Search found 64 matches

Thu Jan 21, 2021 8:47 pm
Forum: Phase Changes & Related Calculations
Topic: Heat and temperature change
Replies: 5
Views: 10

Re: Heat and temperature change

the temperature doesn't rise during a phase change because the energy goes towards altering the molecules and changing the phase. once the phase changes the temperature increases until the substance changes phases again.
Thu Jan 21, 2021 8:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong acids & bases
Replies: 4
Views: 19

Re: Strong acids & bases

their equilibrium constants are just very large because the acid/base almost completely dissociates
Thu Jan 21, 2021 8:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Buffers?
Replies: 2
Views: 9

Re: Buffers?

I would wait for professor lavelle to mention it lecture
Sat Jan 16, 2021 6:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw constant
Replies: 25
Views: 50

Re: Kw constant

H2O is in excess so the change in concentration would be negligible. if we were to add it into Kw it would be in the numerator and denominator, and therefore would cancel out.
Sat Jan 16, 2021 6:43 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 19
Views: 99

Re: Le Chatelier's Principle

basically it says that if there is a change in the system the chemical reaction will "shift" to go back to equilibrium and minimize the effects of that change
Sat Jan 16, 2021 6:42 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Using the ICE table
Replies: 32
Views: 79

Re: Using the ICE table

yes! an ICE table can be used for both partial pressures and concentrations.
Fri Jan 15, 2021 2:33 pm
Forum: General Science Questions
Topic: Calculating Ka from pKa
Replies: 7
Views: 29

Re: Calculating Ka from pKa

to find Ka from pKa you would do 10^(-pKa)
Fri Jan 15, 2021 2:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Finding pH for salts
Replies: 2
Views: 26

Finding pH for salts

How would we find the pH of a salt if both the cation and anion affect the pH of the solution?
Tue Jan 12, 2021 5:50 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction Quotient
Replies: 10
Views: 465

Re: Reaction Quotient

Q uses the concentration values we currently have, but K uses the equilibrium concentrations
Tue Jan 12, 2021 5:48 pm
Forum: Administrative Questions and Class Announcements
Topic: UA Workshops
Replies: 6
Views: 37

Re: UA Workshops

all the worksheets are different for every UA. go to as many as you can they are so so so helpful!!
Tue Jan 12, 2021 5:46 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw= 1.0 x 10^-14
Replies: 11
Views: 60

Re: Kw= 1.0 x 10^-14

as everyone said above Kw was experimentally determined
Tue Jan 12, 2021 5:43 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Bars
Replies: 8
Views: 33

Re: Bars

yes 1 bar is approximately 1 atm so we say that 1atm=1bar
Thu Jan 07, 2021 5:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE tables
Replies: 11
Views: 66

Re: ICE tables

I is initial concentrations, C is change in concentrations, and E is concentrations at equilibrium. Depending on what information we're given, we can use ICE tables to find the K value, or concentrations at equilibrium (if we already know the K value).
Thu Jan 07, 2021 5:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: change in pressure
Replies: 8
Views: 57

Re: change in pressure

if both sides of the equation have the same number of moles, a change in pressure will not affect equilibrium
Thu Jan 07, 2021 5:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #4
Replies: 5
Views: 59

Sapling #4

Problem 4 says: At a certain temperature, the given reaction has an equilibrium constant of Kp=341

PCl3(g)+Cl2(g)↽−−⇀PCl5(g)

PCl5 is placed in a sealed container at an initial pressure of 0.0220 bar. What is the total pressure at equilibrium?

