Search found 68 matches

Tue Jan 12, 2021 9:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: fully dissociated ionic compounds
Replies: 3
Views: 20

Re: fully dissociated ionic compounds

Hi! Is this in relation specifically to acids and bases? If so, the acid or base will fully dissociate into its ions if it is a strong acid or base. Strong acids include HCl, HBr, HI, H₂SO₄, HNO₃, HClO₄, and HClO₃. Strong bases include Group 1 and Group 2 oxides and hydroxides. If you're just talkin...
Tue Jan 12, 2021 5:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Question 6A.19 Part C Error? [ENDORSED]
Replies: 2
Views: 31

Re: Textbook Question 6A.19 Part C Error?[ENDORSED]

Hi!

I did the problem and I also got [OH-] = 3.2 e-15 M. I think it might be an error in the solutions, as 3.1M of H3O+ is too large to yield [OH-] values that are greater than 1e-14...

Can someone clarify whether or not Dr. Lavelle discussed this during his office hours?
Tue Jan 12, 2021 11:14 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Homework Q #4
Replies: 2
Views: 32

Re: Sapling Homework Q #4

Hi! To get the right answer the first time, I think you'd have to go with the reaction that the problem gives you. I.e., in this case, you'd assume that PCl5 is the product. Although, what you did technically isn't incorrect, I don't think. By solving with PCl5 as the reactant, you essentially flipp...
Tue Jan 12, 2021 11:11 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pKa Trend
Replies: 3
Views: 20

Re: pKa Trend

Hi! If I remember correctly from 14A, a more acidic solution will have a lower pH, a lower pKa, and a higher Ka. This is because Ka, the equilibrium constant for an acid, is [A-][H3O+]/[AH], with [A-] being the conjugate base and [AH] being the acid. The strength of an acid depends on how much it di...
Tue Jan 12, 2021 11:02 am
Forum: Student Social/Study Group
Replies: 19
Views: 49

Hi! My two must-do study techniques are doing all of the practice problems that Dr. Lavelle assigned and going to UA Workshops. Like, I cannot emphasize how good the UA Workshops are. They give you difficult problems similar to ones that have shown up on past exams so you're practically ready for an...
Mon Jan 11, 2021 7:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw= 1.0 x 10^-14
Replies: 11
Views: 59

Re: Kw= 1.0 x 10^-14

Hi! This probably isn't too helpful, but I looked around on the internet a lot and it just seems like Kw being equal to 10^-14 is universally accepted. It just... is that. For example, Khan Academy (https://www.khanacademy.org/science/ap-chemistry/acids-and-bases-ap/acids-bases-and-ph-ap/a/water-aut...
Tue Jan 05, 2021 6:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Boxes
Replies: 13
Views: 74

Re: ICE Boxes

Hi! Generally, changes in reactants are negative because we're using up the reactant to make a product. Therefore, changes in products are positive because we are making product by using up the reactant. I'm not really sure of any circumstances in which this rule would change, but please let me kno...
Tue Jan 05, 2021 6:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium 1A Question 18
Replies: 3
Views: 26

Re: Chemical Equilibrium 1A Question 18

Hi! It should be B, the ratio of the equilibrium concentrations of products to the equilibrium concentrations of reactants. K measures the amount of products over the amount of reactants at equilibrium. B is the only answer that (1) specifies that the values are at equilibrium and (2) provides the c...
Tue Jan 05, 2021 1:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Boxes
Replies: 13
Views: 74

Re: ICE Boxes

Hi! Generally, changes in reactants are negative because we're using up the reactant to make a product. Therefore, changes in products are positive because we are making product by using up the reactant. I'm not really sure of any circumstances in which this rule would change, but please let me know...
Mon Jan 04, 2021 10:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #5
Replies: 5
Views: 45

