Search found 17668 matches

by Chem_Mod
Wed Nov 20, 2019 9:36 pm
Forum: Bond Lengths & Energies
Topic: Melting Points
Replies: 1
Views: 13

Melting Points

Just for clarification purposes, higher the intermolecular bond strength, higher will be the melting point. This is because you want to break the intermolecular forces within the solid. So higher bond strengths will require more energy to break the bonds, thus will have a higher melting point. There...
by Chem_Mod
Wed Nov 20, 2019 9:16 am
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 147
Views: 84070

Re: Advice from a Medical Student [ENDORSED]

Can you take all your medical school pre-requisites online or at a community college? If so, is it any less competitive? You can take them wherever you would like. I'm not sure if they accept online courses (that you would need to check with specific schools), but they should accept courses taken a...
by Chem_Mod
Wed Nov 20, 2019 9:11 am
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 147
Views: 84070

Re: Advice from a Medical Student [ENDORSED]

Is there a way to go to medical school without the pre-requisites such as chemistry classes and physics classes? Unfortunately, you cannot. You need to take these courses because medical school will only build on this material. They don't teach the foundations; they just assume you know it from the...
by Chem_Mod
Wed Nov 20, 2019 9:10 am
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 147
Views: 84070

Re: Advice from a Medical Student [ENDORSED]

Is there any way to complete medical school pre-requisites while majoring in business economics? Is this a smart move? What do you recommend for an indecisive individual? If you aren't a pre-med, I find that super cool! You end up becoming such a well-rounded applicant and I know from experience th...
by Chem_Mod
Wed Nov 20, 2019 9:08 am
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 147
Views: 84070

Re: Advice from a Medical Student [ENDORSED]

If you are not enjoying this class or subject but still have dreams of becoming a doctor, what do you do? Do you just go through it and hope it gets better? If it's a course that is a medical pre-requisite then you need to determine if being a doctor is still what you want to be. Medical school wit...
by Chem_Mod
Tue Nov 19, 2019 1:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar and Nonpolar Question [ENDORSED]
Replies: 4
Views: 840

Re: Polar and Nonpolar Question [ENDORSED]

You are welcome. :-)
by Chem_Mod
Mon Nov 18, 2019 7:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar and Nonpolar Question [ENDORSED]
Replies: 4
Views: 840

Re: Polar and Nonpolar Question [ENDORSED]

CH 2 Cl 2 is polar because it is tetrahedral. The only time a tetrahedral carbon is non-polar is when all 4 atoms connected to the central carbon atom are the same. I did this example in detail in class: CH 4 and CF 4 are non-polar as all the dipoles cancel. I also did variations of CH 3 Cl and disc...
by Chem_Mod
Mon Nov 18, 2019 7:19 pm
Forum: Lewis Structures
Topic: Curiosity [ENDORSED]
Replies: 6
Views: 664

Re: Curiosity [ENDORSED]

Selenic acid is an inorganic compound with the formula H2SeO4.

Here is the structure:
Selenic Acid.jpg
Selenic Acid.jpg (3.79 KiB) Viewed 618 times


In class, when I do more acids and bases, this Lewis structure will be straight forward after I discuss oxoacids.
by Chem_Mod
Mon Nov 18, 2019 3:43 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: dipole dipole
Replies: 4
Views: 22

Re: dipole dipole

Yes, dipole is permanent and is due to a difference in electronegativity between atoms forming a polar molecule.
by Chem_Mod
Mon Nov 18, 2019 3:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2 VSEPR's
Replies: 2
Views: 7

Re: 2 VSEPR's

No, there is only one VSEPR model per molecule.
by Chem_Mod
Mon Nov 18, 2019 3:28 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: London dispersion
Replies: 4
Views: 18

Re: London dispersion

A greater partial charge due to a greater amount of electrons/larger atomic radius.
by Chem_Mod
Mon Nov 18, 2019 3:26 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: IM Forces
Replies: 3
Views: 16

