Search found 35 matches

by Melanie Lin 3B
Sun Nov 22, 2020 9:10 pm
Forum: Bond Lengths & Energies
Topic: Bond Strength in DNA
Replies: 12
Views: 49

Re: Bond Strength in DNA

That's correct! With more hydrogen bonds, GC pairs are markedly stronger than AT pairs. So DNA with low GC ratio often times are less stable compared to DNA with high GC ratio!
by Melanie Lin 3B
Sun Nov 22, 2020 9:06 pm
Forum: Bond Lengths & Energies
Topic: Boiling/Melting Point
Replies: 17
Views: 58

Re: Boiling/Melting Point

Hi Natalie! You generally look into intermolecular forces to see if the molecule is nonpolar or polar. Once you figure that out, you determine the type of intramolecular force that the molecules have with each other. So the BP and MP are mostly determined by the strength of the intramolecular forces.
by Melanie Lin 3B
Sun Nov 22, 2020 9:04 pm
Forum: Bond Lengths & Energies
Topic: Textbook Question 3F.15
Replies: 7
Views: 37

Re: Textbook Question 3F.15

Since As has 5 valence electrons, it perfectly bonds to the 5 F atoms and leaves no lone pairs, making it a nonpolar molecule. With AsF3, a lone pair is left on the As atom, so the molecule becomes nonpolar. With nonpolar molecules, the IMFs are much stronger than with nonpolar ones so the boiling p...
by Melanie Lin 3B
Sun Nov 22, 2020 8:59 pm
Forum: Bond Lengths & Energies
Topic: Melting Point
Replies: 12
Views: 39

Re: Melting Point

Adding onto what Gina said, you can use the list of IMF's that Lavelle discussed in his lectures to see which molecules have stronger interactions depending the type of interaction.
by Melanie Lin 3B
Sun Nov 22, 2020 8:54 pm
Forum: Administrative Questions and Class Announcements
Topic: Extra Credit
Replies: 11
Views: 54

Re: Extra Credit

Extra credit would definitely be much appreciated! I'm sure there are many of us out there struggling with classes in quarantine, with all that Zoom fatigue :(
by Melanie Lin 3B
Sun Nov 15, 2020 10:07 pm
Forum: Resonance Structures
Topic: Maximum
Replies: 3
Views: 28

Re: Maximum

Hi Algernon! I think you'll have to find out by drawing the different possible Lewis structures and checking the formal charges. If they have similar formal charges and are only switching bonds/number of bonds, they are generally identified as resonance structures. Sadly, as of what I know so far, t...
by Melanie Lin 3B
Sun Nov 15, 2020 10:05 pm
Forum: Resonance Structures
Topic: bond character
Replies: 8
Views: 30

Re: bond character

I'm confused on the hydrogen bonding question, what are the rules that apply to h bonds? Does anyone know how to remember them? Hi Alyssa! To add onto what Gina mentioned, take into account the dipoles of those atoms. For example, in CH4, the H atoms don't have any dipole moments so they can't hydr...
by Melanie Lin 3B
Sun Nov 15, 2020 9:58 pm
Forum: Resonance Structures
Topic: bookwork 2C.15
Replies: 2
Views: 10

Re: bookwork 2C.15

Hi Hana! You can find which Lewis structure is more stable by looking at the formal charges of each atom. If the formal charges of each atom are closer to zero and add up to the overall charge of the actual molecule/polyatomic ion, then it is the most similar to the actual structure of the molecule/...
by Melanie Lin 3B
Sun Nov 15, 2020 9:54 pm
Forum: Resonance Structures
Topic: Sapling #9
Replies: 3
Views: 29

Re: Sapling #9

Hi Samaya! Regarding the oxidation thing, the problem meant to show you that you rely more on formal charge than oxidation numbers to see which structures are closer to the actual structure of the molecule.
by Melanie Lin 3B
Sun Nov 15, 2020 9:52 pm
Forum: Resonance Structures
Topic: Sapling 9
Replies: 5
Views: 26

Re: Sapling 9

The oxidation number problem was meant to show you that it doesn't really show which structure is more stable. You rely more on formal charge to get an idea of which structures are closer to its real form.
by Melanie Lin 3B
Sun Nov 08, 2020 8:11 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8204
Views: 1432864

Re: Post All Chemistry Jokes Here

What do you do with a dead chemist?
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Barium :(
by Melanie Lin 3B
Sun Nov 08, 2020 8:09 pm
Forum: Ionic & Covalent Bonds
Topic: Chemical Bonds
Replies: 12
Views: 31

Re: Chemical Bonds

As the number of bonds increase between atoms, the pull between them also becomes stronger and they're drawn closer together. This results in a shorter bond length between the two atoms.
by Melanie Lin 3B
Sun Nov 08, 2020 8:06 pm
Forum: Ionic & Covalent Bonds
Topic: Extra Valence Electrons
Replies: 10
Views: 46

