## Search found 61 matches

Sat Jan 16, 2021 10:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw constant
Replies: 25
Views: 50

### Re: Kw constant

If you don't want to understand why: just remember we always leave out solids and liquids, molecules with the (s) and (l) subscript. If you want to know why, its because the reaction is happening in a solution of water, that means there are TREMENDOUS amounts of water compared to the other molecules...
Sat Jan 16, 2021 10:38 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ka vs kb
Replies: 20
Views: 55

### Re: ka vs kb

Yes you are correct, don't forget the relationship between the two: Ka x Kb = Kw = 10-14
Sat Jan 16, 2021 10:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #1 (Week 2)
Replies: 4
Views: 28

### Re: Sapling #1 (Week 2)

Think of this question like it came from last week (the Ka is your K value... which you will use in your k expression. Set up your ice table by using the concentration given to you for the initial acid concentration. And calculate from there!
Sat Jan 16, 2021 10:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Week 2 Problem 10
Replies: 1
Views: 41

### Sapling Week 2 Problem 10

Can someone explain the reasoning behind why comparing the Pka and pH values will determine whether the solution is charged or neutral such as that in the last two questions of our sapling hw?
Sat Jan 16, 2021 10:30 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 1
Replies: 20
Views: 98

### Re: Midterm 1

Taylor Newville 1C wrote:Can someone who had Lavelle last quarter for 14A explain what his midterms are like?

A lot of the questions are quite similar to the tougher textbook problems so definitely brush up on those!
Fri Jan 08, 2021 12:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE tables
Replies: 8
Views: 40

### Re: ICE tables

Hi, I have followed the textbook and I believe it has been using molarity. I find just staying in molarity easier because most answers want molarity anyways, so just convert from the very beginning and you should be good!
Fri Jan 08, 2021 12:19 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic and Endothermic
Replies: 4
Views: 23

### Exothermic and Endothermic

I've always struggled to picture the relation between what an exothermic/endothermic reaction means with relation to a system and to whether the DeltaH is positive or negative, does anyone have mnemonic strategies or ways of thinking to clear that up?
Fri Jan 08, 2021 12:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Shortcuts in EQ Calcs
Replies: 5
Views: 35

### Shortcuts in EQ Calcs

Im confused on when you can neglect the x component in the denominator sometimes. In example 5I.3, the textbook says approximate x<3.21 & 6.21 So in the solving for x in the equation equal to K, the x's in the denominator are just crossed out? When can we do this/when can we not? Because I'm sur...
Fri Jan 08, 2021 12:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Problem 5.39
Replies: 6
Views: 61

### Textbook Problem 5.39

In an experiment, 0.020 mol NO2 was introduced into a flask of volume 1.00 L and the reaction 2NO2(g)⇌N2O4(g) was allowed to come to equilibrium at 298 K. (a) Using information in Table 5G.2, calculate the equilibrium concentrations of the two gases. (b) The volume of the flask is reduced to half it...
Fri Jan 08, 2021 12:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Replies: 12
Views: 46

So in a lot of the equilibrium calculations we end up using the quadratic formula/or polysmlt on the calculator to find the two roots.
My question is how do we know which one to pick when they are both positive? Is it always the one closer to 0? (when both are positive?)
Thu Dec 10, 2020 3:01 pm
Forum: General Science Questions
Topic: Textbook Questions on the Final
Replies: 11
Views: 93

### Re: Textbook Questions on the Final

I doubt every single question will be from the textbook but I would assume a decent chunk of them will be.
Thu Dec 10, 2020 2:31 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Textbook Problem 6C.21
Replies: 1
Views: 33

### Textbook Problem 6C.21

Can someone explain part B... why formic acid is actually stronger than acetic acid.

Suggest an explanation for the different strengths of (a) acetic acid and trichloroacetic acid; (b) acetic acid and formic acid.
Thu Dec 10, 2020 2:24 pm
Forum: Polyprotic Acids & Bases
Topic: Textbook Problem 6C.17
Replies: 3
Views: 41

### Textbook Problem 6C.17

Can someone explain the reasoning behind why the answer is hypobromite?

