## Search found 61 matches

Sun Jan 17, 2021 3:44 am
Forum: Student Social/Study Group
Topic: Comfort Movies
Replies: 108
Views: 242

### Re: Comfort Movies

I don't know why but watching 90s romcoms always puts me in a good mood (especially Clueless). A more recent one is Brooklyn 99 and I find myself rewatching it whenever I need a break.
Sun Jan 17, 2021 3:42 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6E.1 Question
Replies: 1
Views: 18

### Re: 6E.1 Question

We went over this problem in my discussion section so I'll show it the way my TA did it. So H2SO4 is a polyprotic acid meaning that it can basically lose multiple protons (H+). So for instance, H2SO4 <--> H+ + HSO4- would be one deprotonation of the acid and this is the equation my TA used. You woul...
Sun Jan 17, 2021 3:38 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Hess's Law
Replies: 1
Views: 9

### Re: Hess's Law

Hess's law essentially states that the delta H for a reaction is the same whether it occurs by one step or a series of steps. What this means is that you can add the delta H's for multiple reactions together to get the overall delta H. For sapling, we did not necessarily use Hess's law. It was more ...
Sun Jan 17, 2021 3:34 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc vs. Q
Replies: 5
Views: 17

### Re: Kc vs. Q

Hello, I believe I may be getting my variables mixed up, but I was wondering if the equilibrium constant Kc and the reaction quotient referred to the same value? The Kc value is the ratio of the concentration of product(s) over the concentration of the reactant(s) AT EQUILIBRIUM. Kc is only for sit...
Sun Jan 17, 2021 3:30 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Box method
Replies: 4
Views: 22

### Re: ICE Box method

Hello, I am having a bit of difficulty understanding how to use the ice box and was wondering if someone could explain how I would use it in these chemical equilibrium problems? So an ice box is used for weak acids or bases that do not completely dissociate. There are three sections to consider: th...
Sun Jan 10, 2021 5:29 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Question on #19 from focus topic 3
Replies: 3
Views: 21

### Re: Question on #19 from focus topic 3

19. Calculate the reaction quotient, QC, from the following equilibrium data collected in a 3.00 L sealed reaction vessel for the reaction: AsH3 (g) ⇌ As (s) + H2 (g) AsH3 = 5.55 x 10-4 mol, As = 3.31 x 10-3 mol, H2 = 1.23 x 10-3 mol. I know this seems like an easy problem but for the life of me I ...
Sun Jan 10, 2021 5:24 pm
Forum: General Science Questions
Topic: material
Replies: 4
Views: 30

### Re: material

14A was teaching the fundamentals of chemistry and you need that as a basis for what is taught in 14B. Most of chemistry is building on past knowledge and content so what we learned in 14A will be making appearances in certain topics.
Sun Jan 10, 2021 5:22 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Focus topic 3 question 26
Replies: 2
Views: 21

### Re: Focus topic 3 question 26

Hi! I am wondering if there is a way to solve this kind of question without doing it the long way (aka using the quadratic formula): 26. A mixture initially consisting of 0.250 N2 (g) and 0.500 M H2 (g) reacts to form NH3 (g) which is 0.15 M NH3 (g) at equilibrium. Calculate the concentration of N2...
Sun Jan 10, 2021 5:18 pm
Forum: Ideal Gases
Topic: partial pressures
Replies: 14
Views: 62

### Re: partial pressures

What do partial pressures really mean? Why can they be converted to concentrations? I'm just not quite understanding what the term means. The pressure of a mixture of gases is the sum of the partial pressures of the different gases in the mixture. So we're basically saying that all the gases in the...
Sun Jan 10, 2021 5:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling week 1 #2
Replies: 3
Views: 24