Re: IM Forces

Yes, because london forces are due to random fluctuations of electron density where there is an unequal distribution of electrons on one side of a molecule. All molecules are subject to this random fluctuation.
by Chem_Mod
Mon Nov 18, 2019 3:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.25a
Replies: 1
Views: 10

Re: 2E.25a

This has to do with the three dimensional structure of the molecule. CH2Cl2 is tetrahedral, therefore you cannot draw the Cl opposite to one another. It is difficult to see this when you draw the tetrahedral structure one dimensionally but if you look at a video of a tetrahedral molecule you'll see ...
by Chem_Mod
Mon Nov 18, 2019 3:11 pm
Forum: Hybridization
Topic: 2F.15
Replies: 1
Views: 12

Re: 2F.15

When referring to the s-character of a hybrid orbital, we look at the percent composition of the hybrid orbital in terms of s and p. For example, an sp3 hybrid orbital has 25% s-character because 1 of the 4 orbitals mixed is an s-orbital. Similarly, an sp2 hybrid orbital has 33% s-character. Hopeful...
by Chem_Mod
Mon Nov 18, 2019 3:08 pm
Forum: Hybridization
Topic: Normalized and Unnormalized
Replies: 1
Views: 30

Re: Normalized and Unnormalized

Do you mean hybridized vs unhybridized orbitals? There is no normalized and unnormalized vocabulary regarding hybridization.
by Chem_Mod
Mon Nov 18, 2019 3:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Density Isosurface and Electrostatic Potential Surface
Replies: 1
Views: 30

Re: Density Isosurface and Electrostatic Potential Surface

Density isosurface shows electron density that is the same (electron density isosurface) and plots electron density at a particular level. Iso means the same Electrostatic potential surface is different in that it shows electric fields representing a partial positive surface or a partial negative su...
by Chem_Mod
Mon Nov 18, 2019 3:02 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: 3F.5
Replies: 2
Views: 25

Re: 3F.5

Look at the strength of the intermolecular forces. NaCl is an ionic salt, it thus experiences ion-ion attractions between Na and Cl ions. Ion-ion forces are the strongest, therefore, NaCl will have the higher melting point. HCl is not an ionic compound; the strongest IMF between its molecules are di...
by Chem_Mod
Mon Nov 18, 2019 3:02 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: CH2Cl2
Replies: 3
Views: 18

Re: CH2Cl2

When drawing lewis structures, the arrangement in that case does not matter because everything is attached to the Carbon. Remember that the real structure is 3 dimensional, so any 2 dimensional drawing should be fine.
by Chem_Mod
Mon Nov 18, 2019 3:00 pm
Forum: Sigma & Pi Bonds
Topic: Orbitals in sigma and pi bonds
Replies: 1
Views: 12

Re: Orbitals in sigma and pi bonds

You want to think of sigma and pi bonds more in terms of molecular orbital hybridization theory. Sigma bonds will generally form between s or spx or spxdx orbitals, where x is an integer. Pi bonds generally form between overlapping p orbitals that are not hybridized
by Chem_Mod
Mon Nov 18, 2019 11:28 am
Forum: Determining Molecular Shape (VSEPR)
Topic: What are the names of the geometries that we must know? [ENDORSED]
Replies: 3
Views: 30

Re: What are the names of the geometries that we must know? [ENDORSED]

Multiple VSEPR charts have been posted on Chemistry Community.
by Chem_Mod
Mon Nov 18, 2019 10:31 am
Forum: Administrative Questions and Class Announcements
Topic: KAREN SUN 5-7PM WORKSHOP - DOWNLAOD WORKSHEETS HERE
Replies: 49
Views: 1449

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

Here are the answers to the worksheet from last night. The worksheet is a little ahead of class material as to not fall behind during Thanksgiving break where we will have no session. Test 2 will cover material after the midterm and up to the first 5 minutes of today (Monday) lecture.
by Chem_Mod
Sun Nov 17, 2019 9:10 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: induced dipole
Replies: 4
Views: 11