Can someone explain how to solve this?
Thu Jan 07, 2021 4:53 pm
Forum: Ideal Gases
Topic: Reaction Quotient(Q) vs. Equilibrium Constant(K)
Replies: 9
Views: 63

Re: Reaction Quotient(Q) vs. Equilibrium Constant(K)

Q is at any point in the reaction but K is at equilibrium. comparing Q and K can tell you that the reaction is at equilibrium, or whether the reaction will shift to the right or the left to reach equilibrium
Thu Jan 07, 2021 4:52 pm
Forum: General Science Questions
Topic: mole vs. M
Replies: 16
Views: 106

Re: mole vs. M

M is concentration in mol/L. moles will be expressed as mol or mole
Tue Dec 15, 2020 7:36 pm
Forum: Amphoteric Compounds
Topic: Amphoteric vs Amphiprotic
Replies: 7
Views: 44

Amphoteric vs Amphiprotic

What's the difference between amphoteric and amphiprotic?
Sun Dec 06, 2020 5:49 pm
Forum: Hybridization
Replies: 7
Views: 54

omg thank you! this is so so so helpful <3
Sun Dec 06, 2020 5:09 pm
Forum: Amphoteric Compounds
Topic: Sapling HW #2 [ENDORSED]
Replies: 4
Views: 72

Sapling HW #2[ENDORSED]

Can someone explain how to determine which substance is amphoteric? Here's the question:

Which of these substances is amphoteric, that is, it can act as a Brønsted acid and a Brønsted base?

BrO2^-
H3PO4
HBrO2
PO4^3-
H2PO4^-
Sun Dec 06, 2020 11:40 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Flashcards
Replies: 8
Views: 63

Re: Flashcards

flashcards are super super helpful when trying to memorize names, or just learning the concepts. i would definitely say use flashcards for learning the different shapes of compounds, and naming compounds.
Sun Dec 06, 2020 11:39 am
Forum: Naming
Topic: Naming Coordination Compounds
Replies: 9
Views: 74

Naming Coordination Compounds

When do we add -ate to the end of the metal name?
Sun Dec 06, 2020 11:37 am
Forum: Lewis Acids & Bases
Topic: Acids question
Replies: 4
Views: 31

Acids question

When would we use the equation Ka= [A-][H+]/[AH]?
Sun Nov 29, 2020 5:51 pm
Forum: Lewis Structures
Topic: Sapling Week 7/8 #12
Replies: 8
Views: 58

Re: Sapling Week 7/8 #12

hi so you would use the mass percentages and assuming that you have a 100 gram sample we would have 37.5 g C, 12.6 g H, and 49.9 g O. Convert these to moles and find the molecular formula. This will be the formula used to draw the lewis structure and determine the hybridization
Sun Nov 29, 2020 5:47 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelates General Question
Replies: 2
Views: 24

Re: Chelates General Question

from my understanding a chelate contains a ligand that forms a ring of atoms that includes a central metal atom. i'm not completely sure why chelates form so if you know please let us know lol :)
Sun Nov 29, 2020 5:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: #13 Sapling Week 8
Replies: 18
Views: 100

Re: #13 Sapling Week 8

since each carbon atom has 4 regions of electron density (4 bonds) the shape is tetrahedral
Sun Nov 29, 2020 5:36 pm
Forum: Limiting Reactant Calculations
Topic: Cl vs Cl2
Replies: 9
Views: 90

Re: Cl vs Cl2

Yes! chlorine gas is a diatomic molecule and therefore chlorine gas is Cl2
Sat Nov 28, 2020 4:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Delocalized Pi Bond
Replies: 5
Views: 17

Delocalized Pi Bond

What is a delocalized pi bond?
Sun Nov 22, 2020 7:12 pm
Forum: Lewis Structures
Topic: Central Atom Question
Replies: 20
Views: 135

Re: Central Atom Question

As Dr. Lavelle has mentioned in lecture, H can never be the central atom because it can only have 1 bond
Sun Nov 22, 2020 7:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Question About Seesaw Molecular Geometry
Replies: 3
Views: 26