### Re: Sapling week 1 #2

At a certain temperature, 0.780 mol SO3 is placed in a 1.50 L container. 2SO3(g)↽−−⇀2SO2(g)+O2(g) At equilibrium, 0.160 mol O2 is present. Calculate Kc Could someone walk me through how to solve this? Thank you! I keep getting the wrong answer. The first thing you should do is convert everything to...
Sun Jan 10, 2021 5:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Module Question 13
Replies: 2
Views: 9

### Re: Module Question 13

For this question we would use the equilibrium constant expression
K=[Br]^2/[Br2]
We are provided with K and [Br2] so all you need to do is plug them in and solve for [Br]. The answer should be C.
Tue Dec 15, 2020 11:07 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Oxidation State
Replies: 4
Views: 37

### Re: Oxidation State

You would find it the same way as a normal compound. Although transition metals can have more than one possible oxidation state, the formula will reflect the oxidation state it is in. For example, if you have FeCl3, then you would find that iron has a +3 oxidation state. Similarly, if you are given ...
Tue Dec 15, 2020 6:41 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8520
Views: 1471936

### Re: Post All Chemistry Jokes Here

what do you call a prisoner that makes jokes?
a silicon
Tue Dec 15, 2020 6:12 pm
Forum: Student Social/Study Group
Topic: Plans for Relaxing After Finals
Replies: 97
Views: 452

### Re: Plans for Relaxing After Finals

I’m probably going to sleep a lot and catch up on some reading and shows.
Tue Dec 15, 2020 6:10 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pka and acidity
Replies: 6
Views: 20

### Re: pka and acidity

pKa is a property of a compound that tells us how acidic it is. It determines how easily a proton can be removed. So a low pKa means that the proton is easily removable and. stronger acid. If the pKa is higher then the proton is not easily removable and the acid is weaker.
Tue Dec 15, 2020 5:53 pm
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 337
Views: 139583

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

Dear Dr. Lavelle,
Thank you so much for all your help this quarter with chem 14A! All the resources and time you put into this class and into helping us was so useful and let me excel in chem! I’m looking forward to taking chem 14b with you and hopeful for a great winter quarter!!
Fri Dec 04, 2020 9:26 pm
Forum: Amphoteric Compounds
Topic: 6A 17
Replies: 4
Views: 52

### Re: 6A 17

how would you figure out the answers for 6A 17 "6A.17 State whether the following oxides are acidic, basic, or amphoteric: (a) BaO; (b) SO3; (c) As2O3; (d) Bi2O3." what would the explanation be for each? So an easy way to look at it would be that nonmetal oxides (like SO3) are acidic, met...
Fri Dec 04, 2020 9:19 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordination number
Replies: 2
Views: 15

### Re: coordination number

hello, how does one find a coordination number? The coordination number is the number of atoms bonded to the atom. So here are some steps to finding it: 1. Identify the central atom in the chemical formula and this is usually a transition metal 2. Locate the atom, molecule, or ion nearest the centr...
Sun Nov 29, 2020 11:06 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Equatorial vs. Axial
Replies: 4
Views: 35

### Re: Equatorial vs. Axial

I think of equatorial as the equator line on a globe. It goes horizontally like on the x plane.
Axial is like an axes on a globe. It goes vertically on the Y plane.
Sun Nov 29, 2020 11:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polar v nonpolar molecules
Replies: 30
Views: 151

### Re: polar v nonpolar molecules

So an easy way to determine polarity is by seeing is the molecule is "balanced" or "lopsided". If it is a molecule like CCl4 where all the atoms surrounding the C are Cl, it is balanced and nonpolar. This is because the electronegativity between the Cl and C (the Cl-C bond) are t...
Sun Nov 29, 2020 11:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Equatorial and Axial
Replies: 2
Views: 8

### Re: Equatorial and Axial

The way I learned how to look at it was first to look at the 3D diagrams for all the basic shapes (tetrahedral, octahedral, etc). Once you see these, you can have a basic idea of where atoms will go and that can be used for all the variations like bent or trigonal pyramidal. Having the mental pictur...
Sun Nov 29, 2020 10:59 pm
Forum: Student Social/Study Group
Topic: How to study for class
Replies: 30
Views: 177