Re: induced dipole

In addition to the examples listed here, there are induced dipole-induced dipole interactions between two nonpolar molecules. This arises from a temporary dipole moment in a nonpolar molecule resulting from random uneven electron distribution, which in turn can induce another temporary dipole in a n...
by Chem_Mod
Sun Nov 17, 2019 8:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E. 25 Polar molecules
Replies: 1
Views: 21

Re: 2E. 25 Polar molecules

You have to take into account the 3D molecular geometry instead of just looking at the 2D Lewis structure. A carbon with 4 bonds is tetrahedral, so all the positions of the atoms are all equivalent at approximately 109.5 degrees away from each other. So there is not cis or trans isomer for tetrahedr...
by Chem_Mod
Sun Nov 17, 2019 8:51 pm
Forum: Dipole Moments
Topic: Cancelling dipole moments
Replies: 7
Views: 42

Re: Cancelling dipole moments

You can first relate it to its structure, which is a tetrahedral. Since there are two chlorine atoms on opposite sides of each other, the two dipole moments will cancel each other out. However, since there is a third chlorine atom, that dipole moment will not be cancelled out, meaning that there is...
by Chem_Mod
Sun Nov 17, 2019 8:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Same Molecular Formula, Different Shape
Replies: 2
Views: 11

Re: Same Molecular Formula, Different Shape

The molecular formula does not always give you the exact molecular shape, as shape depends on the location of bonding and lone pairs of electrons. This is especially true with organic compounds, where multiple molecules have the same molecular formula (number of each atom). This is why in problems, ...
by Chem_Mod
Sat Nov 16, 2019 3:13 pm
Forum: Administrative Questions and Class Announcements
Topic: Worksheet for 1D/1F 10/16
Replies: 17
Views: 779

Re: Worksheet for 1D/1F 10/16

Answer key for test 2 problems
by Chem_Mod
Sat Nov 16, 2019 3:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Worksheet for 1D/1F 10/16
Replies: 17
Views: 779

Re: Worksheet for 1D/1F 10/16

Here are some practice problems for test 2 for you to enjoy your weekend with, mostly focusing on geometry/bond angle stuff.
by Chem_Mod
Sat Nov 16, 2019 12:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone pairs
Replies: 3
Views: 15

Re: Lone pairs

Correct; to expand on that, bonding pair electrons are more restricted in their domain because they experience attractive forces from both atom's nuclei, so are localized between the two nuclei. Lone pairs only experience attraction from one atom's nuclei, so they are not pulled as tightly. Therefor...
by Chem_Mod
Sat Nov 16, 2019 12:32 pm
Forum: Dipole Moments
Topic: Dipole-Dipole vs. Dipole-Induced Dipole
Replies: 3
Views: 14

Re: Dipole-Dipole vs. Dipole-Induced Dipole

A dipole-dipole force involves two permanent dipole moments, so typically between two polar bonds. On the other hand, a dipole-induced dipole force involves a permanent dipole moment inducing, or causing, a temporary dipole moment on another bond that was not there before the interaction, so typical...
by Chem_Mod
Sat Nov 16, 2019 12:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 3
Views: 19

Re: Bond Angles

Not necessarily. All bonds, regardless of multiplicity (e.g. single bond, double bond) or polarity, all have the same amount of electron repulsion because they are all confined to the spaces between atoms. However, lone pairs cause more electron repulsion because they are not bonded to anything and ...
by Chem_Mod
Fri Nov 15, 2019 7:00 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: Hydrogen Peroxide IMF
Replies: 1
Views: 22

Re: Hydrogen Peroxide IMF

Because of the lone pairs on H2O2 the shape will always be bent (regardless if they are drawn linear in a lewis structure). Since a lone pair is required on N, O, or F molecules to form hydrogen bonds, they are typically nonlinear.
by Chem_Mod
Fri Nov 15, 2019 6:56 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: Would SO4 and H2O be dipole-induced dipole or dipole-dipole
Replies: 1
Views: 21

