Search found 89 matches

by Audra Mcleod 3G
Wed Feb 24, 2021 11:07 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem 14BL Enrollment
Replies: 3
Views: 25

Re: Chem 14BL Enrollment

Hello!
Last quarter Dr. Casey let in everyone from the waitlist about two weeks before the quarter began!
by Audra Mcleod 3G
Wed Feb 24, 2021 11:00 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem community points
Replies: 12
Views: 47

Re: Chem community points

Hello! To my understanding you can only earn a maximum of 5 points per week. So if you don't make five posts one week but try to make it up with more posts another week, you'll still lose points. I would double check this with your TA, but until then I would complete the weekly five posts just to be...
by Audra Mcleod 3G
Fri Feb 19, 2021 11:45 pm
Forum: Student Social/Study Group
Topic: Post Midterm 2 De-stressing
Replies: 85
Views: 224

Re: Post Midterm 2 De-stressing

I unfortunately still have a fair amount of work to do over the weekend for Chem 14BL, but right after the midterm I went out to eat with my family which really helped unwind and forget about chemistry!
by Audra Mcleod 3G
Fri Feb 19, 2021 12:31 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Sapling #3 HELP (week 5 and 6)
Replies: 7
Views: 46

Re: Sapling #3 HELP (week 5 and 6)

Hello! So you know that the phase changes going from solid to liquid to gas are endothermic because they require breaking bonds, and thus the deltaH of the system is positive. On top of that, since the order of increasing entropy is solid < liquid < gas, you know that each of these phase changes inv...
by Audra Mcleod 3G
Thu Feb 18, 2021 1:54 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Textbook #4J13
Replies: 2
Views: 22

Textbook #4J13

Hello! I had a question on the following textbook question: Determine which of the following compounds are stable with respect to decomposition into their elements under standard conditions at 25 °C : (a) PCl5(g);(b) HCN(g); (c) NO(g); (d) SO2(g) The answer says that a and d are thermodynamically st...
by Audra Mcleod 3G
Tue Feb 16, 2021 11:15 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Units for Temperature
Replies: 5
Views: 17

Re: Units for Temperature

Hello!
Yes the units of temperature for this equation (and essentially all thermo equations) is Kelvin.
by Audra Mcleod 3G
Tue Feb 16, 2021 11:14 pm
Forum: Calculating Work of Expansion
Topic: When do I use w=-nRdeltaT
Replies: 1
Views: 17

Re: When do I use w=-nRdeltaT

Hello! I'm not exactly sure which equation you're referring to, as the closest one I can find is w = -nRTln(V2/V1). Also, since work is a measure of the energy expended moving an object against an opposing force, then that means when there is no change in volume then w = 0. In that sense, I believe ...
by Audra Mcleod 3G
Fri Feb 12, 2021 10:46 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: q equation
Replies: 21
Views: 52

Re: q equation

Hello! You would choose between these equations depending on whether you are given the specific heat capacity or the molar heat capacity. Since specific heat capacity is the amount of heat it takes to raise 1 gram of a substance by 1 degree celsius, then you would use the equation q = mCdeltaT since...
by Audra Mcleod 3G
Thu Feb 11, 2021 5:31 pm
Forum: Student Social/Study Group
Topic: Chem 14BL
Replies: 10
Views: 56

Re: Chem 14BL

Hello! I'm taking 14BL right now, and I can confirm it definitely would be a lot more work in person. Labs are a lot easier online since we no longer have to actually perform the experiment (don't have to master lab skills, don't have to worry about obtaining accurate data, etc. ), and often times m...
by Audra Mcleod 3G
Thu Feb 11, 2021 4:03 pm
Forum: Administrative Questions and Class Announcements
Topic: 14C First or Second Pass
Replies: 10
Views: 71

14C First or Second Pass

Hello! With first pass quickly approaching, I was wondering whether anybody had any knowledge about how difficult Chem 14C is to get into? Lavelle's chemistry classes have often had a lot of seats and have been lenient with the waitlist, but I don't know if 14C will be the same and whether I need to...
by Audra Mcleod 3G
Wed Feb 10, 2021 10:56 am
Forum: Student Social/Study Group
Topic: Midterm 2 study tips
Replies: 26
Views: 73

Re: Midterm 2 study tips

Personally, I like to review my notes, the textbook, and the practice problems, and then compile all the most important information on a google doc. I've found this to be very useful because it concentrates all the knowledge I need to know in one place, enabling me to more efficiently study. Again, ...
by Audra Mcleod 3G
Wed Feb 10, 2021 10:49 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 Content
Replies: 18
Views: 100

Re: Midterm 2 Content

Massimo_Capozza_1G wrote:What is the date and time of midterm 2?