### Re: How to study for class

I use the textbook for textbook problems mostly. I learn better when someone is explaining it rather than reading, so if I get stuck, I'll watch a youtube video on it to clarify.
Sun Nov 29, 2020 10:58 pm
Forum: Student Social/Study Group
Topic: Chemistry Among Us
Replies: 43
Views: 431

### Re: Chemistry Among Us

Being close to purple might be safer since they have not been acting suspicious throughout the game but I would still be wary.
Sun Nov 29, 2020 10:52 pm
Forum: Student Social/Study Group
Topic: Tips for Staying Focused
Replies: 52
Views: 524

### Re: Tips for Staying Focused

Before COVID, I would usually go to a coffee shop or something similar to study but with COVID, I've had to adjust that. I usually do my work at night because no one's awake so it's quiet and no one comes into my room. I will study for a certain amount of time or do a certain amount of homework and ...
Sun Nov 29, 2020 10:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Delocalized Pi Bond
Replies: 3
Views: 36

### Re: Delocalized Pi Bond

Delocalized pi bonds can occur in resonance structures. A bond pair can seem to move between two different pairs of atoms which can be seen in the different resonance structures. They are considered delocalized because the pi bond found in the double bond is shared among the bonds and does not belon...
Sun Nov 22, 2020 9:54 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8520
Views: 1471936

### Re: Post All Chemistry Jokes Here

How do Mr. and Mrs. Claus introduce their son?

"This is Arsenic"

(arsenic - our son Nick)
Sun Nov 22, 2020 9:50 pm
Forum: Student Social/Study Group
Replies: 86
Views: 866

### Re: Big Sad: Midterm 2

I think this midterm was definitely a bit harder just because of the concepts required for it. There is more conceptual questions that can be asked and lewis structures are really easy to mess up. I was for sure more worried for this midterm than I was for the first one but at this point, I am just ...
Sun Nov 22, 2020 9:40 pm
Forum: Student Social/Study Group
Topic: Final Jitters
Replies: 226
Views: 35987

### Re: Final Jitters

Does anyone know how to calm down your anxieties before you take this final? Since having test anxiety can be very distracting while you're trying to study or even while you're taking the test itself. Open to any tips:) Honestly, one thing that might cause you more anxiety is if you keep trying to ...
Sun Nov 22, 2020 9:35 pm
Forum: Sigma & Pi Bonds
Topic: Sigma Bond Flexibility
Replies: 5
Views: 32

### Re: Sigma Bond Flexibility

Can anybody help explain to me why sigma bonds allow so much more flexibility than pi bonds? I still don't really understand how it allows the atoms to rotate Sigma bonds have "end to end" overlapping unlike pi bonds which have lateral overlap (where the sides overlap) single bond: https:...
Sun Nov 22, 2020 9:30 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi Bonds
Replies: 4
Views: 46

### Re: Sigma and Pi Bonds

Why can there only be one sigma bond between two atoms? Why does a double bond have to be a sigma bond and pi bond and then a triple bond a sigma bond and two pi bonds? There can only be one sigma bond between two atoms because of the way they overlap. When the orbitals from two atoms overlap end-t...
Fri Nov 13, 2020 10:14 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

So cation are ions that lose electrons and have a positive charge. These would usually show up in group 1-13 and would have formulas like Ca+2. For these atoms, the quickest way to become stable (or like the noble gases) is to give up electrons and have an overall positive charge. For anions, these ...
Fri Nov 13, 2020 10:02 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook Problem 1.E.25
Replies: 1
Views: 25

