Search found 104 matches

by Rebecca Remple 1C
Wed Feb 19, 2020 1:39 pm
Forum: Administrative Questions and Class Announcements
Topic: Dr. Lavelle's Office Hours
Replies: 1
Views: 12

Dr. Lavelle's Office Hours

Hi all, I was wondering if Dr. Lavelle has Office Hours for this course and, if so, where and when they are? I know he had Office Hours last quarter in 14A, and I would like to meet with him before the end of the quarter to discuss the class. If anyone has information on this matter, please let me k...
by Rebecca Remple 1C
Wed Feb 19, 2020 1:36 pm
Forum: Balancing Redox Reactions
Topic: Test 2 [ENDORSED]
Replies: 12
Views: 70

Re: Test 2 [ENDORSED]

Aiden Metzner 2C wrote:Is test 2 next week? And if so what subject areas is it covering?

Hi Aiden,

Dr. Lavelle moved Test 2 to week nine. It will cover outlines 4 and 5. Hope this helps!

-Rebecca
by Rebecca Remple 1C
Sun Feb 16, 2020 5:47 pm
Forum: Administrative Questions and Class Announcements
Topic: Video Outlines
Replies: 3
Views: 14

Re: Video Outlines

Omar Selim 1D wrote:Are there video outlines for any of the recent topics?

Hi Omar,

I haven't seen any posted. Maybe he will upload some later if there is student demand for them!

Best,
Rebecca
by Rebecca Remple 1C
Sun Feb 16, 2020 5:45 pm
Forum: Administrative Questions and Class Announcements
Topic: Extra Credit
Replies: 7
Views: 49

Re: Extra Credit

I missed 5 points for the chemistry community. Will there be extra points in the class? Hi there, Unfortunately, there is no extra offered in this course. Dr. Lavelle has stated that he will adjust grades after all points are entered (meaning after the final) if necessary, although there is not a &...
by Rebecca Remple 1C
Sun Feb 16, 2020 5:43 pm
Forum: Administrative Questions and Class Announcements
Topic: when are your #of posts on CC collected each week?
Replies: 4
Views: 26

Re: when are your #of posts on CC collected each week?

Sue Bin Park 2I wrote:do the TAs collect them on mondays? fridays?

Hi Sue,

I agree with the users above me. The cutoff is Sunday night at 11:59 PM unless Dr. Lavelle states otherwise. I hope this helps!

Best,
Rebecca
by Rebecca Remple 1C
Wed Feb 12, 2020 5:12 pm
Forum: Calculating Work of Expansion
Topic: Pizza Rolls #6
Replies: 1
Views: 31

Re: Pizza Rolls #6

"You have a system consisting of 0.40 moles of an ideal gas contained in a 100.0L container at 1.0 atm. You just love chemistry to a fault, so you perform a series of steps to the system. First, you perform an isobaric compression of the container to 10.0L. Then, you pressurize the system to 1...
by Rebecca Remple 1C
Wed Feb 12, 2020 2:06 pm
Forum: Phase Changes & Related Calculations
Topic: Rotational/Translational Contributions?
Replies: 2
Views: 34

Re: Rotational/Translational Contributions?

The values given indicate what the heat capacity of an ideal gas could be at constant volume and constant pressure. the main concept to know here is that the change in internal energy = (3/2)Rdelta T. You can find the heat capacity by dividing delta U by delta T. You can use the "How Do We Kno...
by Rebecca Remple 1C
Mon Feb 10, 2020 5:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sign of Energy Density
Replies: 2
Views: 20

Re: Sign of Energy Density

I think energy density is always positive, since the definition of energy density is "the amount of energy stored in a given system or region of space per unit volume." I don't think energy can be negative (but I may be wrong), so energy density can't be negative. Hi Alice, Thank you so m...
by Rebecca Remple 1C
Mon Feb 10, 2020 4:59 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Double Greater than Sign
Replies: 2
Views: 10

Double Greater than Sign

Hi all, In an example we did in class, Dr. Lavelle wrote "S G >> S L > S s ". I was wondering what the double greater than sign, >>, means in this context. Why is the difference between gas and liquid different from the difference between liquid and solid? Please let me know. Thank you! -R...
by Rebecca Remple 1C
Sun Feb 09, 2020 6:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sign of Energy Density
Replies: 2
Views: 20

Sign of Energy Density

Hi all, In homework problem 4D.9 we are asked to calculate the energy density of a reaction. I found the enthalpy, which was negative. This meant that energy/heat was being released. However, according to the solutions manual, the sign changed to positive when calculating the energy density of the r...
by Rebecca Remple 1C
Sun Feb 09, 2020 5:56 pm
Forum: Phase Changes & Related Calculations
Topic: Rotational/Translational Contributions?
Replies: 2
Views: 34

Rotational/Translational Contributions?