Which is the stronger base, the hypobromite ion, BrO−, or morphine, C17H19O3NC17H19O3N? Justify your answer.
Thu Dec 10, 2020 1:55 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Textbook Problem 6B.3
Replies: 1
Views: 19

### Textbook Problem 6B.3

Can anyone explain the steps to solve this problem? 6B.3 A careless laboratory technician wants to prepare 200.0 mL of a 0.025 M HCl(aq) solution but uses a volumetric flask of volume 250.0 mL by mistake. (a) What would the pH of the desired solution have been? (b) What will be the actual pH of the ...
Thu Dec 10, 2020 1:45 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Textbook Question 6B.1
Replies: 4
Views: 52

### Textbook Question 6B.1

Im a little confused on where to start for this question

The molar concentration of HCl in hydrochloric acid is reduced to 12% of its initial value by dilution. What is the difference in the pH values of the two solutions?
Fri Dec 04, 2020 10:37 am
Forum: General Science Questions
Topic: curve
Replies: 16
Views: 152

### Re: curve

I heard that there is really no chance of a curve in this class. I really hope he doesn't consider a downcurve.
Fri Dec 04, 2020 10:36 am
Forum: Lewis Acids & Bases
Topic: lewis vs bronsted
Replies: 8
Views: 87

### Re: lewis vs bronsted

So Bronsted acids and bases are taking with respect to proton donating/accepting. Lewis acids and bases are with respect to donating/accepting electrons.
Fri Dec 04, 2020 10:35 am
Forum: Student Social/Study Group
Topic: Thoughts on Switching Majors?
Replies: 29
Views: 230

### Re: Thoughts on Switching Majors?

I actually have decided I will be switching majors after knowing a bit more about my major this quarter. Currently I am a biology major however, I was looking at the upper division classes that I would need to take and I do not think I would be particularly interested in those so I'm thinking of swi...
Wed Dec 02, 2020 2:25 pm
Forum: Naming
Topic: C03 2- mono/bi
Replies: 1
Views: 25

### C03 2- mono/bi

In textbook problem 9C.5b it asks whether CO32- is polydentate or not. The answer keys states that it can be mono dentate or bidentate, how can this molecule have two options... I especially do not see how bidentate is possible.
Wed Dec 02, 2020 2:23 pm
Forum: Naming
Topic: Iron naming
Replies: 1
Views: 21

### Iron naming

I was wondering what you would use for Fe when the complex does not have a negative charge. All the textbook problems end up having that complex with a negative charge for iron so it becomes ferrate, but if the complex was positive it wouldn't be ferr would it?
Fri Nov 27, 2020 5:54 pm
Forum: SI Units, Unit Conversions
Topic: How to memorize prefixes
Replies: 22
Views: 195

### Re: How to memorize prefixes

I just use flashcards or just memorize them straight up because many of them are used so often in all STEM based classes.
Fri Nov 27, 2020 5:49 pm
Forum: Naming
Topic: Naming Complexes
Replies: 7
Views: 64

### Naming Complexes

Im confused because I've started the textbook problems for this section but many of them require us to come up with the names for the compounds. Are we required to learn the nomenclature rules for this section, I simply assumed we didn't because Lavelle didn't cover it in his lectures (at least for ...
Fri Nov 27, 2020 5:46 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordination number
Replies: 13
Views: 83

### Re: coordination number

I reflect everything everyone has said above, but also be wary the coordination number is for every bond that attaches to the central atom (make sure you don't ever count the bonds between say the C and N.
Fri Nov 27, 2020 5:45 pm
Forum: Resonance Structures
Topic: Sapling Week 7/8 Question 17
Replies: 3
Views: 45

### Re: Sapling Week 7/8 Question 17

I struggled with this one so I ended up just submitting the answer and looking for the hints. Im sure you found the first one, the second one has a triple bond and is still linear, the last one is super tricky because is forms a triangular ring. Hope that guides you in the right direction!
Fri Nov 27, 2020 5:43 pm
Forum: Properties of Electrons
Topic: degenerate orbital
Replies: 6
Views: 67

### Re: degenerate orbital

Degenerate orbitals are defined as orbitals that have the same energy.
Fri Nov 20, 2020 12:57 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angles
Replies: 16
Views: 248

### Re: bond angles

Professor Lavelle referenced in his lecture that repulsion strength goes in this order (LP-LP, LP-atom, atom-atom) thus the lone pairs will exert a bigger repulsive force on the other atoms making the other atoms get closer together (becomes less than 120 degrees or 109.5 what have you) so the LP ca...
Fri Nov 20, 2020 12:55 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: LDF forces
Replies: 9
Views: 74