Re: Sapling #5

Hi! I don't think Dr. Lavelle has gone over this in lecture yet (and unfortunately I haven't done this problem yet either), but I'll give it my best shot based on what I remember from AP Chem and from last quarter. The reaction at the top is a big reaction comprised of multiple little reactions, whi...
Mon Jan 04, 2021 8:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Homework Week 1-Problem#2
Replies: 5
Views: 52

Re: Sapling Homework Week 1-Problem#2

Hi! Just to get you started, you can find molar concentration by dividing number of moles by liters. So the initial concentration of SO3 would be .920mol/5L and the final concentration of O2 would be .150mol/5L. I haven't actually done this problem yet, so the best advice I can give you as a walkthr...
Mon Jan 04, 2021 1:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: post-module #20
Replies: 6
Views: 52

Re: post-module #20

Hi! I think where you might have went wrong is in the numerator. In the K expression, you have [SO3]^2/[O2][SO2]^2. You're right in that [SO3] must equal +2x, but when you squared 2x, you ended up with 2x^2 instead of 4x^2 (the exponent distributes to both the coefficient and the variable). Using 4x...
Mon Dec 07, 2020 3:28 pm
Forum: Bronsted Acids & Bases
Topic: Identifying Bronsted Acid and Base
Replies: 2
Views: 15

Re: Identifying Bronsted Acid and Base

For problems like that, I like to consider the compound's potential to form a coordinate covalent bond with a proton (in which case the compound would be a base) or the compound's potential to lose a proton (making the compound an acid) based on formal charge. For example, NH3 has a lone pair. That ...
Mon Dec 07, 2020 3:18 pm
Forum: Bronsted Acids & Bases
Topic: O2- in water makes 2 OH-?
Replies: 3
Views: 40

Re: O2- in water makes 2 OH-?

From what I understand O2- in water makes 2OH- because one of the H from the water forms a coordinate covalent bond with the O2-. Thus, the O2- gains an H+ to become OH-, and the H2O loses an H+ to become OH-.

I'm not entirely sure though, so please correct me if I'm wrong!
Mon Dec 07, 2020 12:40 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Definition of Ka and pKa
Replies: 2
Views: 9

Re: Definition of Ka and pKa

Ka refers to the equilibrium constant for a reaction involving an acid in an aqueous reaction, with the equation being Ka = [A-][H+]/[AH], (AH is the acid before it donated a proton and A- is the conjugate base). pKa puts this Ka value into nicer numbers by taking the -log of Ka (we can say pKa = 4 ...
Mon Dec 07, 2020 11:49 am
Forum: Administrative Questions and Class Announcements
Topic: Potential Problem with Lecture #28 Upload
Replies: 1
Views: 43

Re: Potential Problem with Lecture #28 Upload

Yeah, I had that same problem. I had to switch to a different browser (Google Chrome to Safari) to play the video.
Mon Dec 07, 2020 11:46 am
Forum: Calculating the pH of Salt Solutions
Topic: explanation of 10^-14
Replies: 3
Views: 16

Re: explanation of 10^-14

In terms of the balancing part, I think he means that [H3O+] x [OH-] will always equal 10^-14 M. Thus, if you know [H3O+], you pretty much know [OH-].

Hope this helps!
Fri Dec 04, 2020 11:53 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pKa VS pH
Replies: 2
Views: 18

Re: pKa VS pH

pKa and pH do run on the same scales and have the same sort of proportionality to the strength of an acid (lower pH or pKa = more acidic, as you stated), but they measure different things. Ka refers to the equilibrium constant for a reaction involving an acid in an aqueous reaction. Since Ka = [A-][...
Fri Dec 04, 2020 11:46 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating ligands and polydentate compounds
Replies: 3
Views: 21

Re: Chelating ligands and polydentate compounds

Based on all the examples we've done and something a TA said, I would say that a polydentate ligand will always form a chelate. The definition of a polydentate ligand is a ligand that is attached to a central transition metal atom with 2 or more bonds. Those multiple bonds have no choice but to clos...
Tue Dec 01, 2020 4:16 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Dentates
Replies: 3
Views: 54