Re: Extra Valence Electrons

Hello! Prof. Lavelle actually mentioned this in the lecture about them being the exception but since they're also going to the n=3 shell, they are able to take in more electrons.
by Melanie Lin 3B
Sun Nov 08, 2020 8:04 pm
Forum: Ionic & Covalent Bonds
Topic: Question about bond Length
Replies: 6
Views: 34

Re: Question about bond Length

Hi Noelle! You can't really determine the exact length of a bond given a certain bond unless you memorize it from online, but you can definitely determine its relative size through the bond type/strength. For example, if there's a double bond, the bond length will be shorter than it usually would be...
by Melanie Lin 3B
Sun Nov 08, 2020 8:00 pm
Forum: Significant Figures
Topic: How to use Scientific Notation
Replies: 9
Views: 66

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 exponent...
by Melanie Lin 3B
Sun Nov 01, 2020 9:59 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8204
Views: 1432864

Re: Post All Chemistry Jokes Here

So I told Sodium and Neon a super funny joke. Guess what they said:
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Na: That was SODIUM funny!
Ne: I slapped my NEON that one.
by Melanie Lin 3B
Sun Nov 01, 2020 9:54 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Textbook 1E #1
Replies: 4
Views: 28

Re: Textbook 1E #1

Hi Jaylin! I actually think all of them increase! Here's my explanation: (a) electron energy will increase as they jump to a higher energy level and stray further from the nucleus. (b) n also increases because the jump goes from n=1 to n=2 (c) l also increases because it goes from s orbital to p orb...
by Melanie Lin 3B
Sun Nov 01, 2020 9:50 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Sapling Question Number 20
Replies: 4
Views: 33

Re: Sapling Question Number 20

Hi Ian! This rule of having an electron in each orbital before filling them is actually the Hund's Rule! It basically states the order in which the orbitals are filled with electrons. Here's a link about Hund's Rule and how it works with orbital filling diagrams if you're curious: [https://courses.l...
by Melanie Lin 3B
Sun Nov 01, 2020 9:42 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Question 26 Sapling
Replies: 5
Views: 40

Re: Question 26 Sapling

Hi Brandon! There will be two equations that you have to utilize that can be found on Lavelle's equation sheet. You use ΔxΔp >= h/4π to find Δp with the Δx given to you (13 Å, which you should convert to meters). With the Δp solved for, you can find the uncertainty in velocity using the equation Δp ...
by Melanie Lin 3B
Sun Nov 01, 2020 9:39 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Sapling 26
Replies: 8
Views: 57

Re: Sapling 26

Hi Karina!
Like the previous replies, you likely forgot to use parenthesis to separate one value when dividing or some similar typing error on the calculator. It happens to the best of everyone so just make sure you double check your entries during exams!
by Melanie Lin 3B
Sun Oct 25, 2020 3:09 pm
Forum: Properties of Light
Topic: Units for wavelength/frequency
Replies: 18
Views: 84

Re: Units for wavelength/frequency

Hi Bethany! Wavelengths in the visible light region (which are the ones usually used in problems) are usually in nanometers but you will often have to convert it to meters if you need to use it in a formula (especially those containing Planck's constant). Frequencies will generally be in Hz (or s^(-...
by Melanie Lin 3B
Sun Oct 25, 2020 3:05 pm
Forum: Properties of Light
Topic: N2 vs N1
Replies: 6
Views: 65

Re: N2 vs N1

For problem #11 on the Sapling Homework (A violet line is observed at 434.0 nm in the spectrum of atomic hydrogen. Determine the values of n for the beginning and ending energy levels of the electron during the emission of energy that leads to this spectral line), why is it that 5 is N2 and 2 is N1...
by Melanie Lin 3B
Sun Oct 25, 2020 3:02 pm
Forum: Properties of Light
Topic: Sapling Homework week 2 problem 5
Replies: 11
Views: 92

Re: Sapling Homework week 2 problem 5

idella 1F wrote:Where do you get the 9.33x10^-6 from?

Hi Idella! The problem said that the wavelength was 9.33x10^-4 cm so you have to convert it to meters before plugging it into the E=hc/wavelength. In meters, the wavelength would be 9.33x10^-6.
by Melanie Lin 3B
Sun Oct 25, 2020 2:58 pm
Forum: Properties of Light
Topic: Sapling Week 2/3 HW Question 6
Replies: 7
Views: 115

Re: Sapling Week 2/3 HW Question 6

Hi all! I got super stuck on this problem for a while too! Turns out my biggest problem was mixing up my constants so maybe try making sure you have the correct units being cancelled out and having the correct numbers? Idk but aside from what Sophia said those two were what got me wrong answers.
by Melanie Lin 3B
Sun Oct 25, 2020 2:51 pm
Forum: Properties of Light
Topic: De Brogile Sapling HW Problem help
Replies: 7
Views: 76