Hi all, I am struggling to understand what is meant by rotational and translational contributions. Homework problem 4C.5 deals with these contributions of molecular motions. I understand how to add the two contributions together but do not understand the question conceptually. What do these contribu...
by Rebecca Remple 1C
Sun Feb 09, 2020 5:47 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.23
Replies: 2
Views: 23

Re: 4D.23

Calculate the standard enthalpy of formation of dinitrogen pentoxide from the following data: 2 NO(g) + O2(g) --> 2 NO2(g); delta H° = -114.1 kJ 4 NO2(g) + O2(g) --> 2 N2O5(g); delta H° = -110.2 kJ and from the standard enthalpy of formation of nitric oxide, NO (see Appendix 2A). how do i calculate...
by Rebecca Remple 1C
Sun Feb 09, 2020 5:40 pm
Forum: Phase Changes & Related Calculations
Topic: 4.23
Replies: 1
Views: 18

Re: 4.23

in this problem, we have to use the equation E = hc/λ and calculate the number of photons needed for the rxn will we have to know this and other quantum equations for the midterm? Hi there, From what I understand, we only have to know equations from Dr. Lavelle's Constants and Equations sheet: http...
by Rebecca Remple 1C
Sun Feb 09, 2020 5:36 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Learning outcome fossil fuels
Replies: 2
Views: 29

Re: Learning outcome fossil fuels

On the learning outcomes sheet for "Thermochemistry and the First Law of Thermodynamics" from Dr. Lavelle's class website, it says we should "understand the environmental impact of burning fossil fuels, and the use of alternative fuels as energy sources." Can someone explain how...
by Rebecca Remple 1C
Sat Feb 01, 2020 3:59 pm
Forum: Administrative Questions and Class Announcements
Topic: 14A final solutions
Replies: 6
Views: 59

Re: 14A final solutions

Hi there, I've not seen the solutions posted anywhere, but you can pick up your midterm at 3034 Young Hall! They have them fully graded, so you can see what you missed. You can read more about the process here: https://lavelle.chem.ucla.edu/forum/viewtopic.php?p=214489&sid=8da1e337f667784da8b244...
by Rebecca Remple 1C
Sat Feb 01, 2020 3:58 pm
Forum: Administrative Questions and Class Announcements
Topic: 14A Final Answer Key
Replies: 5
Views: 50

Re: 14A Final Answer Key

Hi Annie, I do not know if the answer key is available, but you can actually pick up your midterm at 3034 Young Hall! They have them fully graded and with many of the correct answers filled in. You can read the thread about it here: https://lavelle.chem.ucla.edu/forum/viewtopic.php?p=214489&sid=...
by Rebecca Remple 1C
Sat Feb 01, 2020 3:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Water and Equilibrium
Replies: 2
Views: 13

Water and Equilibrium

Hi all, I had a question regarding one of the problems in Test #1. In this problem, gaseous H2O effected the equilibrium constant of the system. I was confused by this, because I regarded all forms of water as a pure substance that would not be factored into equilibrium calculations. Does the state ...
by Rebecca Remple 1C
Sat Feb 01, 2020 3:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Material
Replies: 13
Views: 64

Re: Midterm Material

Hi there, You can find all of the information regarding the midterm here: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Midterm_Review_Sessions_14B.pdf If you have any trouble with the link, it's located under "Midterm Exam: Review Sessions and Exam Venues" on the 14B c...
by Rebecca Remple 1C
Sat Feb 01, 2020 3:48 pm
Forum: Administrative Questions and Class Announcements
Topic: Fall Quarter Final?
Replies: 12
Views: 74

Re: Fall Quarter Final?

Hi all, Thanks for your replies! I wanted to update everyone about the situation. They are still passing back fall quarter finals from 14A in Young 3034! If you walk into Young Hall, there is a large glass window through which you can speak with staff in the room. You need to give them your Bruincar...
by Rebecca Remple 1C
Sun Jan 26, 2020 3:45 pm
Forum: Administrative Questions and Class Announcements
Topic: Fall Quarter Final?
Replies: 12
Views: 74

Fall Quarter Final?

Hi all, I heard earlier that the Fall quarter final would be available in Young 3034 during week 3. However, I assumed that Dr. Lavelle would send out an email with the times we could come to pick up the exam. I never received instructions about when and how to pick it up. Does anyone know if the ex...
by Rebecca Remple 1C
Mon Jan 20, 2020 7:17 pm
Forum: Student Social/Study Group
Topic: Test 1
Replies: 9
Views: 61

Re: Test 1

are there any past exams to help us study for test 1? does the professor usually post a practice test beforehand? Hi Dina, There is no practice test, but he will pull questions from the assigned homework! I would recommend going through those problems to get a better understanding of the test's con...
by Rebecca Remple 1C
Mon Jan 20, 2020 7:15 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: When to ignore the second (de)protonization?
Replies: 5
Views: 27

Re: When to ignore the second (de)protonization?

I think that you would ignore it if the second deprotonization or third (etc.) does not affect the pH of the solution. In the textbook, it says that for most polyphonic acid, the 2nd or more Ka is so small that pH of the solution isn't really affected. However, for H2SO4, this is an exception where...
by Rebecca Remple 1C
Mon Jan 20, 2020 7:13 pm
Forum: Student Social/Study Group
Topic: Any Worksheets from UA/TA/etc?
Replies: 14
Views: 152

Re: Any Worksheets from UA/TA/etc?

Does anyone know if there are any practice worksheets from UAs, TAs, etc for Chem 14B? I remember for Chem 14A last quarter, some UAs had worksheets posted on here so I'm just wondering if there is any for this course. Hi Jasmine, I hear that some UAs and TAs do worksheets, while others do not. My ...
by Rebecca Remple 1C
Mon Jan 20, 2020 7:05 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: When to ignore the second (de)protonization?
Replies: 5
Views: 27

When to ignore the second (de)protonization?