### Re: LDF forces

All molecules exhibit LDF forces, many molecules have other forces as well such as ion-ion!
Fri Nov 20, 2020 12:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework
Replies: 2
Views: 37

### Re: Homework

Axial is referring the axis position (the vertical axis), and equatorial are the ones surrounding the middle (think the equator of a globe) and the north and South Pole are the axes.
Fri Nov 20, 2020 12:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear VSEPR issues
Replies: 3
Views: 38

### Linear VSEPR issues

Linear arrangements seem pretty easy but there are some specifics where I get confused. In I 3 - , the molecule is linear however the central atom has 3 lone pairs, is the reason why it is still linear because they are all I atoms and have the same electronegativity and thus any L.P's will arrange s...
Thu Nov 19, 2020 7:32 pm
Forum: Ionic & Covalent Bonds
Topic: Polar Covalent Bond
Replies: 8
Views: 62

### Re: Polar Covalent Bond

Regarding your first question, yes you can tell if bonds will be polar covalent bonds if you determine there is a difference in the electronegativities of the two atoms involved. However, the MOLECULE may be non-polar even if all the BONDS-WITHIN are polar because sometimes the shape can be symmetri...
Thu Nov 19, 2020 7:26 pm
Forum: Resonance Structures
Topic: Lowest Energy Lewis Structure
Replies: 8
Views: 83

### Re: Lowest Energy Lewis Structure

Yes, if you are unable to attain a structure with 0 formal charge on all the atoms you generally should draw the lewis structure in a formation that puts negative formal charges on the more electronegative atoms (typically the non-central atoms).
Fri Nov 13, 2020 10:24 pm
Forum: Student Social/Study Group
Replies: 110
Views: 1161

### Re: grade worries

I relate to a lot of you on this. I will calculate how many more points I can miss altogether or even on my next midterm before I lose my chances of getting an A. Its especially worrying when the midterms have such few questions that one question can make you lose a lot of points. I think the best t...
Fri Nov 13, 2020 10:21 pm
Forum: Administrative Questions and Class Announcements
Topic: Subtitles
Replies: 4
Views: 49

### Re: Subtitles

I do not believe that there is a subtitle feature for these bruin casts. However, like many people have pointed out you can speed or slow down Professor Lavelle's lectures which can be really helpful.
Fri Nov 13, 2020 10:20 pm
Forum: Administrative Questions and Class Announcements
Topic: How to Treat Anions and Cations
Replies: 4
Views: 47

### Re: How to Treat Anions and Cations

Cations are typically found on the left side of the periodic table (Alkali metals/Alkaline earth metals -groups 1&2) Anions are found on the right side (Halogens/Chalcogens - groups 16&17) Note that towards the middle of these two groups the lines get more blurry and you start seeing element...
Fri Nov 13, 2020 10:15 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: Textbook Problem 3f.5
Replies: 2
Views: 36

### Textbook Problem 3f.5

Can someone explain the reasonings for part b and c?

3F.5 Suggest, giving reasons, which substance in each of the following pairs is likely to have the higher normal melting point (Lewis structures may help your arguments): (b.) C2H5OC2H5(diethyl ether) or C4H9OH (butanol) (c.) CHI3 or CHF3
Tue Nov 10, 2020 12:19 pm
Forum: Ionic & Covalent Bonds
Topic: Textbook Problem 2d.3
Replies: 2
Views: 13

### Textbook Problem 2d.3

Can someone explain why the answer is (b)? 2D.3 Which of these compounds has bonds that are primarily ionic? (a) BBr3; (b) BaBr2; (c) BeBr2. I understand why its not Boron, but I don't know how we are supposed to know which will create to a more ionic bond (between Be and Ba) if we aren't given the ...
Fri Nov 06, 2020 7:42 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent bond character
Replies: 3
Views: 34

### Re: Covalent bond character

There is no correct image representation of what electrons look like. However, by distorted he means that the paths of the electrons are shifted so that they are less "circular" you could say, and more like an egg because the positive pull of the cation will attract electrons to create an ...
Fri Nov 06, 2020 7:40 pm
Forum: Ionic & Covalent Bonds
Topic: Problem 2A.23
Replies: 4
Views: 45

