## Search found 40 matches

Sun Nov 29, 2020 8:28 pm
Forum: Significant Figures
Topic: 40. versus 40
Replies: 23
Views: 60

### Re: 40. versus 40

Yup! Zeroes at the end of a digit (trailing zeros) are only significant if there is a decimal point present.
Fri Nov 27, 2020 11:15 pm
Forum: SI Units, Unit Conversions
Topic: How to memorize prefixes
Replies: 16
Views: 53

### Re: How to memorize prefixes

As others have said quizlet/flashcards are pretty helpful when trying to memorize the prefixes. Unit conversion problems help out a lot too. Good luck!
Fri Nov 27, 2020 11:07 pm
Forum: Biological Examples
Topic: Hemoglobin
Replies: 8
Views: 180

### Re: Hemoglobin

Just to add on, although both transport oxygen, hemoglobin can bind to more oxygen molecules at a time. I believe hemoglobin can bind to 4 oxygen molecules while myoglobin can only bind to 1 oxygen molecule at a time.
Fri Nov 27, 2020 11:03 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ring Structures
Replies: 9
Views: 24

### Re: Ring Structures

There's definitely a possibility it could show up on the final since there's been so many examples given in class and in sapling. Hopefully they'll given us a clue on the test if they do want us to draw a ring structure.
Fri Nov 27, 2020 10:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape Sheet
Replies: 7
Views: 32

### Re: Shape Sheet

Fri Nov 27, 2020 10:44 pm
Forum: Naming
Topic: Naming Complexes
Replies: 7
Views: 32

### Re: Naming Complexes

I agree! He'll most likely go over it in depth during next week's lectures. He's just finishing up the basics for now.
Sat Nov 21, 2020 9:56 pm
Forum: Lewis Structures
Topic: Central Atom Question
Replies: 20
Views: 70

### Re: Central Atom Question

Since H can only form one single bond, it's never the central atom. As a rule of thumb, the element with the lowest ionization energy is often the central atom.
Sat Nov 21, 2020 9:46 pm
Forum: Dipole Moments
Topic: higher dipole moment sapling #10
Replies: 5
Views: 25

### Re: higher dipole moment sapling #10

As said above, the two fluorines in COF2 cancel each other out somewhat. Oxygen is very electronegative as well, so overall the polarity in COF2 isn't as strong (relatively speaking). In comparison, the hydrogen in COHF is much less electronegative than the oxygen or fluorine, leading to the dipoles...
Sat Nov 21, 2020 9:31 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Best Formal Charge Equations
Replies: 24
Views: 76

### Re: Best Formal Charge Equations

I like using the FC = # of VE - # of dots - # of lines equation as well! I find it to the the fastest method once the lewis structure is drawn out.
Sat Nov 21, 2020 9:23 pm
Forum: Hybridization
Topic: Resonance Structures and Sigma & Pi Bonds
Replies: 6
Views: 25

### Re: Resonance Structures and Sigma & Pi Bonds

Yup! Resonance structures have sigma and pi bonds. I believe the pi bonds in resonance structures are specifically called delocalized pi bonds.
Sat Nov 21, 2020 9:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: double bonding
Replies: 8
Views: 57

### Re: double bonding

For VSPER, the molecular shape is dependent on the number of lone pairs and bonded pairs surrounding the central atom, more so than whether the bonds are single bonds or double bonds. I believe this is because the type of bond affects the bond length and strength but not the amount of repulsion it f...
Thu Nov 12, 2020 3:21 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Memorizing Formula
Replies: 4
Views: 30

### Re: Memorizing Formula

A trick I like to use is to look at the Lewis structure and count the number of lines and dots surrounding an atom. Since each line represents a bonding pair of electrons, we can count the number of shared electrons/2 by counting the number of lines surrounding the element. Similarly, since each dot...
Thu Nov 12, 2020 3:03 pm
Forum: Ionic & Covalent Bonds
Topic: Ions
Replies: 6
Views: 25

### Re: Ions

I don't think we're required to, but it is useful to have the most common ones memorized. Here's a list of the most common polyatomic ions!
https://ch301.cm.utexas.edu/help/ch301/polyatomics.pdf
Thu Nov 12, 2020 2:57 pm
Forum: Dipole Moments
Topic: Polar covalent bonds
Replies: 5
Views: 17

### Re: Polar covalent bonds

Dipole - dipole force happens between two polar molecules, making it an intermolecular force. Polar covalent bonds form between 2 atoms with different electronegativities , making it an intramolecular force. A molecule that is considered polar can experience dipole dipole with another polar molecule.
Tue Nov 10, 2020 8:15 pm
Forum: Lewis Structures
Topic: Resonance and Formal Charge
Replies: 3
Views: 31