Hi all, Both homework problems from section 6E ask about the second deprotonization. However, while the second (de)protonization is used to calculate pH in problem 6E.1, it is ignored in the problems in 6E.3. I was wondering if someone can explain why this is. At what point does the second (de)proto...
by Rebecca Remple 1C
Sat Jan 18, 2020 4:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pKa versus pH
Replies: 3
Views: 31

Re: pKa versus pH

I understand the difference between pKa and pH in terms of the formula, but I don't really understand how they differ conceptually. Adding to this, I don't understand why when pKa > pH, it's acidic and when pKa < pH, it's basic. Does it have something to do with the conjugate base? It has to be rig...
by Rebecca Remple 1C
Sat Jan 18, 2020 4:11 pm
Forum: Administrative Questions and Class Announcements
Topic: UA Sessions
Replies: 2
Views: 17

Re: UA Sessions

Will there be UA sessions this Monday? Hi Ayushi, I had the same question! Unfortunately, I was told that there most likely will not because Office Hours and classes are not occurring on that day. If I hear anything else to the contrary, I will be sure to let you know! Good luck on the test :) -Reb...
by Rebecca Remple 1C
Sat Jan 18, 2020 4:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Getting Back 14A Final Exam
Replies: 3
Views: 25

Re: Getting Back 14A Final Exam

Someone said they went to the room to check and they said by Week 3. I don't think it'd be possible to get your test prior to your test a day or so in advance. If anything, I'd suggest going to pick it up an hour or so before your test if they're open. Good luck! Hi Megan, Thank you for letting me ...
by Rebecca Remple 1C
Sat Jan 18, 2020 2:57 pm
Forum: Ideal Gases
Topic: Solids and Liquids [ENDORSED]
Replies: 10
Views: 65

Re: Solids and Liquids [ENDORSED]

I agree with Fiona and McKenna! However, I am still confused on the matter of liquids being pure substancews. Can someone clarify how a liquid is different from an aqueous solution and give examples of each? From what I understand, aqueous solutions have a solute and solvent, and liquids do not. Ca...
by Rebecca Remple 1C
Sat Jan 18, 2020 2:55 pm
Forum: Administrative Questions and Class Announcements
Topic: Learning Sessions on Monday?
Replies: 2
Views: 12

Learning Sessions on Monday?

Hi all, I was wondering if there will be any UA-led study sessions during the Monday holiday? I was assuming not because it is a day off for all students, but I wasn't sure if some UAs might be hosting them anyways. I'm especially interested in Step-Up or Workshop sessions. Please let me know your t...
by Rebecca Remple 1C
Sat Jan 18, 2020 2:52 pm
Forum: Administrative Questions and Class Announcements
Topic: Getting Back 14A Final Exam
Replies: 3
Views: 25

Getting Back 14A Final Exam

Hi all, I hope you're doing well! I was wondering when we will be able to get back the Chemistry 14A final exam from Dr. Lavelle's classes last quarter. I was informed that they will be given back during Week 3 of this quarter. I was hoping to review my old final before Test 1 so I can better unders...
by Rebecca Remple 1C
Sat Jan 11, 2020 3:19 pm
Forum: Ideal Gases
Topic: Law of Effusion, Kinetic Model, and Maxwell Distribution
Replies: 3
Views: 33

Re: Law of Effusion, Kinetic Model, and Maxwell Distribution

Focus 3D covers Graham's Law of Effusion, the Kinetic Model of Gases, and the Maxwell Distribution of Speeds. Do you think we will need to know these concepts in depth, and can anyone give a short summary of these, if possible? Thanks! Hi Ariel, The syllabus doesn't list these concepts, so I doubt ...
by Rebecca Remple 1C
Sat Jan 11, 2020 3:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Required number of responses for chem community
Replies: 7
Views: 35

Re: Required number of responses for chem community

Tyler Angtuaco 1G wrote:Is the required number of responses for Chemistry Community still 5 responses for Chem14B?

Hi Tyler,

The requirement is still 5 posts per week, as well as the 5 homework problems that are due every discussion. There are 50 points total for the whole quarter. I hope this helps!

-Rebecca
by Rebecca Remple 1C
Sat Jan 11, 2020 3:12 pm
Forum: Ideal Gases
Topic: Solids and Liquids [ENDORSED]
Replies: 10
Views: 65

Re: Solids and Liquids [ENDORSED]

I agree with Fiona and McKenna! However, I am still confused on the matter of liquids being pure substancews. Can someone clarify how a liquid is different from an aqueous solution and give examples of each? From what I understand, aqueous solutions have a solute and solvent, and liquids do not. Can...
by Rebecca Remple 1C
Sat Jan 11, 2020 3:06 pm
Forum: Ideal Gases
Topic: K vs Q [ENDORSED]
Replies: 7
Views: 44

Re: K vs Q [ENDORSED]

I have a question about when to use K and Q. Also, what's the main difference between the two. Thank you. :) Hi Donavin, From what I understand, K is the equilibrium constant while Q is the reaction quotient. K is calculated using the concentrations of reactants and products at equilibrium. Q is no...
by Rebecca Remple 1C
Sat Jan 11, 2020 3:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressure
Replies: 7
Views: 23

Re: Partial Pressure

Donavin Collins 1F wrote:I need a bit of clarification for partial pressure. Is it only used for gases?

Hi Donavin,

From what I understand partial pressures are only used for gases :) This is true for all of the practice problems that include gases as reactants or products. I hope this helps!

-Rebecca
by Rebecca Remple 1C
Sun Dec 08, 2019 9:12 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strong vs. Weak Acids
Replies: 3
Views: 41

Re: Strong vs. Weak Acids

Hi, HOI and HOCl are oxoacids. Look at stability of conjugate base ClO-. The conjugate base is more stable when the electron density is distributed over more atoms versus concentrated on the oxygen only. Cl is more electronegative than I, so it can withdraw more electron density from the Oxygen. Th...
by Rebecca Remple 1C
Sun Dec 08, 2019 9:10 am
Forum: Identifying Acidic & Basic Salts
Topic: Mini Marshmallows 1C - Acidic Salt?
Replies: 2
Views: 39

Re: Mini Marshmallows 1C - Acidic Salt?

