## Search found 63 matches

Sun Jan 17, 2021 4:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reaction shift
Replies: 5
Views: 10

### Re: Reaction shift

The easiest way to do this is to look at what is being added to the reaction. If more of the product is being added to the reaction, you will subtract x from the products.
Sun Jan 17, 2021 4:35 pm
Forum: Ideal Gases
Topic: Equilibrium Constant (Q and K)
Replies: 13
Views: 41

### Re: Equilibrium Constant (Q and K)

Q is simply the concentrations of the molecules at any given time. It can be, but is not necessarily, equal to Q. Given enough time, Q should always reach K
Sun Jan 17, 2021 4:29 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Endothermic/exothermic reactions and K
Replies: 11
Views: 28

### Re: Endothermic/exothermic reactions and K

For endothermic reactions, K increases when temperature increases
For exothermic reactions, K decreases when temperature increases.
Sun Jan 17, 2021 4:23 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: How do we know a compound is a weak acid or base?
Replies: 6
Views: 22

### Re: How do we know a compound is a weak acid or base?

As many others have said, look at which one donates protons and which one accepts protons. There isn't a real way to determine if it is a strong acid/base except for just memorizing the lists of them.
Sun Jan 17, 2021 4:20 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Getting two positive x values when using quadratic
Replies: 43
Views: 157

### Re: Getting two positive x values when using quadratic

Yes, you want to test both positive values in order to see which one would fit in the ICE table
Sun Jan 10, 2021 4:35 pm
Forum: Ideal Gases
Topic: value of R
Replies: 24
Views: 75

### Re: value of R

You use the value of R that would cancel out the units of the pressure, volume, and temperature.
Sun Jan 10, 2021 4:27 pm
Forum: Ideal Gases
Topic: Difference between real and ideal gas
Replies: 10
Views: 75

### Re: Difference between real and ideal gas

As a follow-up question, if real and ideal gasses are so different than each other, why is it helpful to treat real gasses the same as ideal gasses? Would this assumption not cause problems?
Sun Jan 10, 2021 4:23 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Are there reactions that just do not/ can not ever reach equilibrium?
Replies: 18
Views: 61

### Re: Are there reactions that just do not/ can not ever reach equilibrium?

I did a little research and it would appear that the only way a reaction could not reach equilibrium, would be if the K value was incredibly small or incredibly large. For example, if the K value was something like K = 10^30, it would mean that there would be 10^30 molecules of the product for every...
Sun Jan 10, 2021 4:10 pm
Forum: Ideal Gases
Topic: Bars to atm [ENDORSED]
Replies: 31
Views: 164

### Re: Bars to atm[ENDORSED]

If we are assuming that 1 bar is equal to 1 atm, would we assume that the conversion would allow for infinite sig. figs?
Sun Jan 10, 2021 4:09 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Water
Replies: 28
Views: 92

### Re: Water

Does anybody mind posting an example of a reaction involving water, in which H2O would be included in the ICE table?
Sat Dec 12, 2020 6:19 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa greater than pH
Replies: 3
Views: 32

### Re: pKa greater than pH

In this situation, the acid will not dissociate, so the solution will remain neutral
Sat Dec 12, 2020 6:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles
Replies: 12
Views: 91

### Re: Bond angles

Yes, please make sure you know the bond angles. Here is a good reference image:
https://i.pinimg.com/originals/62/14/b5 ... 4ee088.jpg
Sat Dec 12, 2020 6:13 pm
Forum: Polyprotic Acids & Bases
Topic: Defintion
Replies: 24
Views: 764

### Re: Defintion

I think that the only polyprotic acids we need to know are:
H2SO4, H2CO3, and H3PO4
Sat Dec 12, 2020 6:11 pm
Forum: Amphoteric Compounds
Topic: Recognizing Amphoteric Substances
Replies: 8
Views: 67

### Re: Recognizing Amphoteric Substances

I don't really know how to figure out if a substance is amphoteric, but, I think that the only ones we need to know are:
BeO, Al2O3, Ga2O3, SaO2, Sb2O5, and PbO2.
Sat Dec 12, 2020 6:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electron Geometry
Replies: 8
Views: 54