Midterm 2 is on February 19th (next Friday) and can be at 11 am, 1 pm, or 3 pm depending on which lecture you're enrolled in!
by Audra Mcleod 3G
Fri Feb 05, 2021 11:19 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Weeks 3 and 4 Homework
Replies: 2
Views: 19

Re: Weeks 3 and 4 Homework

Hello! The equation you want to use here is: (# mol of ice)(enthalpy of fusion) + mass(cold)(specific heat of water)(Tfinal - temp of cold water) = - mass(hot)(specific heat of water)(Tf - temp of hot water) In the context of the equation, this will look like: (2.66 mol)(6.01x 10^3 J/mol) + (48 g)(4...
by Audra Mcleod 3G
Thu Feb 04, 2021 9:54 pm
Forum: Phase Changes & Related Calculations
Topic: Why does steam cause severe burns?
Replies: 22
Views: 55

Re: Why does steam cause severe burns?

Hello! When steam comes into contact with skin, the temperature difference between the two (with the skin being much lower in temperature) causes the steam to condense. In order to do so, the steam must release an amount of heat that corresponds to the enthalpy of vaporization, as this will enable i...
by Audra Mcleod 3G
Wed Feb 03, 2021 8:42 pm
Forum: Student Social/Study Group
Topic: Students Who Have a Job
Replies: 75
Views: 314

Re: Students Who Have a Job

Hello! I don't know if I belong on this post because I quit my job LOL, but I sympathize with everyone's comments. I worked about 15-20 hours per week last quarter, and while some weeks weren't that bad, it was overall a pretty stressful experience. It just felt like every time I had time to relax o...
by Audra Mcleod 3G
Wed Feb 03, 2021 7:34 pm
Forum: Administrative Questions and Class Announcements
Topic: Finishing outline 3
Replies: 3
Views: 43

Re: Finishing outline 3

Hello!
I believe today was the first lecture on the next section, so you'd be on the right track if you were to finish outline 3 problems before next week!
by Audra Mcleod 3G
Tue Feb 02, 2021 12:25 pm
Forum: Calculating Work of Expansion
Topic: different R constants
Replies: 7
Views: 23

Re: different R constants

Hello!
The equation sheet provided for this class has a list of all the gas constants and their corresponding units, so you can use this sheet as a reference for whenever you are doing problems that require using a gas constant!
by Audra Mcleod 3G
Sat Jan 30, 2021 9:48 pm
Forum: Administrative Questions and Class Announcements
Topic: Outlines and Lectures
Replies: 4
Views: 28

Re: Outlines and Lectures

Hello! As someone mentioned before, there's unfortunately no such resource available to us. The outline is intended to help you determine which particular topics you need to review some more, and you mainly have to find the related information on your own (through lectures, chem community, textbook,...
by Audra Mcleod 3G
Thu Jan 28, 2021 2:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook 6D3 (a)
Replies: 2
Views: 14

Re: Textbook 6D3 (a)

The .1 is the INITIAL concentration of the HClO2, not the equilibrium concentration. In the ICE table the equilibrium concentration would be .1-x, and we can calculate the value of x because we've been given the pH. By doing 10^-pH, we can determine the value of [H30+] to be .063, which would also b...
by Audra Mcleod 3G
Thu Jan 28, 2021 2:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Problem 6C.1
Replies: 2
Views: 30

Re: Textbook Problem 6C.1

These reactions involve the given compound reacting with water to form its conjugate acid/base and H30+/OH- ions. So for instance, the chemical equation for the proton transfer equilibrium in water of CN- would be: CN- + H20 --> HCN + OH-.
by Audra Mcleod 3G
Wed Jan 27, 2021 7:40 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Clarification about Solids & Liquids for Le Chateliers Principle
Replies: 7
Views: 61

Re: Clarification about Solids & Liquids for Le Chateliers Principle

Hello! I would agree that the concentrations of the products would not change here, since the shifting of a reaction as predicted by Le Chatelier's principle is a means for the reaction to reach equilibrium again. However, since pure solids and liquids are not included in the equilibrium constant eq...
by Audra Mcleod 3G
Wed Jan 27, 2021 7:29 pm
Forum: Student Social/Study Group
Topic: Spring 2021
Replies: 104
Views: 434

Re: Spring 2021

Hello! I'm currently taking Chem 14BL right now, and I just want to advise that this class, while not the most difficult material, is a lot of work. So if you think you are already going to have a busy schedule next quarter, you might want to consider whether you can handle this extra workload (week...
by Audra Mcleod 3G
Thu Jan 21, 2021 12:36 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Textbook 5.61
Replies: 3
Views: 19