NO3- participates in the reaction, but it does not change the acidity of the solution, and therefore does not affect the pH, so we can disregard it when considering pH levels. This is because NO3- is the conjugate base of HNO3, which is a strong acid and the conjugate bases of strong acids do not a...
by Rebecca Remple 1C
Sat Dec 07, 2019 8:13 pm
Forum: Identifying Acidic & Basic Salts
Topic: Mini Marshmallows 1C - Acidic Salt?
Replies: 2
Views: 39

Mini Marshmallows 1C - Acidic Salt?

Hey again,

In Mini Marshmallows 1C, why does the NO3- in NH4NO3 not participate in the reaction with water, but NH4+ does? I just want to make sure I understand this conceptually before the final. Thank you!

-Rebecca
by Rebecca Remple 1C
Sat Dec 07, 2019 8:11 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4121

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Hey again,

In Mini Marshmallows 1C, why does the NO3- in NH4NO3 not participate in the reaction with water, but NH4+ does? I just want to make sure I understand this conceptually before the final. Thank you!

-Rebecca
by Rebecca Remple 1C
Sat Dec 07, 2019 7:15 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4121

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Can someone explain how to get the pH for 34. I got the moles of each compound but can’t seem to get the overall pH. Hi Jonathan, Using the moles for CaO and HCl, you can determine how many moles of OH- and H+ are produced. You need to write out the equations in water to do so. Note that 2 moles of...
by Rebecca Remple 1C
Sat Dec 07, 2019 7:10 pm
Forum: Air Pollution & Acid Rain
Topic: What do we need to know?
Replies: 4
Views: 70

Re: What do we need to know?

does anyone know if its going to be more focused on material after the mid-term or is it just going to be random? Hi there, I heard that the questions will be pretty evenly distributed, so a good portion of the final will cover topics from the midterm as well as from after it. I hope this helps! Go...
by Rebecca Remple 1C
Sat Dec 07, 2019 7:09 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strong vs. Weak Acids
Replies: 3
Views: 41

Strong vs. Weak Acids

Hi all, I'm preparing for the final by reviewing the rules for strong and weak acids. I understand that bond length in HF and HI makes HI a stronger acid, because it is more likely to lose a proton. However, why is HOCl stronger than HOI? I read through the explanation in the review worksheet, but I...
by Rebecca Remple 1C
Sat Dec 07, 2019 7:03 pm
Forum: Hybridization
Topic: Marshmallows #17 - hybridization in pi bonds
Replies: 2
Views: 34

Re: Marshmallows #17 - hybridization in pi bonds

My guess is that it's a typo. Pi bonds result from the overlapping of p orbitals specifically (think of it like two infinity symbols, one on top of the other) so the pi bond should only have p character. Hi Aadil, Thank you so much for replying! I'm glad to know I'm not the only one who thought tha...
by Rebecca Remple 1C
Sat Dec 07, 2019 6:19 pm
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4121

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Hi all, I was going through the final review packet and have been having trouble understanding part of problem 17. In the problem, it asks us to draw C5H5NO2 and label all of the sigma and pi bonds. I understand most of the question, but one of the pi bonds is troubling me. Near the top of the molec...
by Rebecca Remple 1C
Sat Dec 07, 2019 6:17 pm
Forum: Hybridization
Topic: Marshmallows #17 - hybridization in pi bonds
Replies: 2
Views: 34

Marshmallows #17 - hybridization in pi bonds

Hi all, I was going through Lyndon's final review packet and have been having trouble understanding part of problem 17. In the problem, it asks us to draw C5H5NO2 and label all of the sigma and pi bonds. I understand most of the question, but one of the pi bonds is troubling me. Near the top of the ...
by Rebecca Remple 1C
Sat Dec 07, 2019 9:58 am
Forum: Administrative Questions and Class Announcements
Topic: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]
Replies: 111
Views: 4121

Re: MARSHMALLOW- FINAL REVIEW SESSION [ENDORSED]

Hi there! Thank you so much for sharing these practice problems. I was wondering if the answer key to the regular worksheet will be posted soon? I was not able to make the session but have been working on the problems, so I would love to be able to refer to it. Thank you!
by Rebecca Remple 1C
Thu Nov 28, 2019 4:28 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Final Exam
Replies: 10
Views: 85

Re: Final Exam

I wasn't sure which section to put this under, but will the final exam include all the content we have covered including the fundamentals? Thank you. Hi there, The final will be cumulative, although recent material will probably make up the majority of it. You can expect to see questions that combi...
by Rebecca Remple 1C
Thu Nov 28, 2019 4:26 pm
Forum: Naming
Topic: Oxidation
Replies: 14
Views: 107

Re: Oxidation

Also can anyone explain what oxidation is? And what Dr. Lavelle meant by oxidation states? I don't remember him explaining the concept in class. Hi Kennedi, I agree with the other commenters about oxidation states and numbers. To answer your first questions, an oxidation reaction represents the los...
by Rebecca Remple 1C
Thu Nov 28, 2019 4:22 pm
Forum: Bronsted Acids & Bases
Topic: Writing Equations
Replies: 1
Views: 21