### Re: Electron Geometry

Electron Geometry treats electron pairs as if they are bonded atoms.
i.e The electron geometry is the same for a molecule with the structure AX2E2 as it is for AX4
Sat Dec 12, 2020 6:06 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Calculating H+
Replies: 17
Views: 47

### Re: Calculating H+

In order to go from pH to H+, you would take the inverse log of the negative pH.
i.e 8.85 = -log(x) and solve for x
Sun Dec 06, 2020 2:16 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordination number
Replies: 13
Views: 80

### Re: coordination number

Coordination number is simply the number of the bonds connected to the transition metal cation.
Sun Dec 06, 2020 2:14 am
Forum: Properties of Light
Topic: Is c always the speed of light?
Replies: 88
Views: 457

### Re: Is c always the speed of light?

c is always the speed of light as long as it is in a vacuum. If it is the speed of light not it a vacuum, then it varies.
Sun Dec 06, 2020 2:10 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Sapling W9 #3
Replies: 6
Views: 55

### Re: Sapling W9 #3

I see people mentioning that planar shapes would never be ideal for 6 bond, because the electrons want to be as spread out from each other as possible. What number of bonds would be fine being in a planar shape?
Sun Dec 06, 2020 2:08 am
Forum: Coordinate Covalent Bonds
Topic: Coordinate Covalent Bonds and Covalent Bonds
Replies: 7
Views: 70

### Re: Coordinate Covalent Bonds and Covalent Bonds

A coordinate covalent bond is specifically when a transition metal cation bonds with anything that can donate electrons (these are called ligands).
Sun Dec 06, 2020 2:06 am
Forum: Resonance Structures
Topic: Stability
Replies: 13
Views: 107

### Re: Stability

They are more stable due to the delocalization of electrons. The energy of delocalized electrons is spread out over a larger area, making it more stable.
Sun Nov 29, 2020 8:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: H20 Shape
Replies: 17
Views: 102

### Re: H20 Shape

Because of the way lone pairs interact, the lone pairs would be closer to each other, while pushing away the two bonded atoms. Keep in mind that a square planar formation requires 4 bonded atoms and two lone pairs.
Sun Nov 29, 2020 12:27 pm
Forum: Lewis Structures
Topic: Molecular Shapes
Replies: 5
Views: 401

### Re: Molecular Shapes

https://i.pinimg.com/originals/62/14/b5 ... 4ee088.jpg
This chart has almost if not every single molecule shape with drawings and bond angles.
Sun Nov 29, 2020 12:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #3 Bond Angle
Replies: 8
Views: 72

### Re: Sapling #3 Bond Angle

The easiest way to know the bond angle is simply by memorizing it for each shape. I would recommend looking up tables that have all of the possible molecular geometries, and their corresponding bond angles
Sun Nov 29, 2020 12:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: homework question
Replies: 2
Views: 21

### Re: homework question

As to your first question, you bring up a really good point. I initially drew it all out linearly with double bonds connecting all the carbon atoms, and based on one of the questions that follow asking about the bonds connecting the carbon atoms it is clear that they would like us to draw it all wi...
Sun Nov 29, 2020 12:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Shape for C2H4
Replies: 3
Views: 14

### Re: VSEPR Shape for C2H4

Looking at the the lewis strucutre, it would appear C2H4 is indeed two trigonal planars.
Sun Nov 29, 2020 12:09 pm
Forum: Hybridization
Topic: sapling #11
Replies: 11
Views: 64

### Re: sapling #11

The general guideline for hybridization is as follows: Regions of e- density = number of hybrid orbitals 1 s-orbital + 1 p-orbital → 2 sp hybridized orbitals (Linear) 1 s-orbital + 2 p-orbitals → 3 sp2 hybridized orbitals (Trigonal planar) 1 s-orbital + 3 p-orbitals → 4 sp3 hybridized orbitals (Tetr...
Mon Nov 23, 2020 12:57 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angle tips
Replies: 10
Views: 64

### Re: bond angle tips

The way I learned the bond angles in high school, was by making a table that contained the names of molecules, drawings of them, and the bond angles. By studying this, it allowed me to later recall the drawing that contained the bond angles
Sun Nov 15, 2020 6:13 pm
Forum: Lewis Structures
Topic: Lewis acids and Bases
Replies: 20
Views: 119