Re: Dentates

Hi! While dentates do help us determine the coordination number of a compound, classifying a ligand as mono or polydentate helps us understand the overall structure of the coordination complex as well. To be honest, I think that the best way to determine is a dentate is mono, bi, tri, etc. is to dra...
Tue Dec 01, 2020 2:44 pm
Forum: Coordinate Covalent Bonds
Topic: mono, bi, tridentate
Replies: 2
Views: 37

Re: mono, bi, tridentate

To add onto what Sophia said, kind of. If a ligand has multiple lone pairs, it could donate these pairs to a TM as long as the ligand has single bonds that allow the atoms to orient their lone pairs towards the ligand, or as long as the ligand's lone pairs are naturally close enough together to crea...
Mon Nov 30, 2020 9:17 pm
Forum: Biological Examples
Topic: Hemoglobin Subunits
Replies: 3
Views: 48

Re: Hemoglobin Subunits

Hi!

I believe that myoglobin refers to the Fe + heme complex + amino acid histidine. Thus, I think that hemoglobin has 4 of these Fe + heme + amino acid structures.

Although, I might be wrong because I'm not exactly sure what protein you're talking about. Could you clarify?
Tue Nov 24, 2020 10:31 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 9
Views: 43

Re: Resonance

Hi! The best way to visualize resonance is probably through Lewis structures. Take NO_3-, for example. The one double bond between the N and the O can occur between the N and any O. When a double or triple bond can occur indiscriminately between multiple sets of the same 2 atoms in a molecule, the m...
Tue Nov 24, 2020 10:26 pm
Forum: Octet Exceptions
Topic: Octet Exceptions
Replies: 10
Views: 71

Re: Octet Exceptions

Hi! Elements in the p block that have an empty d orbital to fill can have an expanded octet. For example, xenon has the electron configuration. [Kr] 4d^10 5s^2 5p^6. Note that the 5d orbital isn't filled for xenon, so xenon has the potential to have more than 8 electrons in its outer shell, like it ...
Tue Nov 24, 2020 8:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #6
Replies: 5
Views: 57

Re: Sapling #6

With this in mind, we remove the electron clouds because the question asks for the molecular geometry. Hey Courtney! Your answer was really helpful :-) I was just wondering how we know the question is asking for molecular geometry. I recall Dr. Lavelle saying something in his lectures about naming ...
Mon Nov 23, 2020 7:22 pm
Forum: Student Social/Study Group
Topic: Exercising Our Minds and Bodies
Replies: 92
Views: 462

Re: Exercising Our Minds and Bodies

Lavelle has mentioned the importance of exercising our mind and body so I was interested to see what types of exercises everyone was up to! I usually just go for walks/runs with my dog. There are some really good exercise videos on youtube too! I usually do a full body one from Madfit or Pamela Rei...
Mon Nov 23, 2020 7:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Nonpolar molecules
Replies: 3
Views: 30

Re: Nonpolar molecules

Hi! Molecules are nonpolar when the electrons between each atom are shared equally in a nonpolar covalent bond, or when the dipole moments cancel out. For example, H_2 is nonpolar because each H atom pulls on the shared electrons equally. CCl_4 is also nonpolar because while Cl is more electronegati...
Mon Nov 23, 2020 7:07 pm
Forum: Hybridization
Replies: 3
Views: 43

Hi! If you recall, there is only one type of s orbital and there are three types of p orbitals. sp^3 hybridization has 4 hybrid orbitals because you're combining the one s orbital and all three p orbitals into one energy level, yielding a total of four orbitals in one energy level. sp^2 hybridizatio...
Mon Nov 16, 2020 12:39 pm
Forum: General Science Questions
Topic: midterm 2
Replies: 4
Views: 53

Re: midterm 2

As far as I know, we just need to be able to qualitatively discuss dipole moments.
Mon Nov 16, 2020 12:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion of a Bonding-Bonding Pair
Replies: 6
Views: 47

Re: Repulsion of a Bonding-Bonding Pair

Hello!