Re: Writing Equations

How do you know when to write an equation with the arrow pointing one way versus the set of arrows pointing both ways? Hi there, I talked to my TA about this and, apparently, many chemical equations can be written either way. Most acid-base reactions are "irreversible" because the backwar...
by Rebecca Remple 1C
Thu Nov 28, 2019 4:18 pm
Forum: Hybridization
Topic: single vs double vs triple bonds
Replies: 4
Views: 28

Re: single vs double vs triple bonds

Why doesn't the number of bonds affect which hybrid orbital is formed? For instance, in ethylene c2h4, why is the double bond in between the carbons just two sp^2 hybrid orbitals instead of two individual sp^3 orbitals (since there are four bonds formed by carbon in total)? Hi Chris, I agree with t...
by Rebecca Remple 1C
Thu Nov 28, 2019 4:15 pm
Forum: Bronsted Acids & Bases
Topic: Writing Equations
Replies: 1
Views: 19

Re: Writing Equations

When you're writing out the equations for acid-base reactions, how do you know whether the molecules (for both products and reactants) will be an aqueous solution or a liquid if the question doesn't specify? Hi Labiba, This is confusing to me too! However I have found that, in general, products nor...
by Rebecca Remple 1C
Thu Nov 21, 2019 7:05 pm
Forum: Sigma & Pi Bonds
Topic: sigma and pi bonds
Replies: 3
Views: 24

Re: sigma and pi bonds

If you see a single bond, it will be a sigma bond. Pi bonds occur whenever there's a p-orbital interacting with another p-orbital, so when there's a double bond, one will be a pi bond and the other will be a sigma bond (because if you have 2 pi bonds the bond will break). so every bond ever? in pol...
by Rebecca Remple 1C
Thu Nov 21, 2019 7:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles for trigonal bipyramidal and octahedral
Replies: 2
Views: 31

Re: Bond angles for trigonal bipyramidal and octahedral

What are the bond angles for Trigonal Bipyramidal and octahedral arrangements when they have one and two lone pairs? i.e. bond angles for seesaw, t shaped, square pyramidal and square planar? Hi there, I agree with the previous answer! If you have any trouble visualizing this, I have attached a stu...
by Rebecca Remple 1C
Thu Nov 21, 2019 6:56 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: in need of test 2 practice problems
Replies: 5
Views: 65

Re: in need of test 2 practice problems

hello! does anyone have practice problems for test 2? from any UA sessions or anything? please copy here (or email/text me) Hi there, I would recommend revisiting the homework problems in section 2E of the textbook. Also, if you have difficulty visualizing 3D molecular structures, I would recommend...
by Rebecca Remple 1C
Thu Nov 21, 2019 6:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 2
Replies: 14
Views: 110

Re: Test 2

Does anyone have any advice for remembering molecular shape? Hi Cassandra, I think it's good to start by remembering molecular geometry, where lone pairs are counted as regions of electron density. If there are 2 areas of electron density, the shape is linear and the angle 180 degrees. If there are...
by Rebecca Remple 1C
Wed Nov 20, 2019 3:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape vs. Geometry
Replies: 5
Views: 39

Molecular Shape vs. Geometry

Hey all, I hope you're doing well! Can someone please explain the difference between molecular shape and geometry? I am having a difficult time understanding which is which, as the different resources I am using have varied definitions. If possible, can you provide examples for both? Thank you in ad...
by Rebecca Remple 1C
Wed Nov 13, 2019 3:22 pm
Forum: *Particle in a Box
Topic: Principle quantum number
Replies: 2
Views: 30

Re: Principle quantum number

Hi Clara, If you are given enough information, you can do this using the Rydberg formula. You can find this formula on the constants and equations sheets. This will work if you known one of the principle quantum numbers (e.g. at ground state, Hydrogen's principle quantum number = 1). You can then pl...
by Rebecca Remple 1C
Wed Nov 13, 2019 3:19 pm
Forum: DeBroglie Equation
Topic: Use
Replies: 2
Views: 36

Re: Use

Hi Clara! You can use it if you need to find wavelength and are given values for mass and/or speed of an object. It can be used for large objects, like baseballs, which cannot be plugged into the light-specific equations like c=wavelength*frequency. If you aren't given a mass, you can find masses fo...
by Rebecca Remple 1C
Wed Nov 13, 2019 3:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Answers
Replies: 10
Views: 106

Re: Midterm Answers

Here's the link: https://lavelle.chem.ucla.edu/wp-conten ... rm_ans.pdf
If the link doesn't work, you can find it on his Chemistry 14A class website under "Exam Information" :) I hope this helps!
by Rebecca Remple 1C
Wed Nov 13, 2019 3:14 pm
Forum: Administrative Questions and Class Announcements
Topic: Regrade requests
Replies: 3
Views: 72

Re: Regrade requests

You can email your TA, or speak to them during Office Hours or Discussion. I hope this helps!
by Rebecca Remple 1C
Wed Nov 13, 2019 3:13 pm
Forum: Administrative Questions and Class Announcements
Topic: Class grading
Replies: 12
Views: 199

Re: Class grading

Hi Tyler! I agree with all the previous replies. Additionally, there's a chance (but no guarantee) that Dr. Lavelle may curve grades if the class average is low. From what I hear, he would only curve up, meaning that it would raise your final grade. However, if the class average is above or at his e...
by Rebecca Remple 1C
Wed Nov 13, 2019 3:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm grade
Replies: 4
Views: 49

Re: Midterm grade

Hi Savannah! We got our physical midterms back in my class. If you weren't able to get yours, you can email your TA or go to their Office Hours. I heard that scores were supposed to be posted to CCLE today, but they were delayed. If you can't get the midterm back physically, I'm sure they will be up...
by Rebecca Remple 1C
Wed Nov 13, 2019 3:08 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground state?
Replies: 6
Views: 64

Ground state?