Re: De Brogile Sapling HW Problem help

Can someone explain why you can't approach this problem the E = (0.5)mv^2 way? I feel like there are so many equations where things are equal to E but I'm unsure if the E is for the energy of photons or the energy of electrons. I am not a hundred percent sure but I think that the E= (0.5) mv^2 calc...
by Melanie Lin 3B
Fri Oct 16, 2020 4:05 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Listing quantum numbers
Replies: 3
Views: 134

Re: Listing quantum numbers

I'm sure you'll be fine since you'll still have the information/work you need to show there. Though I'm not entirely sure if listing it that way may affect future work (outside of class) like in research or showing others your work (as in it might throw people off(?)).
by Melanie Lin 3B
Fri Oct 16, 2020 4:01 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Numbers Question
Replies: 4
Views: 146

Re: Quantum Numbers Question

Mai V 4L wrote:Does anyone have a video they thinnk is a good reference for this topic?

Hey Mai! I was actually recommended this by my high school chemistry teacher but I think anyone should appreciate our Chemistry Jesus: [https://youtu.be/Aoi4j8es4gQ]. Feel free to check it out!
by Melanie Lin 3B
Fri Oct 16, 2020 3:57 pm
Forum: Trends in The Periodic Table
Topic: electronegative of the elements in the periodic table
Replies: 4
Views: 53

Re: electronegative of the elements in the periodic table

HI! Sophia and Vince pretty much have it all down but if you want a super simple one/two-sentence explanation: atoms go along the octet rule where they want to complete their outer shell (8 electrons) so as they get closer and closer to getting 8 electrons, the more they want/have stronger affinity ...
by Melanie Lin 3B
Fri Oct 16, 2020 3:54 pm
Forum: Einstein Equation
Topic: m vs nm
Replies: 66
Views: 350

Re: m vs nm

On the test, will we need to format our answers in meters or nanometers when solving for wavelength? It'll definitely depend on the question (whether it asks for a certain unit or not). Otherwise, I think answering in meters isn't wrong. It's just that often times the wavelengths are usually done i...
by Melanie Lin 3B
Fri Oct 16, 2020 3:49 pm
Forum: Administrative Questions and Class Announcements
Topic: Where can I buy a webcam for a reasonable price?
Replies: 60
Views: 921

Re: Where can I buy a webcam for a reasonable price?

My TA said we can just set up our phone and join zoom a second time, but it might be different for your section. The quiz ran smoothly for us and I just propped my phone up on a mug so she could see my desk. I think Lavelle said somewhere that if the TA has a way of seeing our workspace through zoo...
by Melanie Lin 3B
Fri Oct 09, 2020 3:48 pm
Forum: Molarity, Solutions, Dilutions
Topic: G.21
Replies: 4
Views: 29

Re: G.21

I would first try to find the moles of each solute first and convert to the moles of Potassium in each. For example, with K2S you'd double the number of moles of K2S since there are 2 K+ ions in a molecule of K2S. From there you can add up all the moles of potassium and divide it by 0.500 L (500. mL).
by Melanie Lin 3B
Fri Oct 09, 2020 3:44 pm
Forum: Molarity, Solutions, Dilutions
Topic: Sapling Week 1 HW_problem #9
Replies: 9
Views: 101

Re: Sapling Week 1 HW_problem #9

This problem is a bit wordy so I definitely understand why this problem would be difficult to piece together. If you've already found out the empirical formula, you just need to divide the given molar mass of the acid by the molar mass of the empirical formula you got.
by Melanie Lin 3B
Thu Oct 08, 2020 5:55 pm
Forum: SI Units, Unit Conversions
Topic: Significant Figures Using the Periodic Table
Replies: 13
Views: 83

Re: Significant Figures Using the Periodic Table

Does anyone have a link for the recommended periodic table mentioned? On Lavelle's Chem 14A site, he linked pdfs of a periodic table and constants so it might be better to base your numbers off that. Otherwise, most periodic tables vary between 3 to 4 decimal places, which I don't think will make a...
by Melanie Lin 3B
Thu Oct 08, 2020 5:51 pm
Forum: SI Units, Unit Conversions
Topic: Sapling Assignment 1 Question 6
Replies: 16
Views: 116

Re: Sapling Assignment 1 Question 6

Hi Isabel! The first thing you'll need to do is find the moles of CuNO3 by dividing the 2.92 g by the molar mass of CuNO3. With the M=N/V equation, you can put 0.260 M for M and the moles of CuNO3 for N. With two of the variables substituted with values, you can find the volume in liters. From there...
by Melanie Lin 3B
Tue Oct 06, 2020 11:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 221
Views: 116095

Re: Advice from a Medical Student [ENDORSED]

Thank you so much for the advice! Chemistry has definitely been a concern to study and prepare for the next few years (especially the retention of material for MCAT) and your experience and anecdotes have definitely eased my worries. Since this post is sort of old, I hope you're still doing well and...

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