Re: Would SO4 and H2O be dipole-induced dipole or dipole-dipole

Since SO4 exists as SO42- this is actually a case of ion-dipole interaction. An example of dipole-induced dipole would be between CCl4 and water
by Chem_Mod
Fri Nov 15, 2019 6:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Problem 2E.19
Replies: 1
Views: 24

Re: Problem 2E.19

For deciding which atom is the central atom, a good rule to go by is choosing the element with the lowest ionization energy as the central atom. For (a) S has a lower ionization energy compared to O and for (b), Be would be at the center since it has the lower ionization energy. From there, symmetry...
by Chem_Mod
Fri Nov 15, 2019 6:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: C2H4
Replies: 3
Views: 22

Re: C2H4

Since C2H4 has a carbon with a double bond and two hydrogen molecules one each side, there are no lone pairs on carbon. Therefore, each carbon will have a trigonal planar shape meaning the H-C-H bond angle will be 120 degrees and the H-C-C will also be 120 degrees.
by Chem_Mod
Fri Nov 15, 2019 5:19 pm
Forum: Administrative Questions and Class Announcements
Topic: F19 WEEK 7 1k
Replies: 1
Views: 64

Re: F19 WEEK 7 1k

Hope this was helpful.
by Chem_Mod
Fri Nov 15, 2019 5:19 pm
Forum: Administrative Questions and Class Announcements
Topic: F19 week 7 1a
Replies: 1
Views: 111

Re: F19 week 7 1a

Hope this was helpful.
by Chem_Mod
Fri Nov 15, 2019 5:18 pm
Forum: Administrative Questions and Class Announcements
Topic: F19 week 6 1k
Replies: 1
Views: 129

Re: F19 week 6 1k

Hope this was helpful.
by Chem_Mod
Fri Nov 15, 2019 5:17 pm
Forum: Administrative Questions and Class Announcements
Topic: CHEM 14A Section 4B/1H VSEPR Additional Resources
Replies: 2
Views: 80

Re: CHEM 14A Section 4B/1H VSEPR Additional Resources

Use Sapling as it has many great problems as assignments.
by Chem_Mod
Fri Nov 15, 2019 3:30 pm
Forum: Administrative Questions and Class Announcements
Topic: CHEM 14A Section 4B/1H VSEPR Additional Resources
Replies: 2
Views: 80

CHEM 14A Section 4B/1H VSEPR Additional Resources

Hi scholars, I wanted to share a great resource that I helped contribute to during my time at UC Davis. The following is a link to Chemistry Libre Text, which is like a Wikipedia page for all topics chemistry. This particular link is for the page that goes over VSEPR geometry, bond angles, lone pair...
by Chem_Mod
Thu Nov 14, 2019 3:11 pm
Forum: Administrative Questions and Class Announcements
Topic: some VSPER resources
Replies: 1
Views: 151

some VSPER resources

Hi! I have attached a word doc with some helpful links / homework problems!

Julia
by Chem_Mod
Thu Nov 14, 2019 8:58 am
Forum: Administrative Questions and Class Announcements
Topic: Worksheet for 1D/1F 10/16
Replies: 17
Views: 779

Re: Worksheet for 1D/1F 10/16

Answer key
by Chem_Mod
Thu Nov 14, 2019 8:26 am
Forum: Administrative Questions and Class Announcements
Topic: F19 WEEK 7 1k
Replies: 1
Views: 64

F19 WEEK 7 1k

F19 WEEK 7 1k
by Chem_Mod
Wed Nov 13, 2019 10:30 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Intermolecular Forces
Replies: 2
Views: 14

Re: Intermolecular Forces

Draw the lewis structure first, if you can identify a dipole (difference in electronegativity between two atoms), it will have dipole dipole interactions and dipole - induced dipole, especially if another molecule that has no dipole is present (induced). If it does not have those properties, then th...
by Chem_Mod
Wed Nov 13, 2019 10:23 am
Forum: Dipole Moments
Topic: 3F.1
Replies: 2
Views: 28

