the inner electrons do not have good shielding. But, I am also wondering the same thing because I do not know much about this topic.
Tue Nov 03, 2020 4:58 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8548
Views: 1474866

### Re: Post All Chemistry Jokes Here

The optimist sees the glass half full. The pessimist sees the glass half empty. The chemist sees the glass completely full, half with liquid and half with air.

If the Silver Surfer and Iron Man team up, they’d be alloys.
Mon Nov 02, 2020 9:40 am
Forum: Administrative Questions and Class Announcements
Topic: Chem 14B Enrollment
Replies: 27
Views: 313

### Chem 14B Enrollment

If I remember correctly, Lavelle said that he accepts everyone off the waitlist. Do you guys think it would be smart to enroll in CHEM14B with the second pass then? Or how are you guys approaching enrollment?
Sat Oct 31, 2020 9:23 am
Forum: Administrative Questions and Class Announcements
Topic: When do homework grades update in CCLE?
Replies: 4
Views: 26

### Re: When do homework grades update in CCLE?

To check my grades I go through the UCLA website under the class tab because I think it updates faster than the CCLE app. Under the class tab, where are you able to check grades through UCLA's website? Because I only see things such as "change grade type", "change units", etc......
Wed Oct 28, 2020 1:01 pm
Forum: Administrative Questions and Class Announcements
Topic: Other TA's office hours
Replies: 2
Views: 22

### Re: Other TA's office hours

It should be on Lavelle's chemistry website, and then you scroll down to Course Materials, and there will be different links for the different TAs. You can see links with "TA Office Hours & Discussion Sections Lecture 1", etc for each lecture, or there should be another link right unde...
Wed Oct 28, 2020 12:58 pm
Forum: Administrative Questions and Class Announcements
Topic: Chemistry Modules
Replies: 7
Views: 58

### Chemistry Modules

Do you know if Lavelle will continue posting the modules on his class website for the next units that we will be learning? I find them to have really helped with these past couple ones, especially being able to do more practice problems and seeing the correct answer. It also was good to try the prob...
Wed Oct 28, 2020 12:55 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem 14BL
Replies: 5
Views: 96

### Re: Chem 14BL

Going off what John said above, my friends who have taken BL highly suggest taking it along side C, or after you have taken B. It is manageable to take it with B, but I just heard that it is easier to get a grasp of what is going on in the lab because you already learned the material. Also, I believ...
Mon Oct 26, 2020 11:15 am
Forum: Limiting Reactant Calculations
Topic: What counts as theoretical yield?
Replies: 8
Views: 79

### What counts as theoretical yield?

When finding the percent yield, is theoretical yield only the amount of the limiting reactant? For some reason I thought you would add the product's grams that came from both the reactants and that was the theoretical yield...
Fri Oct 23, 2020 6:17 pm
Forum: Properties of Electrons
Topic: Understanding energy transitions
Replies: 4
Views: 44

### Understanding energy transitions

For some reason I am having a difficult time understanding this. I know that the higher energy it is, the shorter wavelength, and the shorter energy, the longer the wavelength. But how do you apply this to when looking at energy levels. For example, on sapling it says "the range of wavelengths ...
Thu Oct 22, 2020 6:02 pm
Forum: Properties of Light
Topic: Units for wavelength/frequency
Replies: 18
Views: 96

### Units for wavelength/frequency

Can someone clarify what units wavelengths and frequency are usually measured in? Also do you think on the midterm if the question does not specifically say, for example, " state the wavelength in nanometers", could you leave it in the unit that is not commonly used, and get full points?
Thu Oct 22, 2020 3:09 pm
Forum: Photoelectric Effect
Topic: Textbook Problem 1A. 9
Replies: 4
Views: 45

### Textbook Problem 1A. 9

Can someone walk me through their thinking process to how they would know what the event is based on the other given information? A college student recently had a busy day. Each of the student’s activities on that day (reading, getting a dental x-ray, making popcorn in a microwave oven, and acquirin...
Wed Oct 21, 2020 8:46 am
Forum: Administrative Questions and Class Announcements
Topic: Respondus Setup factored in Midterm time?
Replies: 2
Views: 26