### Re: Lewis acids and Bases

After drawing the lewis dot structure, there is an unfilled octet, then it is a lewis acid. If there is a lone pair, it is a lewis base.
Sun Nov 15, 2020 6:07 pm
Forum: Resonance Structures
Topic: bond length
Replies: 37
Views: 153

### Re: bond length

I do not believe that we are expected to calculate bond length. BUT, it is important to know trends for bond length. Know that bond length is inversely proportional to bond strength. Also make sure to remember that the larger an atom is, the larger the bond length will be.
Sun Nov 15, 2020 6:04 pm
Forum: Dipole Moments
Topic: Do london dispersion forces occur for polar molecules
Replies: 3
Views: 23

### Re: Do london dispersion forces occur for polar molecules

LDF should be present in all molecules, polar and non-polar. This is because LDF are a sort of pure chance thing, where electrons just end up on one side of a molecule more than the other
Sun Nov 15, 2020 6:02 pm
Forum: Octet Exceptions
Topic: Octet Rule Exceptions
Replies: 20
Views: 170

### Re: Octet Rule Exceptions

Sulfur and Chlorine are the only two exceptions I believed you did not mention. Like Phosphorus, these are able to accommodate more than 8 valence e-. This is due to the 3d block being able to be used to store extra electrons
Sun Nov 15, 2020 6:00 pm
Forum: Dipole Moments
Topic: Rod-shaped molecules
Replies: 6
Views: 52

### Re: Rod-shaped molecules

For a rod shaped model, the two molecules are much closer together, sharing a much greater surface area. With this, electrons are much closer together, making dipole moments all the more common.
Sun Nov 15, 2020 5:58 pm
Forum: Bond Lengths & Energies
Topic: Hydrogen Bonding
Replies: 13
Views: 68

### Re: Hydrogen Bonding

From what I understand there are no exceptions. Hydrogen bonding can occur when ONLY N, O, and F are present. If they are not present, there can not be hydrogen bonding
Sun Nov 08, 2020 7:37 pm
Forum: Administrative Questions and Class Announcements
Topic: How to list Chem_Mod posts
Replies: 19
Views: 40443

### Re: How to list Chem_Mod posts

Is Chem_Mod Dr. Lavelle? Or is it a shared account between Lavelle and TA's? Anyways thanks for the info!
Sun Nov 08, 2020 7:36 pm
Forum: Quantum Numbers and The H-Atom
Topic: Pauli Exclusion Principle and Hund's Rule
Replies: 4
Views: 15

### Re: Pauli Exclusion Principle and Hund's Rule

I see others explaining the two concepts thoroughly, so I will just hijack this thread in order to share a little tip for remembering Hund's rule from my old chem teacher. Hund's is for heaven. What she meant by this is that, electrons fill up separate orbitals in the same subshell, with parallel sp...
Sun Nov 08, 2020 7:31 pm
Forum: Ionic & Covalent Bonds
Topic: London dispersion forces
Replies: 12
Views: 55

### Re: London dispersion forces

From what I understand, London dispersion forces are when, through random chance, electrons end up being on one side of the compound more than the other. This causes one end of the compound to be more negative, while the other end is more positive.
Sun Nov 08, 2020 7:29 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 Question Count
Replies: 17
Views: 106

### Re: Midterm 2 Question Count

As a follow-up question, do we know how much material is covered/when midterm 2 is?
Sun Nov 08, 2020 7:28 pm
Forum: Coordinate Covalent Bonds
Topic: Definition
Replies: 17
Views: 236

### Re: Definition

After reading some on the replies, I would like to ask the follow-up question: How can we know if a compound receives its needed electrons solely from another compound?
Sun Nov 08, 2020 7:25 pm
Forum: Student Social/Study Group
Topic: Mid-quarter Check in
Replies: 67
Views: 281

### Re: Mid-quarter Check in

So far I have kept my head above the water, but man this quarter is a ton of work. It feels like the only thing I do is work all day. But besides that, Chemistry class itself is going pretty well!
Sat Oct 31, 2020 8:56 pm
Forum: Trends in The Periodic Table
Replies: 2
Views: 21