Re: Textbook 5.61

Hello! According to Le Chatelier's principle, a reaction will adjust in order to minimize any changes that occurs. So in the instance that there is a change in the concentration of one chemical species, the reaction will shift in the direction that will alleviate the concentration imbalance between ...
by Audra Mcleod 3G
Wed Jan 20, 2021 8:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Where to find textbook answers
Replies: 4
Views: 28

Re: Where to find textbook answers

Hello!
In the table of contents for the online textbook, there should be a section called "Odd Numbered Exercises". This is where you'll find the answers to the assigned textbook questions.
by Audra Mcleod 3G
Wed Jan 20, 2021 8:48 pm
Forum: Phase Changes & Related Calculations
Topic: Steam vs. Water
Replies: 9
Views: 61

Re: Steam vs. Water

Hello! When steam comes into contact with skin, the temperature difference between the two (with the skin being much lower in temperature) causes the steam to condense. In order to do so, the steam must release an amount of heat that corresponds to the enthalpy of vaporization, as this will enable i...
by Audra Mcleod 3G
Wed Jan 20, 2021 7:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Simplifying K equations (book 5J.3)
Replies: 3
Views: 31

Re: Simplifying K equations (book 5J.3)

Hello! Do you perhaps have the wrong question number, because from what I see 5J.3 is asking about how changes in concentration affect the reaction / K value. Regardless, I doubt we'll ever be given an equation such as this when the K value is greater than 10^-4, as Lavelle has only ever assigned us...
by Audra Mcleod 3G
Tue Jan 19, 2021 12:10 pm
Forum: Ideal Gases
Topic: Gas Constant Value
Replies: 43
Views: 130

Gas Constant Value

Hello! I was wondering which gas constant we're supposed to use in this class when doing calculations with the ideal gas equation. I know there's multiple values for the gas constant, but the one I've seen most used in this class seems to be .08205. So is this gas constant the one we'll predominatel...
by Audra Mcleod 3G
Fri Jan 15, 2021 3:16 pm
Forum: General Science Questions
Topic: Significant Figures and Rounding
Replies: 9
Views: 41

Re: Significant Figures and Rounding

Hello! Significant figures/ Rounding are not of the utmost importance in this quarter, since the online format of this class means that our exams will be multiple choice, and therefore the rounded answers will be given to us with the appropriate sig figs. Also on the Sapling homework, it appears tha...
by Audra Mcleod 3G
Thu Jan 14, 2021 4:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solids and liquids in K expression
Replies: 7
Views: 35

Re: solids and liquids in K expression

Kaylee Nezwek_2G wrote:Ah, thank you! So just to clarify, if a substance is purely a solid/liquid then we would not include it in the K expression, but aqueous solutions are okay to include?


Yes! We definitely use aqueous solutions in the equilibrium constant equation.
by Audra Mcleod 3G
Thu Jan 14, 2021 4:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solids and liquids in K expression
Replies: 7
Views: 35

Re: solids and liquids in K expression

Hello! We never include liquids and solids in the equilibrium equations. In the chemical reaction you mentioned, the equilibrium constant equation was [H30+][OH-] not [H30+][OH-] / [H20]. This is mainly because: 1. solids do not have concentrations 2. Liquids/solvents are often present in such large...
by Audra Mcleod 3G
Thu Jan 14, 2021 12:37 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Sapling week 1 #5 [ENDORSED]
Replies: 3
Views: 68

Re: Sapling week 1 #10 [ENDORSED]

Hello! To solve this you must multiply the equilibrium constants of the two constituent equations, which would be the equations in which HI and NH3 are the products. You'll have to make some conversions though, because you'll notice that the primary equation is not identical to the given equations.F...
by Audra Mcleod 3G
Wed Jan 13, 2021 7:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Distinguishing weak acids and weak bases
Replies: 3
Views: 38

Re: Distinguishing weak acids and weak bases

There are 3 main ways to distinguish an acid from a base: 1. An acid increases hydronium ion concentration (H3O+) in water, while a base increases hydroxide ion concentration (OH-) in water 2. An acid is a proton donor, while a base is a proton acceptor 3. An acid is an electron pair acceptor, while...
by Audra Mcleod 3G
Wed Jan 13, 2021 7:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH and pOH conceptually
Replies: 3
Views: 23

Re: pH and pOH conceptually

Hello!
I also believe, unless Lavelle tells/shows us any differently, pH and pOH are measured from reactions with water, given that this is one of the foremost ways in which we've seen H30+ and OH- ions produced.
by Audra Mcleod 3G
Fri Jan 08, 2021 12:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Picking answer from quadratic solutions
Replies: 12
Views: 57