### Problem 2A.23

Can someone explain why part c is the answer that it is:

2A.23 On the basis of the expected charges on the monatomic ions, give the chemical formula of each of the following compounds: (c) aluminum hydride

Thu Nov 05, 2020 9:09 pm
Forum: Lewis Structures
Topic: writing molecular formulas
Replies: 4
Views: 53

### Re: writing molecular formulas

I also was wondering this, I'm pretty sure from what I keep hearing from others (who have gone to Lavelle's Office Hours) is that he will give us the formulas for things that we wouldn't typically know. But I'm also not sure if soon he would expect us to know formulas such as nitrate because they ar...
Wed Nov 04, 2020 3:24 pm
Forum: Trends in The Periodic Table
Topic: Nuclear Charge
Replies: 6
Views: 30

### Re: Nuclear Charge

Because as you go across a period you are not only just increasing in electrons you are increasing in protons. The positive central charge of the nucleus is becoming very big. As a result, the electrons in that outer shell will be pulled closer to the center due to the positive-negative attractions ...
Wed Nov 04, 2020 3:22 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic v. Covalent Bonds`
Replies: 10
Views: 59

### Re: Ionic v. Covalent Bonds`

Ionic bonds typically occur between a metal and a non-metal. One atom "donates" or "loses" electrons and the other atom snatches them up and completes the bond. In covalent bonds the electrons are shared amongst the atoms involved.
Thu Oct 29, 2020 7:55 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configurations
Replies: 15
Views: 93

### Re: Electron Configurations

I feel like I remember him saying it's useful to write it the long way because its more specific but its also not wrong to write it the shorter way. I think he will be explicit on whether it needs to be in the long form on midterms. Also I doubt he will ask us write out the ml quantum numbers for d ...
Thu Oct 29, 2020 7:47 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Shells, Subshells, and Orbitals
Replies: 2
Views: 43

### Shells, Subshells, and Orbitals

I have a decent understanding of the three terms: shells, subshells, and orbitals but I have a lot of trouble visualizing the complete relationships between them all for the periodic table and for atoms. I know that these are just models and we don't know what things look like but is there any way o...
Thu Oct 29, 2020 7:43 pm
Forum: Quantum Numbers and The H-Atom
Topic: Rydberg constant
Replies: 7
Views: 78

### Re: Rydberg constant

I believe the Sapling explanation is using different units. To be safe for midterms and the final just use the number and units given on the equation sheet we are allowed to use.
Thu Oct 29, 2020 7:42 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: h vs. ħ?
Replies: 11
Views: 118

### Re: h vs. ħ?

ħ is just some chemistry technical term/jargon for h/2π. Thus when its (1/2)*ħ it equals the h/4π in the other equation. Also the equations should both have a greater than or equal to sign, so I don't know why there is a discrepancy there.
Mon Oct 26, 2020 9:29 pm
Forum: Quantum Numbers and The H-Atom
Topic: 4th quantum number
Replies: 8
Views: 45

### Re: 4th quantum number

The 4th quantum number is found by determining the spin of the electron. A spin up electron will have the quantum number +1/2 and a spin down electron will have the quantum number -1/2.
Fri Oct 23, 2020 4:25 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Angular Momentum Quantum number
Replies: 3
Views: 23

### Re: Angular Momentum Quantum number

Professor Lavelle mentioned in his lecture on Friday that technically there are math models for an angular momentum of 4 and above but there are no elements that are on the periodic table for which that would apply to.
Thu Oct 22, 2020 8:25 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Sapling Number 11
Replies: 1
Views: 30

### Re: Sapling Number 11

Ive worked out the problem here:
Thu Oct 22, 2020 8:06 pm
Forum: Significant Figures
Topic: Midterm
Replies: 9
Views: 116

### Re: Midterm

Not sure, but you should know which answer is correct if that's the case if you know all the sig-fig rules, Lavelle has a whole document dedicated to sig-figs and rounding on his website and I would definitely recommend that.
Thu Oct 22, 2020 8:04 pm
Forum: Student Social/Study Group
Topic: Midterm study
Replies: 5
Views: 43

### Re: Midterm study

I would definitely recommend doing the post-assessment modules as well as go over any textbook problems you struggled with. Also review the outlines of what we are expected to know on Lavelle's website.
Thu Oct 22, 2020 8:02 pm
Forum: SI Units, Unit Conversions
Topic: SI Conversions
Replies: 11
Views: 82

