Search found 35 matches

by Jessica Li 1F
Tue Nov 12, 2019 9:09 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 3F19.c.
Replies: 2
Views: 10

3F19.c.

Why does the different structure of the 2 molecules, pentane and 2,2-dimethylpropane, make their boiling points different?
by Jessica Li 1F
Thu Nov 07, 2019 11:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Resonance Delocalization
Replies: 5
Views: 26

Re: Resonance Delocalization

In resonance structures, electrons are not just limited to the single/double bonds as seen in the different Lewis structures, but actually delocalized, or spread out, among all of these bonds. Therefore, no resonance structure is the actual Lewis structure of the molecule. Rather, the molecule is a ...
by Jessica Li 1F
Thu Nov 07, 2019 11:00 pm
Forum: Octet Exceptions
Topic: radicals
Replies: 3
Views: 18

Re: radicals

To second that, the more electronegative atom usually wants more electrons. If it is that the radical electron would give that element more electrons, that it would get the electron on the Lewis structure and vice versa. However, formal charge is also important, so I'd keep that in mind.
by Jessica Li 1F
Wed Nov 06, 2019 10:40 am
Forum: Administrative Questions and Class Announcements
Topic: KAREN SUN 5-7PM WORKSHOP - DOWNLAOD WORKSHEETS HERE
Replies: 44
Views: 1199

Re: KAREN SUN 5-7PM WORKSHOP - DOWNLAOD WORKSHEETS HERE

For #10 on worksheet 3, why is wavelength not related to speed per De Broglie's equation?

Here is the question: 10. Which of the following statements regarding electromagnetic radiation is true?
by Jessica Li 1F
Tue Nov 05, 2019 10:44 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Constant
Replies: 1
Views: 18

Rydberg Constant

For the Rydberg equation, does the negative sign cancel out?
by Jessica Li 1F
Tue Nov 05, 2019 10:42 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Dino nuggets 11b
Replies: 3
Views: 38

Re: Dino nuggets 11b

Emission means releasing energy, which means that delta E itself will be negative, as energy is lost.
The energy of a photon, however, can never be negative, so it is always the positive absolute value of delta E.
by Jessica Li 1F
Wed Oct 30, 2019 6:37 pm
Forum: Formal Charge and Oxidation Numbers
Topic: When would a compound not have FC=0?
Replies: 2
Views: 22

Re: When would a compound not have FC=0?

It would be when the compound itself is charged/a polyatomic ion.To add on to the previous answer, since SO32- has a 2- charge overall already, the formal charges (if correctly calculated) should also come out to -2.
by Jessica Li 1F
Wed Oct 30, 2019 6:34 pm
Forum: Octet Exceptions
Topic: expanded valence shells
Replies: 2
Views: 19

Re: expanded valence shells

I think stability depends a lot on the formal charges of the atoms involved. Since atoms with expanded valence shells tend to have lesser formal charges (hence why they are expanded rather than not), I would say that they are definitely stable.
by Jessica Li 1F
Wed Oct 30, 2019 6:33 pm
Forum: Lewis Structures
Topic: Valence Electrons from Periodic Table
Replies: 10
Views: 58

Re: Valence Electrons from Periodic Table

I think it's helpful if you have time to write down the electron configuration. Then, you can just count all the subscripts in the highest n level and add them up. This helps prevent confusion with the d orbitals. For instance, for Zinc, the config would be 1s2 2s2 2p6 3s2 3p6 3d10 4s2. Since n =4 i...
by Jessica Li 1F
Wed Oct 30, 2019 6:30 pm
Forum: Ionic & Covalent Bonds
Topic: Partial charge
Replies: 4
Views: 20

Re: Partial charge

I believe that covalent bonds have partial charges because they only have semi-ionic characteristics, while ionic bonds have actual full charges (i.e. Na+ and Cl- (the plus and minus charges)) and their own semi-covalent characteristics.
Correct me if I'm wrong though!
by Jessica Li 1F
Wed Oct 30, 2019 11:45 am
Forum: Lewis Structures
Topic: Valence electrons
Replies: 5
Views: 40

Re: Valence electrons

However, since phosphorus has a technically empty 3d orbital, it can bond to other elements in a way so that it can have up to 10 valence electrons, as with PCl5.
Hope that clarifies things!
by Jessica Li 1F
Fri Oct 25, 2019 4:14 pm
Forum: Lewis Structures
Topic: Single or Double Bonds
Replies: 4
Views: 22