Re: Picking answer from quadratic solutions

Hello!
When both answers for your quadratic equation are positive, you pick the number that is less than the initial concentrations you are given.
by Audra Mcleod 3G
Fri Jan 08, 2021 12:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE tables
Replies: 8
Views: 67

Re: ICE tables

Hello! Given that Lavelle has used molarity in his examples fo ICE tables, I believe this indicates that this is an appropriate unit to use. Also, considering you often are required to give your final answer as concentration in these questions, I think it would make sense to immediately make the con...
by Audra Mcleod 3G
Thu Jan 07, 2021 3:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Homework Week Q3
Replies: 3
Views: 53

Re: Sapling Homework Week Q3

Hello! You would multiply the two concentrations of the reactants (.7-X) to receive a quadratic equation, and then multiply this equation by the value of Kc. Finally subtract the value of [HI]^2 (which should be 4x^2) from the left so you would have your final quadratic equation equal to 0. You can ...
by Audra Mcleod 3G
Thu Jan 07, 2021 3:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Preset values of K
Replies: 5
Views: 38

Re: Preset values of K

Hello! The value of K for a reaction does in fact correlate to certain conditions, and will be a different number when the reaction takes place under new parameters. For instance, the value of K is always temperature dependent, so anytime the temperature is altered there will be a corresponding chan...
by Audra Mcleod 3G
Thu Jan 07, 2021 2:59 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Positive and negative delta H
Replies: 5
Views: 28

Re: Positive and negative delta H

Hello! I think you've confused what is the system in this scenario. The system is the chemical reaction, not the environment in which the reaction is taking place. Given this perspective, when deltaH is positive, that means that the reaction has absorbed heat, and thus the reaction is endothermic ( ...
by Audra Mcleod 3G
Thu Jan 07, 2021 2:45 pm
Forum: Ideal Gases
Topic: Kc for Gases
Replies: 11
Views: 81

Kc for Gases

Hello! I was under the impression that when incorporating gases into an equilibrium constant equation, you always use their partial pressures. However, I've seen examples where you were asked to find the Kc value, and instead the molar concentrations of the gases were used. So I was wondering whethe...
by Audra Mcleod 3G
Thu Dec 10, 2020 11:10 am
Forum: Conjugate Acids & Bases
Topic: Deriving from Strong Base/Acid?
Replies: 2
Views: 26

Re: Deriving from Strong Base/Acid?

Hello! As said in the previous reply, you have to determine whether the anion and cation came from a strong or weak base/acid in order to determine whether they will affect the pH of a solution. To elaborate on that: 1. The cation will likely come from a strong/weak base, and if you determine the ca...
by Audra Mcleod 3G
Wed Dec 09, 2020 1:05 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Strong Bases
Replies: 2
Views: 37

Strong Bases

Hello! I was kind of confused as to whether metal oxides were considered strong bases. I know that in lecture Lavelle said groups 1 and 2 hydroxides and oxides were strong, but the list of strong bases that Sapling provided only included groups 1 and 2 hydroxides (and said that any bases not in that...
by Audra Mcleod 3G
Tue Dec 08, 2020 10:22 am
Forum: Significant Figures
Topic: Things to remember for final?
Replies: 20
Views: 159

Re: Things to remember for final?

Hello! I would say have the strong acids memorized, because while there are some key characteristics of strong bases you can know (group 1 and 2 oxides/hydroxides) that will make memorizing all of their names unnecessary, there are no such common trends amongst the strong acids. Also, there are only...
by Audra Mcleod 3G
Tue Dec 08, 2020 10:17 am
Forum: Determining Molecular Shape (VSEPR)
Topic: textbook #2E13
Replies: 4
Views: 47

Re: textbook #2E13

Hello! So we know the central I has 5 regions of electron density (3 lone pairs and 2 bound atoms), meaning its electron arrangement is trigonal bipyramidal. In order to determine the shape from this, we need to place the lone pairs in positions where their repulsion will be minimized. This ideally ...
by Audra Mcleod 3G
Tue Dec 08, 2020 10:10 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Geometry & Electron Density
Replies: 5
Views: 32

Re: Molecular Geometry & Electron Density

Hello! Whenever you are told to find the shape, it is referring to the the molecular geometry, whose name only depends on the arrangement of the atoms around the central atom. Electron arrangement, on the other hand, involves all regions of electron densities surrounding the central atom, including ...
by Audra Mcleod 3G
Thu Dec 03, 2020 11:55 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Determining Monodentate, Bidentate, etc.
Replies: 2
Views: 24

Determining Monodentate, Bidentate, etc.