He means that a lone pair of electrons and another lone pair repel each other more than a lone pair and a bonding pair do. Likewise, a lone pair and a bonding pair repel each other more than a bonding pair and another bonding pair do.

I hope this helps!
Mon Nov 16, 2020 11:52 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Unpaired Electrons
Replies: 2
Views: 24

Re: Unpaired Electrons

To be honest, I think it's more valuable to draw out the orbitals in the outer shell (that line and arrow diagram) to get to an absolutely foolproof answer rather than trying to get to the answer faster. You might miss some exceptions (like Cr and Cu) otherwise. You can cut down on the time you spen...
Mon Nov 16, 2020 11:48 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: intermolecular energy equation clarification
Replies: 4
Views: 39

Re: intermolecular energy equation clarification

We essentially just need to know the qualitative relationships between the interaction potential energy (Ep) and the polarizability (alpha) of the molecules/atoms, as well as that between Ep and the distance (r) in between the two atoms/molecules. r has a much more significant impact on the Ep in th...
Mon Nov 16, 2020 8:28 am
Forum: Lewis Structures
Topic: Lewis Structure w/ 4+ atoms
Replies: 4
Views: 58

Re: Lewis Structure w/ 4+ atoms

I'd probably use formal charge for this one. If there's no other way to bring the formal charges of each atom to 0, you've likely got the correct structure. But I agree in that some structures are just really funky and kind of hard to get to; I struggled a lot with that as well.
Tue Nov 10, 2020 6:51 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s before 3d?
Replies: 6
Views: 74

Re: 4s before 3d?

Before the 3d orbital is filled, the 4s orbital is lower in energy. However, once the 3d orbital gets filled, it becomes lower in energy than the 4s orbital. An atom loses electrons from the 4s orbital before the 3d orbital because n=4 is farther away from the nucleus than n=3, so the nucleus can ho...
Tue Nov 10, 2020 6:49 pm
Forum: Dipole Moments
Topic: Negative Energy
Replies: 4
Views: 55

Re: Negative Energy

Yeah, you pretty much got it. Energy is positive when trying to break a bond because energy needs to go into that system to break the bond. Creating a bond under favorable circumstances releases energy, as the atoms involved become more stable at a lower energy. Thus, energy is negative when a bond ...
Tue Nov 10, 2020 3:28 pm
Forum: Dipole Moments
Topic: Dipole-Induced Dipole
Replies: 4
Views: 58

Re: Dipole-Induced Dipole

Ohh ok, I was confused - my explanation was on the Cl-Cl interaction. So if there is a Cl2 molecule interacting with another Cl2 molecule, you would have a dipole-induced dipole even though both molecules each have a net 0 charge (for the same reason as the first explanation, because the electrons ...
Tue Nov 10, 2020 12:24 pm
Forum: Dipole Moments
Topic: Dipole-Induced Dipole
Replies: 4
Views: 58

Re: Dipole-Induced Dipole

To me, van der waals interactions make sense because the electrons around atoms aren't stagnant. So these temporary charges arise from electrons moving around (more of the cloud being at one end of the molecule would result in an instantaneous dipole because one side has more negative charge). So C...
Tue Nov 10, 2020 12:21 pm
Forum: Ionic & Covalent Bonds
Topic: Increasing Covalent Character
Replies: 3
Views: 48

Re: Increasing Covalent Character

I'm not entirely sure, but I think solubility refers to how easily a compound can dissociate into ions when put in a solution. Since there is increasing covalent character and decreasing ionic character, the compound is less likely to break up into discrete ions. As a general rule of thumb, ionic co...
Tue Nov 03, 2020 6:55 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Formation of Ions
Replies: 5
Views: 49