### Re: Textbook Problem 1.E.25

Hi! I was going over the homework for this section and I realized I don't really understand part b of this problem: Give the notation for the valence-shell configuration (including the outermost d-electrons) of (a) the alkali metals; (b) Group 15 elements; (c) Group 5 transition metals; (d) the “co...
Fri Nov 13, 2020 9:57 pm
Forum: Dipole Moments
Topic: 3F.5 Question
Replies: 2
Views: 20

### Re: 3F.5 Question

Hi everyone! I was wondering if you guys could help me on part (c) of this problem? I was a little confused by the answer because they used LDF when they compared the two molecules, and I was wondering why we wouldn't be able to use dipole-dipole in this situation? Problem 3F.5: Suggest, giving rea...
Fri Nov 13, 2020 9:34 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Valence electron numbers
Replies: 6
Views: 60

### Re: Valence electron numbers

I think that valence electrons are every electron after the noble gas, but do we include d electrons? In the textbook problems, it sometimes does and sometimes doesn't include the d electrons as the valence. For example, how many valence would Sb +3 have? It's electron configuration is 4d105s2, so ...
Fri Nov 13, 2020 9:12 pm
Forum: Lewis Structures
Topic: Bond Length
Replies: 3
Views: 19

### Re: Bond Length

Does [N3]- or HNNH have a longer bond length? For N2H2, there is one double bond and two single bonds. The single bonds are going to be longer than the double bond. For [N3]-, there are two double bonds, so they are going to be the same length. The bond lengths are going to be different between the...
Thu Nov 05, 2020 1:50 pm
Forum: General Science Questions
Replies: 30
Views: 344

I think Lavelle said he would be reviewing questions that a lot of people missed on M1 and M2 for the final but I am unsure if he is going to be reviewing them now.
Thu Nov 05, 2020 1:49 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge & Lewis Structures
Replies: 5
Views: 40

### Re: Formal Charge & Lewis Structures

We use formal charge to find the most stable lewis structure, but do we have to include all possible variations of the lewis structure (like we would with resonance)? Or can we just use the most stable structure? I think it depends on the question that is asked. Usually for formal charge questions,...
Thu Nov 05, 2020 1:46 pm
Forum: Student Social/Study Group
Topic: Studying Tips
Replies: 23
Views: 159

### Re: Studying Tips

I want to better my study habits for the final? What are some studying methods that have helped you guys? What do you try to avoid? I usually go through my notes first and see what I am weak at or need more clarification ( this is after I've watched all the lectures and modules). Once I find where ...
Thu Nov 05, 2020 1:43 pm
Forum: Student Social/Study Group
Topic: Test Anxiety
Replies: 62
Views: 348

### Re: Test Anxiety

I am not sure if anyone struggles with test anxiety... if you do, what are some techniques you guys use to deal and control test anxiety? Thank you. I try to calm my self first by just breathing because I find that they first thing that happens to me is that my breathing starts becoming weird and t...
Thu Nov 05, 2020 1:41 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Sapling Assigning Formal Charges
Replies: 4
Views: 43

### Re: Sapling Assigning Formal Charges

I am having trouble figuring out what charges to assign to each atom. I calculated the formal charge for each atom using the formula, but I kept getting the wrong answer. I think I may be using the formula wrong, for the amount of valence electrons of the atom would that be the amount assigned in t...
Fri Oct 30, 2020 10:37 pm
Forum: Trends in The Periodic Table
Topic: Ionization energy
Replies: 4
Views: 57

### Re: Ionization energy

Why does oxygen have a lower first ionization energy than both nitrogen and fluorine? How do we determine reasons for ionization energy differences? For ionization energy we have to look at orbital diagrams. Let's look at the 2p sublevel for each element. Nitrogen has all half filled orbitals which...
Fri Oct 30, 2020 10:32 pm
Forum: Trends in The Periodic Table
Topic: Electron-electron repulsion
Replies: 5
Views: 56