Hi all, I hope you're all doing well! I'm a bit confused about the meaning of the term "ground state". In the test, one question asked about a "ground state ion". I originally thought that being in a ground state means that an atom has no charge. However, since ions are charged, ...
by Rebecca Remple 1C
Fri Nov 08, 2019 2:37 pm
Forum: Administrative Questions and Class Announcements
Topic: Discussion-Week 9
Replies: 3
Views: 42

Re: Discussion-Week 9

Hello! I was wondering if anyone knows whether or not we will have discussion sections week 9. This is the week of Thanksgiving so I am trying to plan when to go home. They won't have discussion during the day offs for Thanksgiving break (Thursday and Friday). However, if you have discussion Monday...
by Rebecca Remple 1C
Fri Nov 08, 2019 2:35 pm
Forum: Lewis Structures
Topic: Midterm grades
Replies: 26
Views: 249

Re: Midterm grades

Does anyone know when midterm grades will be released? I'm assuming that we'll get them back week 7. Dr. Lavelle shared in class that the average score was 75%, which implies that they've been mostly graded. However, I'm sure they still have work to do in terms of finalizing the grades, assigning p...
by Rebecca Remple 1C
Fri Nov 08, 2019 2:32 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Monday Lecture
Replies: 2
Views: 34

Re: Monday Lecture

Since we don't have school on Monday, is there anything we need to prepare for the Friday lecture or no? There's no lecture on Monday, and Dr. Lavelle didn't mention any extra work you need to do in its place. I'm assuming there won't be any extra preparation/assignments required. Just the usual Ch...
by Rebecca Remple 1C
Fri Nov 08, 2019 2:30 pm
Forum: Trends in The Periodic Table
Topic: Atomic Radii
Replies: 10
Views: 69

Re: Atomic Radii

Why does atomic radii decrease even though the number of protons increase as you go across a period? I agree with the previous responses! I wanted to add that, in general, electrons repel each other and are attracted to protons. Having more protons in the nucleus, and thus a higher/more positive ch...
by Rebecca Remple 1C
Tue Nov 05, 2019 9:13 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shape of Orbitals?
Replies: 3
Views: 55

Shape of Orbitals?

Hi all, I was going through my notes for class and noticed that, during the Quantum World unit, we covered the different shapes of orbitals. The s orbitals are spherical, the p are two lobes, d has several lobes (3 or 4?), and f has more complicated shapes. However, I never encountered any practice ...
by Rebecca Remple 1C
Sat Nov 02, 2019 4:46 pm
Forum: Ionic & Covalent Bonds
Topic: "Primarily Ionic" Bonds (HW 2D.3)
Replies: 2
Views: 43

"Primarily Ionic" Bonds (HW 2D.3)

Hi all, I hope you're all doing well! I have a question regarding the homework problem 2D.3. This problem asks "Which of these compounds has bonds that are primarily ionic? a) BBr 3 b) BaBr 2 c) BeBr 2 ." The correct answer is BaBr 2 because it has the greatest electronegativity difference...
by Rebecca Remple 1C
Sat Nov 02, 2019 4:40 pm
Forum: Resonance Structures
Topic: Resonance structure
Replies: 4
Views: 33

Re: Resonance structure

Can someone explain to me how to even get the resonance structure from a lewis structure? for example, NH4+, what is it supposed to look like? Hi Doris, I'm honestly not sure what NH4+'s resonance structures would look like, as Hydrogen has a +1 charge and cannot form any double/triple bonds. Howev...
by Rebecca Remple 1C
Sat Nov 02, 2019 3:08 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: f-orbitals
Replies: 2
Views: 27

Re: f-orbitals

The f orbital is rarely used because it deals with radioactive elements, which are elements that are rarely used in the type of bonding we are doing. I don't believe we will need to know how to do problems with the f orbital. The f orbital comes into play when you get to these higher elements in th...
by Rebecca Remple 1C
Mon Oct 28, 2019 3:57 pm
Forum: Ionic & Covalent Bonds
Topic: Number of Chemistry Community Posts
Replies: 3
Views: 48

Re: Number of Chemistry Community Posts

As on last night you should have posted 20 times I think because we just finished week 4. Yes, this would be correct! After this week, you should have brought it up to 25. I'm not sure if Dr. Lavelle keeps track of posts every week, or if he bases our score on the total number of posts we've made o...
by Rebecca Remple 1C
Mon Oct 28, 2019 3:52 pm
Forum: Administrative Questions and Class Announcements
Topic: 10/28 Updates due to Fire [ENDORSED]
Replies: 14
Views: 864

Re: 10/28 Updates due to Fire [ENDORSED]

Is the midterm review session at 6 today also cancelled? Thank you! I am not sure what review session you are referring to! Hi there, Thank you so much for the update! I was wondering if fire will effect the other review sessions this week? Also, is there a schedule for midterm review sessions yet ...
by Rebecca Remple 1C
Mon Oct 28, 2019 3:49 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Hund's Rule
Replies: 2
Views: 24

Re: Hund's Rule

also, is there an example that can clearly show the usage of hund's rule? Hi Salma! :) I hope you're doing well! Hund's rule basically states that ever orbital must be singly occupied before they can be doubly occupied. This can be represented in an Aufbau diagram (the diagram where each orbital is...
by Rebecca Remple 1C
Mon Oct 28, 2019 3:30 pm
Forum: Administrative Questions and Class Announcements
Topic: 10/28 Updates due to Fire [ENDORSED]
Replies: 14
Views: 864

Re: 10/28 Updates due to Fire [ENDORSED]

Hi there,

Thank you so much for the update! I was wondering if fire will effect the other review sessions this week? Also, is there a schedule for midterm review sessions yet and, if so, where can we access it? Thank you again and I hope you have a great day!