### Re: SI Conversions

I think you should be able to use the most common conversions such as km to m and kg to g as well as picometers and nanometers as they have been in many practice problems.
Sat Oct 17, 2020 3:44 pm
Forum: Properties of Light
Topic: "Intensity"
Replies: 20
Views: 133

### Re: "Intensity"

How I see it is that when talking about "intensity" with regard to the wave model of light, intensity refers to amplitude. When we talk about "intensity" with regards to the particle model of light, intensity refers to number of photons. So I like to think of there being two defi...
Sat Oct 17, 2020 3:40 pm
Forum: Administrative Questions and Class Announcements
Topic: More modules
Replies: 3
Views: 29

### Re: More modules

I completely agree, I thought they were very effective for review (because it covered the lectures again) and sometimes Prof. Lavelle would have different things to add to each lecture and that would be helpful to my understanding.
Sat Oct 17, 2020 3:38 pm
Forum: Limiting Reactant Calculations
Topic: Testing with a periodic table
Replies: 16
Views: 172

### Re: Testing with a periodic table

We will have to be careful if the exams are proctored. My friend told me that she studied super hard for an exam and while she was taking it she read out loud the questions to herself to better comprehend it. The instructor watching her thought that she was reading the questions out loud to a frien...
Thu Oct 15, 2020 10:58 am
Forum: Einstein Equation
Topic: Textbook Question 1A.3
Replies: 3
Views: 60

### Textbook Question 1A.3

Can someone explain what the letter c (the answer) means? Which of the following happens when the frequency of elec- tromagnetic radiation decreases? Explain your reasoning. (a) The speed of the radiation decreases. (b) The wavelength of the radiation decreases. (c) The extent of the change in the e...
Tue Oct 13, 2020 11:47 am
Forum: Photoelectric Effect
Topic: How to calculate the kinetic energy, energy and frequency? [ENDORSED]
Replies: 20
Views: 4574

### Re: How to calculate the kinetic energy, energy and frequency?[ENDORSED]

diegomartinez1F wrote:Mass of electron is given:

Me= 9.10938 x 10^-31 kg

Do we need to convert this to grams or can we keep it as kg?
Fri Oct 09, 2020 10:58 am
Forum: Significant Figures
Topic: Which number determines sig figs of the answer?
Replies: 26
Views: 179

### Re: Which number determines sig figs of the answer?

Typically in cases of chemistry you will have some type of multiplication or division in your problem and as a result you will just use the smallest amount of sig figs in the givens as the amount in your answer. (but follow the rules others have given above if your problem happens to only include ad...
Tue Oct 06, 2020 3:40 pm
Forum: Empirical & Molecular Formulas
Topic: Fundamentals F 13
Replies: 8
Views: 86

### Re: Fundamentals F 13

I'm not too sure, I remember Lavelle told us this class does not focus on memorization but he never specified on this topic. Generally this type of naming is easy because sometimes when the elements are both on the right side of the periodic table they follow as: prefix (di, tri, penta) element and ...
Tue Oct 06, 2020 3:31 pm
Forum: Empirical & Molecular Formulas
Topic: Emprical Formulas Ever Larger than Molecular? [ENDORSED]
Replies: 26
Views: 458

### Re: Emprical Formulas Ever Larger than Molecular?[ENDORSED]

No, The empirical formula should be the simplest ratio form of the molecular formula. If the empirical formula was larger than the molecular, the empirical formula must not be simplified to its simplest ratio.
Tue Oct 06, 2020 3:27 pm
Forum: Empirical & Molecular Formulas
Topic: Fundamentals F. 27
Replies: 1
Views: 65

### Fundamentals F. 27

Can someone help with this problem, I'm not sure where to start.

F. 27) A mixture of NaNO3 and Na2SO4 of mass 5.37 g contains 1.61 g of sodium. What is the percentage by mass of NaNO3 in the mixture?
Mon Oct 05, 2020 5:31 pm
Forum: Significant Figures
Topic: Molar Mass Sig Figs
Replies: 9
Views: 81

### Molar Mass Sig Figs

Does anyone know how many sig figs we should take from the molar masses on the periodic table for our homework and problems? Also which is preferred: rounding or truncating?

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