^^^^^
The reason why the effect going across a row has such a lower effect on the decrease of the atomic radii is because of the electron shielding's limited effect. Increasing radii through gaining new shells is much greater of an effect.
Sat Oct 31, 2020 8:51 pm
Forum: Photoelectric Effect
Topic: Lyman Series
Replies: 30
Views: 199

### Re: Lyman Series

You would only assume this if the it was an emission spectrum problem. If it was an absorption problem, you would assume that n=1 is the initial.
Sat Oct 31, 2020 8:35 pm
Forum: Student Social/Study Group
Topic: Halloween!!!
Replies: 54
Views: 332

### Halloween!!!

Happy Halloween Everybody!!!
I thought it would be fun if everybody listed the things they were doing/did for Halloween. I dressed up with some siblings and watched the ring. We also ordered some sushi. What has everyone else done for Halloween?
Sat Oct 31, 2020 8:26 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 7
Views: 218

### Re: Drawing Lewis Structures

As a good rule of thumb, it is best to put the atom that has the least electronegativity in the center.
Sat Oct 31, 2020 8:24 pm
Forum: Ionic & Covalent Bonds
Topic: Homework due date
Replies: 49
Views: 336

### Re: Homework due date

I was wondering the same thing but, for now I would say to just try and get it done before then
Sat Oct 31, 2020 8:18 pm
Forum: Student Social/Study Group
Topic: Favorite TV shows
Replies: 178
Views: 879

### Re: Favorite TV shows

To try and recommend shows with scientific themes, Dr. Stone is a great show involving someone trying to rebuild society with science. There are numerous occasions in the show where the main character uses accurate chemistry in order to accomplish this. I highly recommend this show.
Sat Oct 24, 2020 10:56 pm
Forum: Properties of Light
Topic: Sapling Randomized Questions
Replies: 5
Views: 35

### Re: Sapling Randomized Questions

The questions appeared to be in the correct order when I completed them a few nights ago.
Sat Oct 24, 2020 10:53 pm
Forum: Administrative Questions and Class Announcements
Topic: Printouts for Midterm
Replies: 8
Views: 69

### Re: Printouts for Midterm

I am fairly certain that the only things you are allowed to have are the periodic table and the approved list of formulas, both of which can be found on Lavelle's website.
Sat Oct 24, 2020 10:49 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg’s Constant
Replies: 6
Views: 80

### Re: Rydberg’s Constant

To add on to what everyone else is saying, you know that n=1 is involved if it is a hydrogen atom emitting/absorbing UV rays. N=2 is involved if it is in the visible light spectrum.
Sat Oct 24, 2020 10:39 pm
Forum: Student Social/Study Group
Topic: Midterm scratch paper
Replies: 9
Views: 50

### Re: Midterm scratch paper

From what I understood from my TA, the only thing that is graded is the test itself. Because of this, we can assume that no work needs to be shown. (I would definitely recommend you write the work down though, as it is easy to get lost in the problem without it.)
Sat Oct 24, 2020 10:38 pm
Forum: Student Social/Study Group
Topic: How to relax
Replies: 115
Views: 600

### Re: How to relax

Whenever I am feeling stressed out from class, I normally relax with a nice cup of coffee and a snack. No matter how stressed I was before, this always helps me chill out for at least a few minutes.
Sat Oct 24, 2020 10:36 pm
Forum: Einstein Equation
Topic: Textbook Problem 1A.3
Replies: 9
Views: 55

### Re: Textbook Problem 1A.3

I am fairly certain that there is no relationship between the frequency/wavelength of electromagnetic radiation, and the speed at which it moves. This is because electromagnetic radiation moves at a constant speed of 3.0 x 10^8 m/s in a vacuum. This is how we get the formula c= wavelength * frequency.
Sat Oct 17, 2020 5:54 pm
Forum: Einstein Equation
Topic: Planck's Number
Replies: 6
Views: 108

### Re: Planck's Number

To add on to what everyone else in the thread has already stated, planck's constant is used to relate the frequency of a wave to the energy of a photon. It was calculated by measuring the relationship between the two. It turned out that the frequency and the energy of the photon were directly propor...
Sat Oct 17, 2020 5:48 pm
Forum: Administrative Questions and Class Announcements
Topic: Calculator?
Replies: 9
Views: 104

### Re: Calculator?

DanielHong2L wrote:If I remember correctly, according to my TA and other folks, TI 84's can be used during exams.