Hello! I'm really confused as to how you determine whether a ligand is monodentate, bidentate, polydentate, etc. . I understand what these terms mean, I just don't know how I can determine the number of donor atoms a ligand possesses from the coordination compound formula. I assume it's related to d...
by Audra Mcleod 3G
Thu Dec 03, 2020 11:33 am
Forum: Bronsted Acids & Bases
Topic: Bronsted Acids Strength
Replies: 3
Views: 28

Re: Bronsted Acids Strength

Hello! An acid's strength is determined by the extent to which it ionizes in a solution, and in order to ionize the acid must dissociate into ions. Since this would require the bonds between the atoms in the acid to break, then acids consisting of weaker bonds will be considered stronger as they wil...
by Audra Mcleod 3G
Thu Dec 03, 2020 11:19 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: pH Chart
Replies: 16
Views: 125

Re: pH Chart

Hello!
I don't think you need to memorize the entire chart, but I think remembering significant pH levels would be beneficial. For instance, that pH levels range from 0-14, with 7 being neutral, <7 being acidic, and >7 being basic.
by Audra Mcleod 3G
Thu Dec 03, 2020 11:11 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ammonia vs Ammine
Replies: 3
Views: 14

Re: Ammonia vs Ammine

Hello!
Yes, ammine refers to an ammonia molecule that has attached to a transition metal as a ligand, and is now apart of a coordination compound.
by Audra Mcleod 3G
Wed Dec 02, 2020 10:14 am
Forum: Student Social/Study Group
Topic: Final Exam Study Tips
Replies: 48
Views: 283

Re: Final Exam Study Tips

Personally, I like to review my notes, the textbook, and the practice problems, and then compile all the most important information on a google doc. I've found this to be very useful because it concentrates all the knowledge I need to know in one place, enabling me to more efficiently study. Again, ...
by Audra Mcleod 3G
Thu Nov 26, 2020 12:40 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem 14B
Replies: 5
Views: 67

Re: Chem 14B

Hello!
Your situation may be problematic in the future, and not because of lecture recordings. Lavelle said in his most recent email that tests for Chem 14B will be held during lecture sessions instead of TA sessions, so you may have to miss your other class in order to complete Chem 14B exams.
by Audra Mcleod 3G
Wed Nov 25, 2020 9:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Weeks 7&8 Question 17
Replies: 1
Views: 14

Re: Sapling Weeks 7&8 Question 17

Hello! I was also stuck on this problem for a while, mainly because the three desired structures were all very different from one another. These structures would be: 1. The three Cs are in a line, with two hydrogens attached to each outer C. The C in the middle is double bonded to both Cs next to it...
by Audra Mcleod 3G
Wed Nov 25, 2020 9:13 pm
Forum: Biological Examples
Topic: Cisplatin Cell Division Question
Replies: 2
Views: 35

Re: Cisplatin Cell Division Question

Hello! From what I gathered from Lavelle's explanation, the reason cisplatin wouldn't cause additional errors and mutations in the cell's DNA is because it stops the replication process entirely, before any such mistakes can be made. Moreover, its effect on the cell's DNA would induce apoptosis, and...
by Audra Mcleod 3G
Tue Nov 24, 2020 2:09 pm
Forum: General Science Questions
Topic: Sapling #8
Replies: 4
Views: 42

Re: Sapling #8

Hello!
The bonds between Be and Cl would be polar due to the large electronegativity difference between these two atoms, but the molecule would be non polar as a whole because the pull of the two Cls would cancel out.
by Audra Mcleod 3G
Tue Nov 24, 2020 1:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape vs. Electron Arrangement
Replies: 4
Views: 46

Re: Shape vs. Electron Arrangement

Hello! The electron arrangement of a molecule takes into account all regions of electron density around the central atom, and thus includes both lone pairs and bonding atoms. Shape, on the other hand, will only take into account bonding atoms. For instance, NH3 has a tetrahedral electron arrangement...
by Audra Mcleod 3G
Thu Nov 19, 2020 10:32 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook 2A.9
Replies: 2
Views: 16

Re: Textbook 2A.9

Just to add on to the above answer, remember when you are determining the electron configuration of ions, you must remove/add electrons from the highest energy level. So while the cations in question are in the 3d block, you would first remove the electrons from the 4s orbital, as this is higher in ...
by Audra Mcleod 3G
Wed Nov 18, 2020 1:44 pm
Forum: Administrative Questions and Class Announcements
Topic: MT2 Electronegativity Values
Replies: 1
Views: 39

Re: MT2 Electronegativity Values

I highly doubt you'll be given any electronegativity values on the midterm, so I'd recommend memorizing the general trend. Electronegativity generally increases left to right across a period and decreases as you go down a group (high ionization energy/electron affinity = high electronegativity), wit...
by Audra Mcleod 3G
Wed Nov 18, 2020 1:35 pm
Forum: Lewis Structures
Topic: Lewis Structure Covalent Bonds
Replies: 2
Views: 24