Re: Question About Seesaw Molecular Geometry

having the lone pair in the equatorial plane is more favorable because it only interacts with 2 bonds at 90 degrees. if it was on the axial plane it would interact w/ three atoms.
Sun Nov 22, 2020 7:06 pm
Forum: Lewis Structures
Topic: Focus 2 Exercise 7
Replies: 3
Views: 40

Re: Focus 2 Exercise 7

For a structure like this it's more trying different things and seeing which works. I had some trouble on this too but you just have to take different approaches and see which gives you the most stable and correct structure. there are multiple ways to do it
Sun Nov 22, 2020 7:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape of XeF2
Replies: 2
Views: 22

Shape of XeF2

How does XeF2 have a linear shape if it has 3 lone pairs?
Sun Nov 22, 2020 6:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling HW #3
Replies: 3
Views: 48

Sapling HW #3

Question 3 says: A Lewis structure is a two-dimensional representation of a molecule that does not necessarily show what shape that molecule would take in three dimensions. Based on the Lewis structure and your knowledge of VSEPR theory, approximate the smallest bond angle in this molecule. I'm not ...
Sun Nov 15, 2020 6:27 pm
Forum: Ionic & Covalent Bonds
Topic: Hydrogen Bonding
Replies: 13
Views: 65

Hydrogen Bonding

What specific characteristic do N, O, and F have that allow them to hydrogen bond with H? Is it just because they are highly electronegative?
Sun Nov 15, 2020 6:23 pm
Forum: Administrative Questions and Class Announcements
Topic: Electronegativity chart for Midterm
Replies: 7
Views: 68

Re: Electronegativity chart for Midterm

Hmmmm I'm not 100% sure but I think if we had to use electronegativity values, they would be given in the problem. To my understanding there isn't a chart we should print out but if I'm wrong pls correct me :)
Sun Nov 15, 2020 6:21 pm
Forum: Ionic & Covalent Bonds
Topic: Difference on how atomic size affects covalent and dipole interactions
Replies: 9
Views: 43

Re: Difference on how atomic size affects covalent and dipole interactions

yes, a greater atomic radius in LDF makes it more polarizable. In terms of ionic bonds, this means that the bigger the radius of the anion, the easier it is for it to be distorted, which gives it some covalent characteristics
Sun Nov 15, 2020 6:09 pm
Forum: Bond Lengths & Energies
Topic: Textbook question
Replies: 3
Views: 21

Re: Textbook question

Since AsF3 is polar, the bonds are stronger meaning it would require more energy to break the bonds. Therefore it would require a greater melting point compared to a non polar molecule like AsF5
Thu Nov 12, 2020 9:22 pm
Forum: Ionic & Covalent Bonds
Topic: Sapling HW Question 13
Replies: 3
Views: 32

Sapling HW Question 13

Hi can someone explain how to do this problem? I can't seem to get the correct answer. Urea is an organic compound widely used as a fertilizer. Its solubility in water allows it to be made into aqueous fertilizer solutions and applied to crops in a spray. What is the maximum theoretical number of wa...
Sun Nov 08, 2020 2:38 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and Lewis Structures
Replies: 10
Views: 72

Re: Formal Charge and Lewis Structures

I think finding the formal charges will make it easier to determine if your structure is the most stable form.
Sat Nov 07, 2020 7:58 pm
Forum: Naming
Topic: Formulas based on names
Replies: 8
Views: 140

Re: Formulas based on names

yeah I would say to just learn the rules for naming the really common formulas. that would really help you during exams and practice problems
Thu Nov 05, 2020 5:21 pm
Forum: Lewis Structures
Topic: Formal Charge
Replies: 5
Views: 28

Formal Charge

Is the structure more stable when the formal charges add up to 0, or if they add up to the net charge?
Thu Nov 05, 2020 5:14 pm
Forum: Lewis Structures
Topic: Sapling Homework Problem
Replies: 5
Views: 41

Re: Sapling Homework Problem

lewis acids accept electrons while lewis bases donate electrons
Thu Nov 05, 2020 11:58 am
Forum: Lewis Structures
Topic: Sapling HW Question 3
Replies: 5
Views: 52