Re: Single or Double Bonds

For elements who cannot have expanded octets, you want to draw bonds in a way so all elements (except H and He) have octets. For instance, CO2 would need double bonds, while CF4 only needs single bonds. For elements who can have expanded octets, you want to calculate the formal charges of all the at...
by Jessica Li 1F
Fri Oct 25, 2019 4:12 pm
Forum: Ionic & Covalent Bonds
Topic: Midterm 2
Replies: 4
Views: 32

Re: Midterm 2

I think there's only one midterm (on Nov. 6), and that one will be cumulative all the way from Test 1.
by Jessica Li 1F
Fri Oct 25, 2019 4:12 pm
Forum: Octet Exceptions
Topic: Expanded Valence Shells
Replies: 4
Views: 16

Re: Expanded Valence Shells

P, S, and Cl are definitely not the only elements that can have expanded octets. They are just when the expanded octet for elements begins - elements with associated d orbitals should all be able to have expanded octets.
by Jessica Li 1F
Wed Oct 23, 2019 11:38 am
Forum: Lewis Structures
Topic: Lewis Structure angles
Replies: 3
Views: 20

Lewis Structure angles

When drawing Lewis structures, does the angle at which we draw them have to be accurate? For example, with NO3-, making the oxygens perpendicular to N versus at a slanted angle?
by Jessica Li 1F
Mon Oct 21, 2019 5:46 pm
Forum: Photoelectric Effect
Topic: Module Assessment Question
Replies: 2
Views: 28

Module Assessment Question

The question is "Photoelectric experiments gave rise to a new equation relating the energy of light to its frequency. Select the right equation."

Is the answer E = hv instead of the one with work function and kinetic energy, and why?
by Jessica Li 1F
Fri Oct 18, 2019 3:39 pm
Forum: DeBroglie Equation
Topic: Rydberg and De Brogile
Replies: 3
Views: 32

Re: Rydberg and De Brogile

I think it depends on what values you are given and what the question is asking for. The Rydberg equation is usually used when you're trying to find which energy levels an electron is jumping to/from, or when you're trying to find the wavelength of emission when given the energy levels the electron ...
by Jessica Li 1F
Fri Oct 18, 2019 3:35 pm
Forum: *Particle in a Box
Topic: 1B. Quantum Theory and model of an atom
Replies: 2
Views: 50

Re: 1B. Quantum Theory and model of an atom

You could also draw in possible paths the electron could take/be to show that you are uncertain of where exactly the electron is.
by Jessica Li 1F
Fri Oct 18, 2019 3:34 pm
Forum: Properties of Electrons
Topic: Equations for Test
Replies: 9
Views: 53

Equations for Test

What equations relevant to the quantum unit will be given on a test? Will we have to memorize the Schroedinger Equation, etc.?
by Jessica Li 1F
Fri Oct 18, 2019 3:31 pm
Forum: *Shrodinger Equation
Topic: Quantum Number
Replies: 2
Views: 40

Re: Quantum Number

If an atom has an electron configuration such that some electrons are paired in an orbital, and you are trying to find an electron in a paired orbital, the fourth quantum number would help distinguish between the one with an up spin and the one with a down spin. Therefore, yes, the fourth quantum nu...
by Jessica Li 1F
Fri Oct 18, 2019 3:24 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: d orbitals
Replies: 1
Views: 23

d orbitals

I know that the p orbitals can be written as px, py, and pz, but what about the d orbitals?
Also, for tests, will we have to be specific and write out the subscripts, or can we just write, for example in carbon, 1s22s22p2 instead of 1s2 2s2 2px?
by Jessica Li 1F
Fri Oct 18, 2019 3:13 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s and 3d electron configurations
Replies: 1
Views: 26

4s and 3d electron configurations

In lecture today, Professor Lavelle talked about how when writing electron configurations, we should do, for example with Scandium, [insert noble gas]3d^1 4s^2 and NOT [noble gas]4s^2 3d^1. However, in my high school chemistry class, we always flipped 4s and 3d - I'm wondering why this is? I also un...
by Jessica Li 1F
Mon Oct 14, 2019 4:41 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty Equation
Replies: 4
Views: 23

Re: Uncertainty Equation

Just using the equation, (uncertainty in momentum)(uncertainty in position) >= h/4pi, you can tell that if one of the factors increases and you want the product to stay the same, the other factor must decrease.
Hope this helps!
by Jessica Li 1F
Mon Oct 14, 2019 4:39 pm
Forum: DeBroglie Equation
Topic: HW Question 1B.23
Replies: 2
Views: 26

Re: HW Question 1B.23

To add on, all such values should be given on the reference sheet, especially for tests, including the mass of an electron as well.
by Jessica Li 1F
Mon Oct 14, 2019 4:36 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post-Module Question
Replies: 3
Views: 30