Nice! Thanks for the quick response. I will update this thread later if I get confirmation from my own TA.
Sat Oct 17, 2020 5:47 pm
Forum: Photoelectric Effect
Topic: Textbook Problem 1A9
Replies: 4
Views: 35

### Re: Textbook Problem 1A9

I will try and give a decent explanation on how to solve this problem. The first step of is to analyze exactly what electromagnetic waves this college student would be running in to throughout the day. When reading, the student encounters visible light waves When at the dentist, X-rays When microwav...
Sat Oct 17, 2020 5:32 pm
Forum: Student Social/Study Group
Topic: How are you studying?
Replies: 203
Views: 1293

### Re: How are you studying?

My strategy has been to watch lecture and take notes. Afterwards, I watch the audio-visual focus topics and take the post assessments. If I feel like I need some more practice, I try and do some of the recommended book problems
Sat Oct 17, 2020 5:27 pm
Forum: Properties of Electrons
Topic: Work function/Threshold Energy
Replies: 19
Views: 91

### Re: Work function/Threshold Energy

On that note, does threshold energy refer to the amount of energy needed to move the electron in general or does it differ depending on the level level? All the threshold energy refers to is the energy required to dislocate an electron from an atom of any metal. If the energy of the photon was the ...
Sat Oct 17, 2020 5:14 pm
Forum: Administrative Questions and Class Announcements
Topic: Calculator?
Replies: 9
Views: 104

### Calculator?

It seems that we are unable to use calculators that can use text. This would lead me to believe that I could not use my handy dandy TI-84 calculator. Anybody have any ideas on some chemistry approved calculators?
Fri Oct 09, 2020 10:32 pm
Forum: Administrative Questions and Class Announcements
Topic: Petition to Bring Music Back To Lectures [ENDORSED]
Replies: 34
Views: 541

### Re: Petition to Bring Music Back To Lectures[ENDORSED]

It is very clear that everyone in this thread would love for the music to return; I would agree. In the event that the music does not return, I would love to know if anybody knows the name of this amazing track. I would love to listen to it before every lecture, just so I can get hyped to learn some...
Fri Oct 09, 2020 10:25 pm
Forum: SI Units, Unit Conversions
Topic: How to Show Your Work
Replies: 16
Views: 144

### Re: How to Show Your Work

While showing work is not necessary, I would highly recommend showing work. Showing work allows you to not get lost in the numbers as easily, and it can also help you understand exactly what you are doing. At the very least, you should probably show work with regards to dimensional analysis. I have ...
Fri Oct 09, 2020 10:22 pm
Forum: Student Social/Study Group
Topic: Regarding Quizzes
Replies: 5
Views: 48

### Re: Regarding Quizzes

I received an email from my TA mentioning HW and Quizzes being taken using a special program, but I think the quiz part was a typo? I could not find anywhere on the syllabus that mentioned any quizzes, so I am fairly certain that there are no quizzes.
Fri Oct 09, 2020 10:17 pm
Forum: Administrative Questions and Class Announcements
Topic: What's the best way to study?
Replies: 7
Views: 65

### Re: What's the best way to study?

I've noticed that the textbook problems are significantly more difficult than the examples given during the lecture and even the problems in the sapling homework. So to study for tests would it be beneficial to do more textbook problems? Or should I just review the lectures? Thank you! After doing ...
Wed Oct 07, 2020 12:38 am
Forum: Significant Figures
Topic: All students read this sig fig post [ENDORSED]
Replies: 133
Views: 17981

### Re: All students read this sig fig post[ENDORSED]

Do you know if the problems will specifically tell us how many significant figures to use? First time using this forum so I have no idea if I am doing it right, but to try and answer your question: It is highly unlikely that any problems will specify how many significant figures to use in the answe...