Re: Formation of Ions

I know that we remove electrons from the 4s orbital first because it's in a completely different shell than the 3d orbital, and this n=4 shell is farther away so the nucleus holds the electrons in this shell. I think that we fill up the 4s orbital first because before the 3d orbital has any electron...
Tue Nov 03, 2020 5:50 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and Resonance Structures
Replies: 4
Views: 44

Re: Formal Charge and Resonance Structures

It's better to have a -1 formal charge on a single O atom! You want to get as many atoms to have a formal charge of 0 as possible because it takes a lot of energy to separate formal charges.
Tue Nov 03, 2020 10:48 am
Forum: Ionic & Covalent Bonds
Topic: NH4+
Replies: 5
Views: 54

Re: NH4+

NH4+ is a cation, so you can think of N as having one less electron than it normally has. Thus, N now has the capacity to create 4 bonds. At least, that's how I think of it. I don't know if that's how it works chemically, but doing the math for Lewis structures: N has 5 valence electrons. H has 1 va...
Mon Nov 02, 2020 5:54 pm
Forum: Ionic & Covalent Bonds
Topic: 2A #9
Replies: 2
Views: 39

Re: 2A #9

Hi! Note that the electron configuration leaves out the 5s^2 state because those electrons would technically be in the outermost shell. Thus, the configuration that the textbook gives you is already ionized with a 2+ charge. From that point, you would just need to count the elements in the 3d state ...
Mon Nov 02, 2020 5:47 pm
Forum: Quantum Numbers and The H-Atom
Topic: quantum number-s- vs p- orbitals
Replies: 3
Views: 44

Re: quantum number-s- vs p- orbitals

Hi! I thought it would be valuable to add on the fact that the energies of the subshells are s<p<d<f because the s-orbital has an electron density that is closer to nucleus than the p-orbital, and the p-orbital has an electron density that is closer to the nucleus than the d-orbital, and so forth. I...
Tue Oct 27, 2020 7:14 pm
Forum: DeBroglie Equation
Topic: When to use De Broglie equation? [ENDORSED]
Replies: 7
Views: 110

Re: When to use De Broglie equation?[ENDORSED]

Ayesha Aslam-Mir 2E wrote:On the formula sheet, we have the De Broglie equation, and another one that is E=momentum times c. In which case would we use one or the other? Or are both valid?

I've personally never used that equation. I just know that it's used in the derivation of the De Broglie equation!
Tue Oct 27, 2020 3:54 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Textbook Problem 1B.27
Replies: 1
Views: 48

Re: Textbook Problem 1B.27

Hi Megan!

Your answer is correct. The textbook makes the error of using 5 for delta v instead of 10. Dr. Lavelle addresses this in his Solution Manual Errors file on his website :-)
Mon Oct 26, 2020 9:54 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2px
Replies: 2
Views: 33

Re: 2px

Hi! n represents the shells, so the big 2 comes from that. When l=1, it always refers to the p subshell. Having m=+1 being on the x-axis is kind of just convention. You could say that m=+1 indicates the y- or z-axis is you wanted to; it really doesn't matter. The problem will usually specify what ax...
Mon Oct 26, 2020 9:49 am
Forum: DeBroglie Equation
Topic: When to use De Broglie equation? [ENDORSED]
Replies: 7
Views: 110

Re: When to use De Broglie equation?[ENDORSED]

To my understanding, you use the de Broglie equation when the particle has rest mass (i.e., electrons, neutrons, atoms, etc.). Equations like c = lambda x frequency and E = h x frequency (note that V = frequency in these equations, not velocity) are used for things like photons, which have no rest m...
Mon Oct 26, 2020 9:45 am
Forum: Properties of Electrons
Topic: Electron Transition series for the Hydrogen Atom
Replies: 1
Views: 34