Re: Atomic Spectra Post-Module Question

I agree with the above answers. Although you get a negative value for frequency when you calculate using the equation, it is because frequency is emitted and therefore "lost." When anything is "lost," it will be expressed as a negative value in an equation. However, the actual fr...
by Jessica Li 1F
Mon Oct 14, 2019 4:31 pm
Forum: Properties of Light
Topic: 1A.15
Replies: 4
Views: 67

Re: 1A.15

Yeah, you have to assume that the final energy level is n = 1. Then you can find the energy emitted using the c = wavelength(frequency) equation and the E = hv equation to input into the Rydberg equation.
by Jessica Li 1F
Fri Oct 04, 2019 11:41 pm
Forum: Balancing Chemical Reactions
Topic: Reaction Stoichiometry L.35
Replies: 2
Views: 32

Re: Reaction Stoichiometry L.35

First, you should balance the equations to the following (states of matter not included): Fe + Br2 -> FeBr2 3FeBr2 + Br2 -> Fe3Br8 Fe3Br8 + 4Na2CO3 -> 8NaBr + 4CO2 + Fe3O4 Then use dimensional analysis and mole ratios to solve, from the amount of NaBr given to iron: 2.50 t NaBr * (1000 kg NaBr/1 t N...
by Jessica Li 1F
Fri Oct 04, 2019 11:27 pm
Forum: Balancing Chemical Reactions
Topic: Chemical Equations H11
Replies: 1
Views: 31

Re: Chemical Equations H11

It would be:
Fe2O3(s)+3CO(g)-->2Fe(s)+3CO2(g)
by Jessica Li 1F
Fri Oct 04, 2019 11:26 pm
Forum: Molarity, Solutions, Dilutions
Topic: Question
Replies: 3
Views: 37

Re: Question

You are supposed to multiply by 1000 to convert the liters in the Molarity measurement (which is moles/liters) into mL, and there are 1000 mL in one liter.
by Jessica Li 1F
Fri Oct 04, 2019 8:13 pm
Forum: Balancing Chemical Reactions
Topic: M9
Replies: 2
Views: 31

Re: M9

It's basically the same as any other equation, except for the compounds that are ionic and soluble in water add the (aq) subscript on the bottom. For the solids, indicate that they are solid and write them as whole compounds. However, there are also complete ionic equations in which you have to sepa...
by Jessica Li 1F
Fri Oct 04, 2019 8:10 pm
Forum: Limiting Reactant Calculations
Topic: Percent or theoretical yield
Replies: 14
Views: 93

Re: Percent or theoretical yield

I think we might, but the simple answer is just that in real life, things never go exactly right. There is a lot of potential for experimental error, as well as secondary reactions that make the actual yield lesser than the theoretical yield.
by Jessica Li 1F
Fri Oct 04, 2019 8:08 pm
Forum: Empirical & Molecular Formulas
Topic: L. 39
Replies: 2
Views: 35

Re: L. 39

To elaborate on the previous answer, for part a you want to make sure to subtract the crucible weight from the total weight to find the weight of the product itself, and then take the given mass of tin to find the percentages of both tin and oxygen, as they are the only two elements involved in the ...
by Jessica Li 1F
Fri Oct 04, 2019 8:03 pm
Forum: SI Units, Unit Conversions
Topic: SI Units
Replies: 3
Views: 42

Re: SI Units

The SI units themselves don't ascend and descend in orders of 3. I think the orders of 3 just make it a bit more convenient when converting SI units between each other, and so you don't have to memorize and name all the different powers of 10. The only major exception, as Professor Lavelle said, is ...
by Jessica Li 1F
Fri Oct 04, 2019 7:58 pm
Forum: Administrative Questions and Class Announcements
Topic: First Test in Discussion
Replies: 13
Views: 146

Re: First Test in Discussion

I like to scan or skim the problems that we need to do and see which ones are similar. Usually problems with consecutive numbers are more or less the same (i.e. E7 and E9), so if they are similar, I tend to only do one. I also tend to go for the problems later on in each Fundamentals chapter (i.e. M...
by Jessica Li 1F
Fri Oct 04, 2019 7:51 pm
Forum: Ideal Gases
Topic: Reading the textbook [ENDORSED]
Replies: 127
Views: 75083

Re: Reading the textbook [ENDORSED]

I used these for my AP Chemistry class in high school, but I think they have some college-level chem as well: https://chem.libretexts.org/ https://www.youtube.com/channel/UCEWpbFLzoYGPfuWUMFPSaoA https://www.youtube.com/watch?v=IFKnq9QM6_A&list=PLJfwA7_CzYE_qLSXH2hJkpffcrc76NjHJ Hope this helps!

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