Sapling HW Question 3

Hi could someone explain how to draw the lewis structure for the phosphite ion? I keep getting it wrong and I'm not sure why
Sun Nov 01, 2020 12:46 pm
Forum: Photoelectric Effect
Topic: Sampling Hw #19
Replies: 2
Views: 34

Re: Sampling Hw #19

Hi so the only equation you would need is lambda= h/m x v. For each of the particles given all the values stay the same except their masses. So to find velocity I would reorganize the equation to equal v, v=h/m x lambda. Then the only value that would change based on the particle is the mass, and th...
Sun Nov 01, 2020 12:39 pm
Forum: Quantum Numbers and The H-Atom
Topic: when n=5 and l=4
Replies: 16
Views: 156

Re: when n=5 and l=4

If n=5, then l can theoretically equal 0,1,2,...,n-1
Sun Nov 01, 2020 12:36 pm
Forum: DeBroglie Equation
Topic: Sapling HW Question 25
Replies: 8
Views: 83

Sapling HW Question 25

Hi I can't figure out how to solve the second part to this problem. The problem says: The E. coli bacterium is about 1.7 μm long. Suppose you want to study it using photons of that wavelength or electrons having that de Broglie wavelength. What is the energy E photon of the photon? What is the energ...
Sun Nov 01, 2020 12:09 pm
Forum: Quantum Numbers and The H-Atom
Topic: ml in quantum numbers
Replies: 3
Views: 34

Re: ml in quantum numbers

Hi ml is referring to the orientation of the angular momentum, (like px, py, pz). Each orientation also refers to an orbital in a subshell. For example, px may refer to the first orbital of the p block. This relates to the spin of an electron because since there are two electrons in each orbital, ea...
Sun Nov 01, 2020 11:58 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: N levels for electron configurations
Replies: 6
Views: 45

Re: N levels for electron configurations

Yes as everyone said above l correlates to the subshell. if l=1, then we are in the p subshell
Sun Oct 25, 2020 8:54 pm
Forum: Properties of Light
Topic: Amplitude
Replies: 9
Views: 64

Re: Amplitude

yes amplitude is only used in the wave model. when light acts like a photon amplitude does not increase the energy. the only way to increase energy would be to increase frequency.
Sun Oct 25, 2020 5:17 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E.23 Part A and C
Replies: 4
Views: 61

Re: E.23 Part A and C

I'm pretty sure part A is CuBr2, but either way Megan's steps are correct. If you follow the same steps for part c, (make sure to convert kg of UF6 to g), you should get 430. mol F^- as your answer
Sun Oct 25, 2020 4:57 pm
Forum: Properties of Light
Topic: Balmer or Lyman Series
Replies: 9
Views: 50

Re: Balmer or Lyman Series

The Lyman Series ends in n=1 and the Balmer Series ends in n=2. Also, the Lyman Series emits UV light because the gap between n=2 and n=1 is really big. Balmer series emit visible light. So if the problem says that UV light is emitted, you know that it's a Lyman series and that n final= 1. Hope that...
Sat Oct 24, 2020 9:47 pm
Forum: DeBroglie Equation
Topic: Advice for Correct Units for Midterm
Replies: 8
Views: 81

Re: Advice for Correct Units for Midterm

yes!! i've noticed that i always make mistakes when i don't write my units throughout the problem. i always make sure to write my units even if it takes a little longer to solve the problem :)
Sat Oct 24, 2020 9:42 pm
Forum: Student Social/Study Group
Topic: Midterm Question
Replies: 9
Views: 45

Re: Midterm Question

Yes we will be given constants, equations, and the periodic table. There are two links Professor Lavelle's website with equations and the periodic table. I would highly recommend printing those out! For studying I would just focus on understanding the constants and equations and when to apply them.
Sun Oct 18, 2020 8:25 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr frequency condition
Replies: 5
Views: 44