### Re: Resonance and Formal Charge

If two structures have the same overall formal charge, then examine the location of the elements' individual formal charge. Theoretically, elements with higher electronegativity should have a negative formal charge since they're drawing in more electrons, so it's most likely the structure that follo...
Tue Nov 10, 2020 8:02 pm
Forum: Dipole Moments
Topic: London Dispersion forces
Replies: 7
Views: 31

### Re: London Dispersion forces

There aren't any exceptions as far as I know. I believe molecules/salts with larger molar mass and larger surface areas have bigger London Dispersion forces.
Sun Nov 08, 2020 1:21 pm
Forum: Lewis Structures
Topic: lewis structure
Replies: 10
Views: 62

### Re: lewis structure

Formal Charge = # of valence electrons - (shared electrons/2 + lone pairs). A short cut to this if you have the lewis structure drawn out is FC = VE - (number of lines + number of dots) since the lines represent the bonded electrons and the dots represent the lone electrons.
Sun Nov 08, 2020 12:57 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge of the Same Element
Replies: 15
Views: 45

### Re: Formal Charge of the Same Element

The formal charge of an element can vary, even within the same molecule. A great example of this is resonance structures, such as nitrite (NO2^-). In the lewis structure of nitrite, one of the oxygen has 3 lone pairs and a single bond with nitrogen, giving it a formal charge of -1. The other oxygen ...
Sun Nov 08, 2020 12:47 pm
Forum: Electronegativity
Topic: Lewis Acids and Bases (Sapling #6)
Replies: 4
Views: 39

### Re: Lewis Acids and Bases (Sapling #6)

Lewis acids accepts electron pairs. They're more likely to have a positive charge. The central atom in Lewis acids tend to have no lone pairs. Lewis bases donate electron pairs. They tend to have a negative charge. The central atom in Lewis bases tend to have lone pairs that are donated to Lewis aci...
Sun Nov 08, 2020 12:35 pm
Forum: Resonance Structures
Topic: Rules for Determining Favored Structure
Replies: 8
Views: 32

### Re: Rules for Determining Favored Structure

The favored resonance structure should have the lowest formal charge. If two resonance structures have the same formal charge, choose the structure where the negative formal charge is on the more electronegative element.
Sun Nov 08, 2020 12:24 pm
Forum: Resonance Structures
Topic: Oxidation Number
Replies: 9
Views: 47

### Re: Oxidation Number

To add on, for polyatomic ions, the sum of oxidation numbers should equal the charge of the ion. For example, in sulfate (SO4^2-), we know that the sum of the oxidation numbers should equal -2 and that the oxidation number for O is -2. We can get the equation X +4(-2) = -2 where X equals the oxidati...
Sun Nov 01, 2020 4:17 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent Bonds
Replies: 9
Views: 50

### Re: Covalent Bonds

Within the context of this class, covalent bonds are generally stronger than ionic bonds, but it can depend on the environment. For example, within a solution, ionic bonds are weaker than covalent bonds. Since many of the chemical reactions in biology involve solutions, we consider covalent bonds to...
Sun Nov 01, 2020 3:44 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Sapling HW Q17
Replies: 18
Views: 102

### Re: Sapling HW Q17

As you go across a period, atomic radius decreases since effective nuclear charge increases. The increased attraction between the protons and electrons leads to the electrons being drawn in closer to the nucleus, decreasing atomic radius. As you go down a group, atomic radius increases due to the in...
Sun Nov 01, 2020 3:30 pm
Forum: Trends in The Periodic Table
Replies: 30
Views: 348

Atomic radius decreases as you go across a period due to increasing nuclear charge. The stronger nuclear charge leads to an increased attraction between the positively charged protons in the nucleus and negatively charged electrons surrounding it. This leads to the electrons, including the valence e...
Sun Nov 01, 2020 3:20 pm
Forum: Trends in The Periodic Table
Topic: Oxygen and Ionization Energy
Replies: 9
Views: 39

### Re: Oxygen and Ionization Energy

I believe oxygen has a lower ionization energy compared to nitrogen due to increased electron electron repulsion within the orbital. For nitrogen, there's 1 electron in the 3 orbitals of the 2 p subshell. However, in oxygen there's suddenly 2 electrons in one of the orbitals, which increases electro...
Sun Nov 01, 2020 2:57 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbital vs. Subshell
Replies: 13
Views: 69

### Re: Orbital vs. Subshell

Each subshell has 1 or more or orbitals. Within an orbital, there's a high probability that an electron can be found. Also depending on the type of subshell, the number and shape of orbitals changes. (s subshells have 1 orbital, p subshells have 3 orbitals, d subshells have 5 orbitals, and f subshel...
Thu Oct 22, 2020 10:25 pm
Forum: SI Units, Unit Conversions
Topic: SI Conversions
Replies: 11
Views: 80