-Rebecca
by Rebecca Remple 1C
Mon Oct 28, 2019 3:26 pm
Forum: Resonance Structures
Topic: HW Question 2B9
Replies: 3
Views: 26

Re: HW Question 2B9

2B9. Draw the complete Lewis structure for each of the following compounds: (a) ammonium chloride; (b) potassium phosphide; (c) sodium hypochlorite How come for these structures you draw the elements separately? For example in part b, the answer key shows K+ around a P -3 instead of lines connectin...
by Rebecca Remple 1C
Mon Oct 28, 2019 3:19 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: f-orbitals
Replies: 2
Views: 27

f-orbitals

Hi all, I hope everyone is doing well and staying safe from the fires! I had a clarification question regarding the f-orbital. In class and discussion, we rarely (if ever) deal with this orbital, and it's usually omitted from the homework as well. However, I encountered it while working on some of t...
by Rebecca Remple 1C
Tue Oct 22, 2019 3:48 pm
Forum: Properties of Light
Topic: Homework due Next Week
Replies: 9
Views: 80

Re: Homework due Next Week

Is this the last homework we will turn in under the quantum unit? Hi Maya, Since Dr. Lavelle wrapped up the Quantum World unit yesterday, I assume we are transitioning into Chemical Bonds next. If this is true, we will probably be doing problems from the new section for next week. I'm currently uns...
by Rebecca Remple 1C
Tue Oct 22, 2019 3:38 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Excited state vs ground state
Replies: 4
Views: 29

Re: Excited state vs ground state

When an electron is excited, it can jump from one orbital to another. It will usually jump to a higher energy orbital. For example, if an atom's electron configuration is 1s 2 2s 2 2p 6 , its excited configuration could be 1s 2 2s 1 2p 6 3s 1 . This means that one electron, which was originally in t...
by Rebecca Remple 1C
Tue Oct 22, 2019 3:32 pm
Forum: General Science Questions
Topic: Units
Replies: 4
Views: 41

Re: Units

Velocity: meters per second Threshold energy: Joules Plank's constant: Joules times seconds Frequency: Hz (which is also cycles per second) You can also find these on the constants and equations sheet that they give us during tests: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/...
by Rebecca Remple 1C
Tue Oct 22, 2019 3:27 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Knowing the nm of light
Replies: 2
Views: 29

Re: Knowing the nm of light

I remember my TA saying something about knowing the general range for visible light and UV radiation. Even this doesn't need to be too specific. 400-700nm is the visible spectrum, which might be a good thing to memorize so you can gauge the general range for the other wavelengths. Overall, I wouldn...
by Rebecca Remple 1C
Tue Oct 22, 2019 3:24 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Hw Help 1D.25
Replies: 3
Views: 30

Re: Hw Help 1D.25

Hi Bita, Both B and D can exist, but A and C cannot. A cannot exist because there is no 2d subshell. Instead, the lowest "d" subshell is 3d. The subshells preceding 3d are (from lowest to highest energy) 1s, 2s, 2p, 3s, 3p, and 4s. C cannot exist because the lowest "g" subshell i...
by Rebecca Remple 1C
Thu Oct 17, 2019 8:36 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: n, l, and m notation
Replies: 2
Views: 31

Re: n, l, and m notation

the subscript on m is not a 1, it is an l. m(sub l) is the magnetic quantum number which indicates the orientation of the shell (where l indicates shape) so l=2 tells you it's a d-orbital and m(sub l)=+1 tells you it is d(sub yz) orientation (or it could be a different orientation based on if they ...
by Rebecca Remple 1C
Thu Oct 17, 2019 5:38 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7834
Views: 1088498

Re: Post All Chemistry Jokes Here

This is definitely the best type of Chemistry Lab :)
chem lab.jpg
by Rebecca Remple 1C
Thu Oct 17, 2019 5:33 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW Help
Replies: 3
Views: 32

Re: HW Help

Hi Nikki,

I also wrote the total number of orbitals. I reported them the same as Manav, which is also how they're written in the Student Answers Manual! But it's a good idea to write out the possibilities, then total them up. I hope this helps!

-Rebecca
by Rebecca Remple 1C
Thu Oct 17, 2019 5:27 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation Alternatives?
Replies: 4
Views: 45

Re: Rydberg Equation Alternatives?

Hi Rodrigo and Simon, Thank you so much for your replies! I really appreciate the help. Would either of you be willing to show how you solved this homework problem? From what I've seen, I have to use a specific form of the Rhydberg equation, but I'm confused by the way the textbook solved it and I f...
by Rebecca Remple 1C
Thu Oct 17, 2019 5:23 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: n, l, and m notation
Replies: 2
Views: 31

n, l, and m notation

Hi all, I have a question regarding the notation for n, l, and m. In homework question 1.23 part d, n=3, l=2, and m 1 =+1. The first two are pretty clear. However, I'm not sure what to do with the value of m 1 . Since l=2, I'd assume we're using m 2 . Therefore, I don't know how m 1 fits in and effe...
by Rebecca Remple 1C
Thu Oct 17, 2019 5:20 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 1D.23
Replies: 2
Views: 30