### Re: Electron-electron repulsion

A good way to think about electron-electron repulsion is with magnets. If you put two magnets together with the same ends facing each other, they repel. So if you tried to put the two negative ends together, they push against that and you can't really push them together. The same thing is happening ...
Fri Oct 30, 2020 10:29 pm
Forum: Student Social/Study Group
Topic: How to relax
Replies: 113
Views: 596

### Re: How to relax

I usually relax by watching a drama or listening to music. Recently, I've been playing Among Us more so I use that to relax as well. If I have a lot of time, I like to read (but that hasn't been happening much with school).
Fri Oct 30, 2020 10:27 pm
Forum: Photoelectric Effect
Topic: Sapling using de broglie's
Replies: 7
Views: 78

### Re: Sapling using de broglie's

So for this problem you would need to find the molar mass of Cl2 which is about 71 grams and then convert to kg which would be .071 kg. Once you convert from g to kg, you then need to convert to kg/molecule rather than keeping it in kg/mol. You would divide by Avogadro's number. This will put it in ...
Fri Oct 30, 2020 10:23 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Using quantum numbers to find number of electrons
Replies: 4
Views: 53

### Re: Using quantum numbers to find number of electrons

If you are given the quantum numbers for n, l, and m sub l, how would you go about finding the number of electrons in the atom? For example: n=7, l=2, m sub l=-1 For quantum numbers, I think you can use them to find the maximum number of electrons. Lets use the numbers 2, 1, 0, +1/2 First you would...
Fri Oct 30, 2020 10:10 pm
Forum: *Shrodinger Equation
Topic: New Audio-Visual Modules
Replies: 9
Views: 100

### Re: New Audio-Visual Modules

Personally, I liked the audio visual modules more than the lectures because I could understand them a little better. The lectures were good but the audio visual ones just helped me a little more.
Sat Oct 24, 2020 7:46 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Replies: 92
Views: 2095

I usually look through my notes first and see where my weak points are and maybe watch some videos on youtube as a supplement to give me more information. You could also read the textbook but I find that the textbook sometimes gives too much information and might be confusing. Then I would do practi...
Sat Oct 24, 2020 7:41 pm
Forum: Balancing Chemical Reactions
Topic: combustion
Replies: 4
Views: 55

### Re: combustion

Samin Kabir wrote:Why do we have to include the delta sign above the arrow on only combustion rxns?

Combustion reactants are where the main reactant is supposed to be like burned so the symbol "Δ" is often used to indicate that the reaction is to be heated.
Sat Oct 24, 2020 7:39 pm
Forum: Balancing Chemical Reactions
Topic: States of matter in chem equations
Replies: 13
Views: 115

### Re: States of matter in chem equations

Hello, When we have to balance chem equations do we have to include the states of matter in all components. Additionally how do we know what state of matter a reactant/product is in? I think Lavelle said that he would give us the states of matter of the reactants/products but I am not completely ce...
Sat Oct 24, 2020 7:37 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity and Electronegativity
Replies: 9
Views: 83

### Re: Electron Affinity and Electronegativity

Hi I'm still confused over the difference between electron affinity and electronegativity. Do they effectively go hand in hand? The electron affinity of an atom or molecule is defined as the amount of energy released when an electron is added to a neutral atom or molecule in the gaseous state to fo...
Sat Oct 24, 2020 7:36 pm
Forum: Properties of Electrons
Topic: Sapling #23
Replies: 4
Views: 41

### Re: Sapling #23

How do you find the electron affinity in kJ/mol? So first, you would convert the incident wavelength into energy using E= hv/lambda equation. This would be in E/photon. Then you would convert the 0.137 eV into Energy by multiplying it by 1.602x10^-19 J and it would become energy in joules. Subtract...
Wed Oct 14, 2020 9:21 pm
Forum: Properties of Electrons
Topic: The Nuclear Model of an Atom: e/m
Replies: 2
Views: 66