### Re: SI Conversions

To be on the safe side, it's probably best to memorize the more common conversions. One trick is to memorize the prefixes! (ex. kilo detonates 1000x, so 1 km = 1000m and 1 kg = 1000g). There's also angstrom, which represents 10^-10.
Thu Oct 22, 2020 10:14 pm
Forum: Significant Figures
Topic: Midterm
Replies: 9
Views: 81

### Re: Midterm

Not 100% sure, but even if there isn't a question dedicated to it, I imagine that we could get points docked off if our answers don't have the correct number of sig figs.
Thu Oct 22, 2020 10:04 pm
Forum: Limiting Reactant Calculations
Topic: General Limiting Question
Replies: 6
Views: 44

### Re: General Limiting Question

Yup, since the limiting reactant will run out first, it determines how much product will be created. It's possible that less product will form than expected in an actual experiment though due to factors such as the reactants sticking to the side of the tubes and not properly reacting.
Thu Oct 22, 2020 9:56 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Replies: 92
Views: 1960

I find the questions from the textbook and the step-up sessions very useful! I would also recommend writing down all the important formulas on a piece of paper and the memorizing and understanding the formulas. I think we will be given a formula sheet (maybe?), but flipping back and forth between pa...
Thu Oct 22, 2020 9:46 pm
Forum: Student Social/Study Group
Topic: Midterm Fundamentals Review Sheet
Replies: 7
Views: 67

### Re: Midterm Fundamentals Review Sheet

This looks super helpful! Thank you so much!! (Side note but your handwriting is so nice ;-;)
Sun Oct 18, 2020 7:39 pm
Forum: Properties of Light
Topic: energy level transfer
Replies: 7
Views: 35

### Re: energy level transfer

I think based off the equation E=-(hR)/n^2, E and n have an inverse relationship (As n increases, E will decrease. As n decreases, E will increase). So as n gets larger and larger and eventually approaches infinity, E will get smaller and smaller to the point where it is so minuscule, that it's appr...
Sun Oct 18, 2020 7:26 pm
Forum: Photoelectric Effect
Topic: Light Intensity
Replies: 23
Views: 97

### Re: Light Intensity

Yup! The number of photons increases when the brightness increases, but the wavelength/frequency of each photon remains the same. If the wavelength/frequency changed, then that could've changed what type of EM wave it was instead (ex. from visible light to UV light if the frequency increased/wavelen...
Sun Oct 18, 2020 7:12 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Exam Format
Replies: 14
Views: 89

### Re: Midterm Exam Format

Yes, all multiple choice. According to my TA, they're going to try to give partial credit, but I'm not exactly sure how.
Sun Oct 18, 2020 7:08 pm
Forum: Administrative Questions and Class Announcements
Topic: Built-in webcams/Equipment request [ENDORSED]
Replies: 22
Views: 710

### Re: Built-in webcams/Equipment request[ENDORSED]

I think it could depend on your TA. Mine is allowing us to use our phone or tablet as an external camera.
Sun Oct 18, 2020 7:04 pm
Forum: Administrative Questions and Class Announcements
Topic: UCLA Store Updates on Ebook/Sapling access card
Replies: 16
Views: 134

### Re: UCLA Store Updates on Ebook/Sapling access card

I placed my order around the end of week 0, and I still haven't received it in the mail. According to the store, my order has been shipped though, so I hope it'll arrive soon. I'll probably email them soon for a code.
Mon Oct 05, 2020 8:49 pm
Forum: Balancing Chemical Reactions
Topic: Stoichiometric Coefficients
Replies: 20
Views: 143

### Re: Stoichiometric Coefficients

I would say it's best to check because better safe than sorry! I've had so many instances where I forgot to check in the beginning and had to redo all the calculations. It ends up saving lots of time in the long run!
Mon Oct 05, 2020 8:38 pm
Forum: Molarity, Solutions, Dilutions
Topic: Mol VS Mole
Replies: 17
Views: 204

### Re: Mol VS Mole

Yup, mol is just a shorthand for mole! Unfortunately mol almost looks like an abbreviation for molecule (which I've seen abbreviated as mlcl before).
Mon Oct 05, 2020 8:22 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Determining Molar Mass
Replies: 19
Views: 207

### Re: Determining Molar Mass

It probably wouldn't make a significant difference in most cases, but if you want to be on the safe side use 15.999.
Mon Oct 05, 2020 8:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 226
Views: 116479

### Re: Advice from a Medical Student[ENDORSED]

Thank you so much for your advice! I'll try to take more notes during lecture from now on!