Re: Lewis Structure Covalent Bonds

Hello! As someone mentioned above, there are some lewis structures that represent ionic structures, but they will involve an entirely different format than the ones we have been primarily focusing on in class. The lewis structures we've mainly seen, in which atoms are connected by lines/dots, all de...
by Audra Mcleod 3G
Wed Nov 18, 2020 1:16 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 Scores
Replies: 2
Views: 92

Midterm 2 Scores

Hello!
Will the scores for Midterm 2 be released earlier than those for Midterm 1 considering there will be no partial credit to calculate?
by Audra Mcleod 3G
Wed Nov 18, 2020 1:09 pm
Forum: Lewis Structures
Topic: Sapling #4
Replies: 3
Views: 39

Re: Sapling #4

Hello!
While all resonance structure contribute to the overall structure, some will contribute more than others due to their favorable formal charges and increased stability. So in this particular question, it's asking you to produce the lewis structure that minimizes its formal charges.
by Audra Mcleod 3G
Wed Nov 11, 2020 12:56 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook problem 1.D.13
Replies: 3
Views: 31

Re: Textbook problem 1.D.13

Hello! Ml can be determined from the value of l, in which the ml values will range from: -l... 0...+l. Since the problem gives the 6d orbital, we know that the l value is 2 since a d orbital correspond to l=2. With this information, we now know that there will be 5 values of ml, which will include -...
by Audra Mcleod 3G
Wed Nov 11, 2020 12:49 pm
Forum: Electronegativity
Topic: Determining Permanent Dipole
Replies: 3
Views: 48

Determining Permanent Dipole

Hello! I've had difficulty with determining whether a molecule will exhibit dipole-dipole interactions, and I've realized it's largely because I don't know how you can tell whether a molecule has a permanent dipole. I understand that a dipole will be present when there is a high electronegativity di...
by Audra Mcleod 3G
Wed Nov 11, 2020 12:36 pm
Forum: Bond Lengths & Energies
Topic: Bond Strength Clarification
Replies: 5
Views: 76

Re: Bond Strength Clarification

Hello! Yes, bonds between larger atoms are longer and weaker as compared to bonds between smaller atoms, due to the fact that the increased atomic radii of these large atoms prevents them from coming into close contact with one another. In regards to molecules, I'd also assume that larger molecules ...
by Audra Mcleod 3G
Wed Nov 11, 2020 12:14 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework Problem #3
Replies: 2
Views: 35

Re: Homework Problem #3

Hello! In this problem, you have to draw the lewis structures of nitrite (NO2-), nitrate (NO3-), phosphite (PO3 -3), and phosphate (PO4 -3), but the main focus is to draw the structure that minimizes the formal charge. This would involve using double bonds between the central atoms and oxygen atoms ...
by Audra Mcleod 3G
Wed Nov 11, 2020 11:56 am
Forum: Bond Lengths & Energies
Topic: Van der Waals
Replies: 7
Views: 95

Re: Van der Waals

The strength of Van der Waals forces also depends on the polarizability of the molecule (and therefore will be stronger within larger, heavier molecules) as well as the distance between molecules (stronger when distance is small).
by Audra Mcleod 3G
Fri Nov 06, 2020 3:27 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing Power
Replies: 5
Views: 40

Re: Polarizing Power

Hello! To elaborate on why an increase in atomic size corresponds to increased polarizability, when an atom has a larger atomic radius, this results in the pull of the nucleus on the electrons being weakened (from increased distance and electron shielding). Consequently, these electrons are more eas...
by Audra Mcleod 3G
Fri Nov 06, 2020 3:17 pm
Forum: Resonance Structures
Topic: resonance structures
Replies: 8
Views: 69

Re: resonance structures

Hello! Resonance structures are a group of Lewis structures that all describe the electron bonding of the same molecule, but depict the same bond in different locations. For instance, the lewis structure for NO3- involves N having a single bond with two O atoms and a double bond with one O atom, but...
by Audra Mcleod 3G
Fri Nov 06, 2020 2:59 pm
Forum: Ionic & Covalent Bonds
Topic: Electronegativity Difference Between 1.5 and 2
Replies: 4
Views: 60

Re: Electronegativity Difference Between 1.5 and 2

Hello! Based on what Lavelle stated in lecture, when determining the type of bond of a compound with an electronegativity between 1.5 and 2, you have to study its unique properties in depth in order to see whether it behaves more as a salt or molecule. This would involve, for instance, observing its...
by Audra Mcleod 3G
Thu Nov 05, 2020 11:20 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration States
Replies: 2
Views: 47