Re: Bohr frequency condition

yes everyone above is correct. it's basically saying the delta E can be applied to the E=hv equation to solve for frequency.
Sun Oct 18, 2020 8:07 pm
Forum: Properties of Light
Topic: Work Function
Replies: 3
Views: 49

Re: Work Function

yes the work function is the threshold energy. to find the work function (if they don't already provide it) you would use the equation Ephoton - work function= kinetic energy
Fri Oct 16, 2020 2:22 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Lecture 7 Question [ENDORSED]
Replies: 4
Views: 76

Re: Lecture 7 Question[ENDORSED]

yes the analogy is a perfect example. the negative sign is to show that the electron is losing energy, but we change it to a positive to calculate for wavelength and frequency, etc. basically to prove the conservation of energy.
Wed Oct 14, 2020 9:25 pm
Forum: General Science Questions
Topic: Balancing equations
Replies: 17
Views: 156

Re: Balancing equations

yes i take similar approaches to everyone above. no matter which approach you take you should get the same answer. a chemical equation only has one correct balanced equation.
Wed Oct 14, 2020 9:21 pm
Topic: What is Black Body?
Replies: 35
Views: 565

Re: What is Black Body?

a black body is an object that emits/absorbs all frequencies of light. however, this is a theoretical concept because no such object exists.
Fri Oct 09, 2020 8:18 pm
Forum: Properties of Light
Topic: photoelectric effect
Replies: 5
Views: 74

Re: photoelectric effect

That is a great question. In the photoelectric experiment they observed that increasing the intensity of the light did not eject electrons and they concluded that light was not acting like a wave. Instead it was acting like it was made of individual photons, where the individual photon's energy mus...
Thu Oct 08, 2020 10:02 pm
Forum: SI Units, Unit Conversions
Topic: Mole ratios: Don't forget them; how to convert g of one compound to g to an another compound/element.
Replies: 4
Views: 67

Re: Mole ratios: Don't forget them; how to convert g of one compound to g to an another compound/element.

Yes! This is a super important concept to understand when trying to find the amount of product produced. This is why knowing how to balance an equation and converting between mols and grams is a key concept. Thanks for this great explanation.
Thu Oct 08, 2020 9:56 pm
Forum: SI Units, Unit Conversions
Topic: Acronym for prefixes
Replies: 7
Views: 86

Re: Acronym for prefixes

Thank you for these great acronyms! This will be super helpful when working with prefixes. :)
Thu Oct 08, 2020 9:19 pm
Forum: Molarity, Solutions, Dilutions
Topic: #25 on Molarity and Dilution of a Solution Post Assessment
Replies: 6
Views: 72

Re: #25 on Molarity and Dilution of a Solution Post Assessment

I did this post assessment module a few days ago but if I remember correctly I got it right using these steps: Convert the 5.00 g KMnO4 to mols using its molar mass (158.04g/mol) and you'll get 0.0316 mol. Then using the volume you're given, find the molarity of the solution. Make sure to change th...
Tue Oct 06, 2020 11:33 pm
Forum: Molarity, Solutions, Dilutions
Topic: #25 on Molarity and Dilution of a Solution Post Assessment
Replies: 6
Views: 72

Re: #25 on Molarity and Dilution of a Solution Post Assessment

I did this post assessment module a few days ago but if I remember correctly I got it right using these steps: Convert the 5.00 g KMnO4 to mols using its molar mass (158.04g/mol) and you'll get 0.0316 mol. Then using the volume you're given, find the molarity of the solution. Make sure to change the...
Tue Oct 06, 2020 8:26 pm
Forum: Significant Figures
Topic: 5000 vs 5000.0
Replies: 7
Views: 89

Re: 5000 vs 5000.0

I like that trick Brittney! That'll be really helpful when determining which zeros are significant. Thanks! :)