Re: 1D.23

Hi, I attached a chart that you can use for reference! I used it alongside the info Lavelle gave us, and it really helped me contextualize the information better. In part a, since n=2 and l=1, there are 3 possible orbitals depending on m's value (ml= l, l-1, ... -l). Therefore, m can be either 1, 0,...
by Rebecca Remple 1C
Thu Oct 17, 2019 5:04 pm
Forum: Properties of Electrons
Topic: Angstrom Conversion
Replies: 12
Views: 103

Re: Angstrom Conversion

Hi Kallista, I agree with all of the previous responses, especially with Norman's advice. If you have any trouble remembering the specific conversions (e.g. picometers, nanometers, etc.) I wanted to let you know that they're all in Dr. Lavelle's "Constants and Equations" sheet! Don't worry...
by Rebecca Remple 1C
Sat Oct 12, 2019 5:09 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation Alternatives?
Replies: 4
Views: 45

Rydberg Equation Alternatives?

Hi all, I'm currently working on the homework from section 1A when I came across an interesting problem, 1A.15. The problem states that "In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the elect...
by Rebecca Remple 1C
Sat Oct 12, 2019 4:54 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Test 1 [ENDORSED]
Replies: 107
Views: 2851

Re: Test 1 [ENDORSED]

ahuang wrote:Does anyone know when we will be receiving our tests back?


I'm not 100% sure because every TA has a different schedule, but I heard they should all be graded by the end of next week! It seems like some TAs are planning to have them done by the next sections, so I feel like that's a good guess.
by Rebecca Remple 1C
Sat Oct 12, 2019 3:06 pm
Forum: Limiting Reactant Calculations
Topic: percent yield
Replies: 10
Views: 159

Re: percent yield

Hi Bella, I agree with the previous posters that you do not have to show percent yield on limiting reactant problems. In fact, the yield you calculate using the limiting reactant would actually be the theoretical/maximum yield! Basically, the limiting reactant determines the maximum amount of produc...
by Rebecca Remple 1C
Sat Oct 12, 2019 2:59 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Test 1 [ENDORSED]
Replies: 107
Views: 2851

Re: Test 1 [ENDORSED]

Can someone explain what Angstroms are? I was confused on the test on this question. That one confused me too! However, I realized that the conversions were on the front of the test on the resource page. 1 Angstrom is 10 -10 m. For that problem, you could use the conversions listed on the front of ...
by Rebecca Remple 1C
Sat Oct 12, 2019 2:55 pm
Forum: DeBroglie Equation
Topic: De Broglie equation
Replies: 5
Views: 29

Re: De Broglie equation

Hi Katherine,

I'm having trouble with the equation too, but I'm pretty sure mass is in kg because h is in J*s. 1 Joule is equivalent to 1kg⋅m2⋅s-2. Therefore, your mass being in kilograms will allow the units to cancel, so you can get wavelength in meters. I hope this helps!

-Rebecca
by Rebecca Remple 1C
Sat Oct 12, 2019 2:47 pm
Forum: Significant Figures
Topic: Significant Figures
Replies: 6
Views: 88

Re: Significant Figures

I agree with everything Rebekah said! To add onto it, sig figs are important when calculating your final answer. For example, if you were multiplying two numbers - 2.0 (2 sig figs) and 554.0 (4 sig figs) - your answer would have as many sig figs as the value with the lowest number of sig figs. The v...
by Rebecca Remple 1C
Sat Oct 12, 2019 2:41 pm
Forum: Significant Figures
Topic: Significant Figures and Molar Masses
Replies: 5
Views: 84

Re: Significant Figures and Molar Masses

I agree with the previous posters that constant values, like molar mass, should not count toward significant figures. Also, to add on to what Riya said, it's true that a whole number with zeroes like "300" only has one significant figure. However, if there is also a decimal point after thi...
by Rebecca Remple 1C
Sun Oct 06, 2019 5:52 pm
Forum: Einstein Equation
Topic: Energy Problem
Replies: 4
Views: 78

Re: Energy Problem

Hi there,

I solved the problem by plugging the minimum frequency into the equation E (energy) = h (Planck's constant, 6.626 * 10^-34) x v (wavelength). When I multiplied Planck's constant by the minimum frequency I got 7.22 x 10-19 J, which is the correct answer! I hope this helps :)

-Rebecca
by Rebecca Remple 1C
Sat Oct 05, 2019 4:40 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Wrong Textbook
Replies: 12
Views: 178

Re: Wrong Textbook

Hi McKenna, I had the 6th edition of the textbook and it is more or less the same as the 7th edition. I cross referenced the homework problems and they are exactly the same, although the page numbers can vary. However, if you have an older edition that does not align with the 7th edition, it can cau...
by Rebecca Remple 1C
Tue Oct 01, 2019 3:28 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Mole Units
Replies: 2
Views: 48

Re: Mole Units

Hi Rita, I think we're supposed to always abbreviate moles as "mol". For example, when reporting an answer in moles you should say "2 mol O2". Unfortunately, I don't think we could have moles of dogs, although that sounds adorable! A mole is defined as the quantity of anything th...
by Rebecca Remple 1C
Tue Oct 01, 2019 3:21 pm
Forum: Significant Figures
Topic: Sig Figs for Tests/Quizzes
Replies: 7
Views: 82

Re: Sig Figs for Tests/Quizzes

Hi Rita, I agree with Michael. In my past Chemistry experience, significant figures are taken pretty seriously. You should try to adhere to them, especially if the question specifically asks for them (e.g. if it says "round to 3 significant figures"). However, if the questions uses all who...

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