Electron Configuration States

Hello!
So I'm aware that initially the 4s state is lower in energy than the 3d state, and therefore would go before it in an electron configuration until after calcium. However, I was wondering whether this phenomenon applied to any other states, such as 5s and 4d?
by Audra Mcleod 3G
Thu Nov 05, 2020 11:03 am
Forum: Formal Charge and Oxidation Numbers
Topic: most stable lewis structure/formal charge
Replies: 6
Views: 84

Re: most stable lewis structure/formal charge

Hello! In regards to the possibility of a sulfur atom having four double bonds, I'm almost certain it's impossible. Even though Lavelle has mentioned that S can have an expanded octet, four double bonds would correspond to 16 electrons, and the maximum amount of valence electrons S can accommodate i...
by Audra Mcleod 3G
Fri Oct 30, 2020 1:31 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Shorthand Electron Configurations
Replies: 6
Views: 48

Shorthand Electron Configurations

Hello! I had a question on how to write electron configurations using the shorthand method, specifically how you know which orbitals you start with after you write the noble gas symbol. For instance, the electron configuration for iodine is [Kr] 3d^10 5s^2 5p^5, how would you know to start at 3d? I ...
by Audra Mcleod 3G
Thu Oct 29, 2020 2:39 pm
Forum: Student Social/Study Group
Topic: Midterm Grades
Replies: 5
Views: 84

Re: Midterm Grades

Hello!
To my knowledge, we will not receive our midterm grades until the last chemistry discussion section has completed the test. So the end of this week should be a realistic time to expect our scores to be returned.
by Audra Mcleod 3G
Thu Oct 29, 2020 2:37 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: En and E
Replies: 3
Views: 43

Re: En and E

Hello! Just as you assumed, E and En are not the same. The symbol En represents the energy of an energy level within an atom, as shown by the equation En = -hR/n^2. E, on the other hand, I think is a little more complicated as I've seen it used in a variety of contexts. Overall, it can be used as th...
by Audra Mcleod 3G
Thu Oct 29, 2020 2:26 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration
Replies: 5
Views: 34

Re: Electron Configuration

Hello!
Based on how the electron configuration questions were formatted on the Sapling homework, I assume the default is the full electron configuration, and that we would only use noble gas symbols in the configuration when explicitly asked to do so.
by Audra Mcleod 3G
Mon Oct 26, 2020 9:05 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Inconsistencies in Delta Values
Replies: 4
Views: 53

Re: Inconsistencies in Delta Values

Hello!
The answer to this problem is most definitely an error, as the uncertainty in velocity would be 10 m/s not 5. Mr. Lavelle corrected this in his "Solution Manuel Errors 7th Edition" on his website, and included the correct answer.
by Audra Mcleod 3G
Thu Oct 22, 2020 3:29 pm
Forum: Photoelectric Effect
Topic: Textbook Problem 1A. 9
Replies: 4
Views: 46

Re: Textbook Problem 1A. 9

Hello! The problem involves four empty rows, in which each one only provides you one of the following: wavelength, frequency, and energy of photon. You would use the equations E = hv and c=(frequency)(wavelength) to determine the missing characteristics of each form of radiation, and then use the fr...
by Audra Mcleod 3G
Thu Oct 22, 2020 2:56 pm
Forum: Einstein Equation
Topic: Textbook problem B.7
Replies: 2
Views: 62

Re: Textbook problem B.7

Hello! a) So to determine the energy of an excited sodium atom, you would first use the wavelength to determine the frequency of the light emitted through the equation speed of light =(wavelength)(frequency). This would give you 5.093 x 10^14 (3.0x10^8/589x10^-9). You would then use this frequency i...
by Audra Mcleod 3G
Wed Oct 21, 2020 8:23 pm
Forum: Properties of Electrons
Topic: Electrons Having Wavelike Properties
Replies: 2
Views: 40

Re: Electrons Having Wavelike Properties

Hello! So in the general diffraction experiment involving an electron beam being shot through two slits, there is a screen behind the slits that will record where the electrons hit. If electrons were behaving as particles in this experiment, they would simply continue along their path and create two...
by Audra Mcleod 3G
Wed Oct 21, 2020 6:02 pm
Forum: Administrative Questions and Class Announcements
Topic: Periodic Table for Midterm 1
Replies: 1
Views: 43

Periodic Table for Midterm 1

Hello! I had a quick question regrading the appropriate atomic masses to use for Midterm 1. On the periodic table Lavelle provides for us, the atomic masses can have as many as 5 decimal places, whereas on one of my personal periodic tables the masses only go to the hundredth place. I was wondering ...
by Audra Mcleod 3G
Wed Oct 21, 2020 5:00 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: S Orbitals and nodal planes
Replies: 5
Views: 61