### Re: The Nuclear Model of an Atom: e/m

Hi! I was reading the textbook in Focus 1, and I saw that there was a ratio "e/m, the ratio of the magnitude of the electron’s charge e to its mass m." I am overall just really confused on the concept because of the values of e=1.602×10^−19 C and m=9.109×10^−31 kg. Can someone please expl...
Mon Oct 12, 2020 11:21 pm
Forum: Significant Figures
Topic: How to use Scientific Notation
Replies: 9
Views: 106

### Re: How to use Scientific Notation

When multiplying two numbers in scientific notation, multiply their coefficients and add their exponents. When dividing two numbers in scientific notation, divide their coefficients and subtract their exponents. If you remember from math where we were taught how to multiply and divide with exponents...
Mon Oct 12, 2020 11:18 pm
Forum: Properties of Electrons
Topic: Kinetic energy of electrons
Replies: 3
Views: 46

### Re: Kinetic energy of electrons

You would use the mass of an electron which is approximately 9.1093837015 x 10^-31 kg.
Mon Oct 12, 2020 11:12 pm
Forum: Properties of Electrons
Replies: 2
Views: 22

If you know the frequency of the UV radiation, you can use the equation E = hv, h being Planck's Constant 6.626 x 10^-34 Js. If all you know is the wavelength, you can use the equation frequency = (3.00 x 10^8) / wavelength, then use the energy equation above with the calculated frequency. Hope thi...
Mon Oct 12, 2020 11:10 pm
Forum: Properties of Light
Topic: Regions
Replies: 2
Views: 25

### Re: Regions

Usually in chemistry ( or at least that I have seen), we mainly focus on infrared, ultraviolet, and visible light. You can tell them apart by their wavelengths. Infrared light has the longest wavelengths of the three (700 nm to 1 mm), then visible lights (390 nm to 700 nm), and finally, ultraviolet ...
Mon Oct 05, 2020 2:42 pm
Forum: Molarity, Solutions, Dilutions
Topic: Units for Dilution Equation [ENDORSED]
Replies: 23
Views: 208

### Re: Units for Dilution Equation[ENDORSED]

No they are not. For the .987x10^-4, it should not be written this way because proper scientific notation would be 9.87x10^-5 because you have to move the decimal point over to the right by one so it would not be the same as 9.87x10^-3.

.987x10^-4 = .0000987

9.87x10^-3 = .00987
Mon Oct 05, 2020 2:37 pm
Forum: Empirical & Molecular Formulas
Topic: Fundamentals L. 39
Replies: 7
Views: 100

### Re: Fundamentals L. 39

So first I like to get all the information I need. When doing empirical formulas, you need the amount of the elements in the oxide which would be the tin and the oxygen. So you know that you have 1.50 g of tin which we can convert to grams using molar mass. To find the oxygen, we would have to subtr...
Mon Oct 05, 2020 2:31 pm
Forum: Limiting Reactant Calculations
Topic: Fundamentals M5
Replies: 7
Views: 82

### Re: Fundamentals M5

When doing these problems, instead of looking for the reactant in excess, try looking for the limiting reactant and the other one will be the one in excess. I find this to be an easier way of thinking about the problem.
Mon Oct 05, 2020 2:29 pm
Forum: Quantum Numbers and The H-Atom
Topic: Atomic Spectra Post-Module Assessment #29.
Replies: 2
Views: 47

### Re: Atomic Spectra Post-Module Assessment #29.

First we are going to use the E= (planck's constant x speed of light) / wavelength. You need to convert the wavelength from nm to m in order to use it. Using this formula, you should get energy per photon. Then once you get energy per photon, you are going to divide the total energy (11J) by the ene...
Mon Oct 05, 2020 2:06 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E3
Replies: 3
Views: 76

### Re: E3

What I did first was just work with what was given. So you know that there are 9 gallium atoms that are being used. You need to find how many astatine atom to use so that the masses on both sides are equal. First, I took the 9 gallium atoms and converted that to moles using Avagadro's constant and w...