Re: Electron Transition series for the Hydrogen Atom

Hi Megan! As far as I know, for we will only need to know the Balmer and Lyman series for the midterm. However, if you know which ones the Lyman and Balmer series are, you can just assume that the Paschen series is the not n_1 or n_2, and therefore should be n_3. These transitions can begin from any...
Wed Oct 21, 2020 9:52 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Final vs Initial State
Replies: 4
Views: 40

Re: Final vs Initial State

Personally, I like to label my variables as n_final and n_initial or n_f and n_i for short. However, I know that Dr. Lavelle likes to label them as n_2 and n_1 instead of n_f and n_i, respectively. It's really up to you regarding how you would want to differentiate between the two "n's."
Mon Oct 19, 2020 4:57 pm
Forum: DeBroglie Equation
Topic: Measurable Wavelike Properties
Replies: 4
Views: 35

Re: Measurable Wavelike Properties

I believe Dr. Lavelle said that things with wavelengths greater than 1x10^-15 have detectable wavelike properties. However, conceptually speaking, every moving object with momentum has wavelike properties; it's just a matter of being able to see this properties.
Mon Oct 19, 2020 10:38 am
Forum: Photoelectric Effect
Topic: Units of the Work Function
Replies: 7
Views: 49

Re: Units of the Work Function

At the proper frequency, one photon will eject one electron, so we give answers in terms of energy per electron. The question will often specify if it wants the answer in energy per mole of electron.
Mon Oct 19, 2020 10:31 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: 1A.15 Empirical Equation
Replies: 7
Views: 57

Re: 1A.15 Empirical Equation

Hello everyone! I was scrolling through this forum and I know that there are a LOT of different posts about this question. I was just wondering if anyone had tried solving it using the empirical formula, E_n = -hR/n^2, rather than Rydberg's equation, V = -R[1/n_1^2 - 1/n_2^2]. I'm trying to do it t...
Mon Oct 19, 2020 10:16 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: 1A.15 Empirical Equation
Replies: 7
Views: 57

Re: 1A.15 Empirical Equation

Hello Brittney, So yes, I did do it using the empirical formula. So because the problem told us that it was observed in the UV spectrum, we know that the lowest principal quantum energy level is n=1. Because it indicates that an emission of light was observed, that means that n=1 was the final ener...
Mon Oct 19, 2020 9:43 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: 1A.15 Empirical Equation
Replies: 7
Views: 57

1A.15 Empirical Equation

Hello everyone! I was scrolling through this forum and I know that there are a LOT of different posts about this question. I was just wondering if anyone had tried solving it using the empirical formula, E_n = -hR/n^2, rather than Rydberg's equation, V = -R[1/n_1^2 - 1/n_2^2]. I'm trying to do it th...
Thu Oct 15, 2020 5:42 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Post module 22
Replies: 1
Views: 36

Re: Post module 22

Since you found the kinetic energy per electron already, you just need to convert that value to kinetic energy per mole of electrons. There are 6.022x10^23 electrons in one mole of electrons. Hence, you would multiply your answer to the first part by Avogadro's number so that the electrons cancel ou...
Thu Oct 15, 2020 3:00 pm
Forum: Photoelectric Effect
Topic: Wavelength of Electrons
Replies: 2
Views: 40

Re: Wavelength of Electrons

I believe you'd use the De Broglie equation, wavelength = Planck's constant/momentum, where momentum = velocity x mass.
Thu Oct 15, 2020 11:56 am
Forum: Properties of Light
Topic: Does light lose energy the farther it travels?
Replies: 8
Views: 93

Re: Does light lose energy the farther it travels?