Re: S Orbitals and nodal planes

Hello! I'm not too sure myself about the second part of your question, but I am almost certain that your first question regarding the fact that s orbitals do not have a point where the electron density is zero is true. In his lecture, Lavelle did not indicate that there were any other areas in an or...
by Audra Mcleod 3G
Thu Oct 15, 2020 12:31 pm
Forum: Properties of Light
Topic: Electron diffraction
Replies: 5
Views: 48

Re: Electron diffraction

Hello! To further elaborate, diffraction patterns are interference patterns that emerge from constructive and destructive interference. Constructive interference results from in-phase waves interacting (the peaks of each wave overlap and the troughs of each wave overlap), and destructive interferenc...
by Audra Mcleod 3G
Wed Oct 14, 2020 8:11 pm
Forum: Properties of Light
Topic: Exercise 1A.15
Replies: 2
Views: 58

Re: Exercise 1A.15

Hello! So the first thing you need to know about this problem is that since the line is within the UV spectrum of atomic hydrogen, then it is apart of the Lyman series, and therefore its lowest energy level will be n=1 (this is stated in the reading of the textbook). So you now know that the electro...
by Audra Mcleod 3G
Wed Oct 14, 2020 6:03 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Module #39
Replies: 1
Views: 38

Re: Module #39

Hello! To solve this problem, you would first have to determine the change in energy. You will have to determine the energy of each energy level through the equation En = -hR/n^2, and since you were given each energy level (2 and 4), you would simply plug these values in. Then you would use the equa...
by Audra Mcleod 3G
Tue Oct 13, 2020 1:24 pm
Forum: Einstein Equation
Topic: Textbook problem 1B 7?
Replies: 3
Views: 40

Re: Textbook problem 1B 7?

Hello! a) So to determine the energy of an excited sodium atom, you would first use the wavelength to determine the frequency of the light emitted through the equation speed of light =(wavelength)(frequency). This would give you 5.093 x 10^14 (3.0x10^8/589x10^-9). You would then use this frequency i...
by Audra Mcleod 3G
Tue Oct 13, 2020 12:30 pm
Forum: Photoelectric Effect
Topic: Textbook Question 1B15
Replies: 4
Views: 46

Textbook Question 1B15

Hello! I was stuck on question A of the textbook question 1B15, which was the following: The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x 10^3 km/sec a)What is the wavelength of the ejected electron? I'm just confused as to how to go from velocity to wavelengt...
by Audra Mcleod 3G
Fri Oct 09, 2020 5:05 pm
Forum: Molarity, Solutions, Dilutions
Topic: sapling hw #7
Replies: 17
Views: 165

Re: sapling hw #7

Hello! For this problem the solution is easier than you would think. To find the mass of calcium chloride you multiply .325 with 590.1 g (giving you about 191.78 g), as you know that calcium chloride would constitute 32.5% of the total mass of this mixture. Then to find the mass of the water, you wo...
by Audra Mcleod 3G
Thu Oct 08, 2020 2:39 pm
Forum: Significant Figures
Topic: Significant Figures about Logarithms
Replies: 4
Views: 46

Re: Significant Figures about Logarithms

I'm not entirely sure about logarithms, but I know that for scientific notation the number of sig figs is determined by the number to the left of the multiplication sign. For instance, 8.32 x 10^3 has 3 sig figs and 1.00026 x 10^-4 has 6 sig figs.
by Audra Mcleod 3G
Thu Oct 08, 2020 2:26 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Confidence Interval and Accuracy & Precision
Replies: 5
Views: 62

Re: Confidence Interval and Accuracy & Precision

This was a very intriguing observation for me considering I've always loved statistics! It also makes a lot of sense since wider confidence intervals have always been associated with a higher degree of accuracy (hence the higher confidence level), due to the fact that since they encompass a wider ra...
by Audra Mcleod 3G
Thu Oct 08, 2020 2:17 pm
Forum: General Science Questions
Topic: Credit for community forum [ENDORSED]
Replies: 7
Views: 92

Re: Credit for community forum [ENDORSED]

Everything in the above comments is accurate, and just remember to be committed to fulfilling your Chemistry Community points as they'll account for a total of 50 points by the end of the quarter!
by Audra Mcleod 3G
Thu Oct 08, 2020 2:08 pm
Forum: Student Social/Study Group
Topic: Textbook Readings on Fundamental Topics
Replies: 5
Views: 58

Re: Textbook Readings on Fundamental Topics

To my understanding, a concept/problem that wasn't even mentioned at any point during the course seems like unrealistic material to expect on any exams. Instead, one of my UAs said that it is not uncommon for Lavelle to use homework questions verbatim on tests, and therefore the questions listed on ...

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