### Respondus Setup factored in Midterm time?

Hi! I took the practice quiz for the midterm today in my discussion and when going through the beginning of the Respondus, we had to go through the steps of taking a picture, environment check, etc. Do you know if this factors into the 50 min time to take the midterm next week? Or does the midterm t...
Mon Oct 19, 2020 4:56 pm
Forum: DeBroglie Equation
Topic: Post Assessment #34
Replies: 1
Views: 21

### Post Assessment #34

Can someone explain how to go about this problem/what the answer is? For some reason when working it out, I keep getting a large number and I'm pretty sure I am inputting it into my calculator correctly. I multiplied the mass times the wavelength and then divided the answer by Plank's Constant in or...
Thu Oct 15, 2020 10:54 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post Module - #41
Replies: 2
Views: 39

### Atomic Spectra Post Module - #41

Hi! Can someone explain to me how to go about the process of elimination within this problem? The question is "for the hydrogen atom which statement is true" A. The transition from n=5 to n=3 involves greater energy than one from n=4 to n=2. B. The transition from n=4 to n=2 emits radiatio...
Thu Oct 15, 2020 5:06 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Delta E
Replies: 5
Views: 55

### Delta E

I am currently watching the Atomic Spectra Video Module, and wanted some clarification. Delta E would technically be equal to E right? Because if Delta E is the difference in energy level and E is the energy of the photon, then the two should match?
Wed Oct 14, 2020 5:13 pm
Forum: Properties of Light
Topic: Photoelectric Effect -Post Assessment #23
Replies: 2
Views: 20

### Photoelectric Effect -Post Assessment #23

The question says "to interpret the results of photoelectric experiments the model of light needs to change from a ____ model to a ____ model. What are the two missing words?" I thought the correct answer was wave model to photon model. I think someone else said it would be a wave model to...
Wed Oct 14, 2020 12:26 pm
Forum: Properties of Light
Topic: Light intensity for electron ejection
Replies: 7
Views: 65

### Re: Light intensity for electron ejection

Question... I thought before we saw in the Photoelectric Effect that increasing intensity does not work to eject electrons because it is not acting like a wave model. Here, are we talking about the intensity of a wavelength then? Because in the most recent lecture, we see that increasing light inten...
Mon Oct 12, 2020 5:59 pm
Forum: Administrative Questions and Class Announcements
Topic: Quizzes in Discussion Sections?
Replies: 6
Views: 82

### Quizzes in Discussion Sections?

Can someone clarify if we have quizzes in this class? I hear people mention our TAs will be giving quizzes at the beginning of discussion sections, but I do not see anything mentioned in the syllabus. Please correct me if I am wrong. Thank you! :)
Wed Oct 07, 2020 5:29 pm
Forum: Empirical & Molecular Formulas
Topic: Sampling Question #8
Replies: 5
Views: 78

### Sampling Question #8

When looking at a chemical structure (like the one in this problem), will it always portray the molecular formula? Or will it sometimes display the empirical formula and you would have to figure out which of the two it is based on the picture? Because in this problem, I just counted how many of each...
Tue Oct 06, 2020 10:24 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Chemical Formulas of Compounds
Replies: 9
Views: 136

### Chemical Formulas of Compounds

Hi! Do you guys think when given a name of a compound, we should automatically know the chemical formula for it? For example, being able to know the formula for fluoxetine (I saw this compound in the textbook). If so, do you have tricks/tips to remembering how to name the compound? Thanks!
Mon Oct 05, 2020 4:53 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Average Mass
Replies: 3
Views: 48

### Average Mass

When finding the average mass, why do we have to divide the molar mass by Avogadro's number? I understand that it is the average since there are multiple isotopes, but WHY Avogadro's number? For example, I'm doing the textbook problem, E27, and part A asks to find the mass of H2O. I first found the ...
Mon Oct 05, 2020 4:01 pm
Forum: SI Units, Unit Conversions
Topic: Chemistry 14A Exam format
Replies: 5
Views: 97

### Re: Chemistry 14A Exam format

I'm not entirely sure, maybe he will mention the format when it gets closer to the actual date of the midterm/final. However, I do know he mentioned that he will be taking some of the hw problems from the textbook on the syllabus and putting it on the tests. So make sure to do those!
Mon Oct 05, 2020 3:27 pm
Forum: Empirical & Molecular Formulas
Topic: Formula Units vs Empirical Formula
Replies: 4
Views: 65

### Formula Units vs Empirical Formula

Can someone explain the difference between formula units and empirical formulas? I think I'm just confused on exactly what formula units are...