Hmm, that's an interesting point! I haven't finished the modules yet, so maybe I'm missing something, but E=hV doesn't account for distance at all. Maybe the light interacts with particles in the air on its journey to various surfaces. Also, regarding your point about the outer planets being colder,...
Tue Oct 13, 2020 8:18 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post-Module Question 42
Replies: 2
Views: 34

Re: Atomic Spectra Post-Module Question 42

Hi! So first off with this information you know you must be using the energy level equation of frequency = -R(1/(initial^2) - 1/(final^2)) From there you plug in the frequency and the energy level 4 in the final n level and solve for the initial energy level. You should get a number very close to a...
Tue Oct 13, 2020 8:14 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post-Module Question 41
Replies: 3
Views: 19

Re: Atomic Spectra Post-Module Question 41

Thanks to you both! That really helped :-)
Tue Oct 13, 2020 11:53 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post-Module Question 41
Replies: 3
Views: 19

Atomic Spectra Post-Module Question 41

Hello! I got this question right via process of elimination, but I don't really understand why it's right. 41. For the hydrogen atom which statement is true? A. The transition from n = 5 to n = 3 involves greater energy than one from n = 4 to n = 2. B. The transition from n = 4 to n = 2 emits radiat...
Tue Oct 13, 2020 11:49 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post-Module Question 42
Replies: 2
Views: 34

Atomic Spectra Post-Module Question 42

Hi all! Could someone please guide me through this question? I have a general idea of where to go, but none of my answers match the options so my thinking is probably flawed somewhere. Thanks! 42. An excited hydrogen atom emits light with a frequency of 1.14 x 1014 Hz to reach the energy level n = 4...
Wed Oct 07, 2020 9:35 am
Forum: Empirical & Molecular Formulas
Topic: Fundamentals L. 39
Replies: 7
Views: 100

Re: Fundamentals L. 39

What I'm further wondering is how does one know that it's tin (IV) oxide as opposed to any other variant of tin?

Responding to my own post because I realized that tin (IV) is the only variant of tin that has a 2:1 charge ratio when coupled with oxygen.
Tue Oct 06, 2020 8:23 pm
Forum: Significant Figures
Topic: 5000 vs 5000.0
Replies: 7
Views: 89

Re: 5000 vs 5000.0

Just to add on with a fun mnemonic that my AP Chem teacher taught me: For sig figs, remember the A tlantic- P acific rule. If there is a decimal P resent, start from the P acific Ocean side (left) and disregard any zeros that begin from that direction as significant figures. If there is a decimal A ...
Tue Oct 06, 2020 5:21 pm
Forum: Empirical & Molecular Formulas
Topic: Fundamentals L. 39
Replies: 7
Views: 100

Re: Fundamentals L. 39

I made the mistake of assuming the oxygen in the air was the molecule O2 so my empirical formula was SnO. This was because the molar mass of my oxygen molecule was double (15.999 * 2 atoms). Huh. I made the same mistake and still got SnO_2 as my answer, as I ended up with a 1:1 ratio of Sn and O_2 ...
Tue Oct 06, 2020 12:26 pm
Forum: SI Units, Unit Conversions
Topic: Formula Units
Replies: 8
Views: 68

Re: Formula Units

I had the same question. A formula unit is one unit of a full compound. They're similar to how a molecule is one unit of a molecular compound, but the term "formula units" is specifically used to refer to ionic compounds.
Mon Oct 05, 2020 6:15 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E9
Replies: 7
Views: 110

Re: E9

The term "formula units" is used when referring to an ionic compound in comparison to a molecular compound. Sorry, I still don't quite understand how that indicates that you should find the number of molecules. Could you elaborate? A formula unit is essentially one unit of a full compound...
Mon Oct 05, 2020 5:58 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E9
Replies: 7
Views: 110

Re: E9

Frankie Mele 2E wrote:The term "formula units" is used when referring to an ionic compound in comparison to a molecular compound.

Sorry, I still don't quite understand how that indicates that you should find the number of molecules. Could you elaborate?
Mon Oct 05, 2020 5:11 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E9
Replies: 7
Views: 110

Re: E9

The formula units refers to the total number of molecules of Epsom salt, which is different from the total number of Oxygen atoms. How did you know that the formula units refer to the total number of molecules of Epsom salt? Does the term "formula units" always refer to the total number o...