Re: 3F.1

All molecules have london forces to a certain extent, those that have a dipole will have dipole - dipole interactions in addition to the already present london dispersion forces. The N - H bonds have a dipole pointed towards the nitrogen, and the O - H bonds have a dipole pointed towards to the oxyg...
by Chem_Mod
Wed Nov 13, 2019 10:20 am
Forum: Dipole Moments
Topic: 3F. 7
Replies: 1
Views: 13

Re: 3F. 7

SO2 should have a higher boiling point as it will have dipole interactions, whereas O3 will only have induced dipole. Dipole interactions are stronger than induced dipole.
by Chem_Mod
Wed Nov 13, 2019 9:22 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: Determining Polarity
Replies: 5
Views: 39

Re: Determining Polarity

There a few different cutoffs. Using the pauling scale of electronegativity (link below), generally we can say if the difference in electronegativity is about 0.5 or greater we can say it's a polar bond and the molecule may be polar. If it's greater than 1.5 - 2 or greater, it becomes ionic. However...
by Chem_Mod
Wed Nov 13, 2019 9:13 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: Molecule Size and Melting Points
Replies: 6
Views: 17

Re: Molecule Size and Melting Points

Yes, if molecules have the same general structure, then the bigger one or one with more molecular weight will have the higher boiling or melting point.
by Chem_Mod
Wed Nov 13, 2019 9:08 am
Forum: Administrative Questions and Class Announcements
Topic: Worksheet for 1D/1F 10/16
Replies: 17
Views: 779

Re: Worksheet for 1D/1F 10/16

Chem_Mod wrote:Here's this week's worksheet. Answer key will be posted after discussion tomorrow.


Question 6 should ask "why does nitrogen to carbon bond not freely rotate?" You may think of sp3 hydbridized atoms as having only single bonds, and sp2 hybridized atoms as having a double bond.
by Chem_Mod
Tue Nov 12, 2019 9:31 pm
Forum: Administrative Questions and Class Announcements
Topic: Worksheet for 1D/1F 10/16
Replies: 17
Views: 779

Re: Worksheet for 1D/1F 10/16

Here's this week's worksheet. Answer key will be posted after discussion tomorrow.
by Chem_Mod
Tue Nov 12, 2019 6:41 am
Forum: Administrative Questions and Class Announcements
Topic: F19 week 7 1a
Replies: 1
Views: 111

F19 week 7 1a

! week 7 1a
by Chem_Mod
Mon Nov 11, 2019 3:24 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: hydrogen bonding
Replies: 1
Views: 16

Re: hydrogen bonding

Diethyl ether is not capable of hydrogen bonding. If you draw the lewis structure, the oxygen is bonded to the carbons of two ethyl groups (abbreviated as C2H5 or CH3CH2), not the hydrogens. For hydrogen bonding to occur, there must be a hydrogen directly bonded to an O, N, or F, which is not the ca...
by Chem_Mod
Mon Nov 11, 2019 3:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polar bonds and molecular shape
Replies: 2
Views: 16

Re: polar bonds and molecular shape

Polar bonds do not affect molecular shape. However, molecular shape does affect the polarity of a molecule when there are polar bonds. Since we can think of dipole moments as vectors, if they do not cancel based on the shape of the molecule, then the molecule will be polar. If they do cancel, then t...
by Chem_Mod
Sun Nov 10, 2019 8:26 am
Forum: Administrative Questions and Class Announcements
Topic: KAREN SUN 5-7PM WORKSHOP - DOWNLAOD WORKSHEETS HERE
Replies: 49
Views: 1449

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

Since you all had your midterm on Wednesday, there is not too much material to review this weekend. Today's workshop will be a drop-in where you can bring in questions about past material or homework. Have a great 3-day weekend!

-Karen
by Chem_Mod
Fri Nov 08, 2019 6:01 pm
Forum: Dipole Moments
Topic: Hydrogen Bonds
Replies: 6
Views: 24

Re: Hydrogen Bonds

Because they have some covalent character.
by Chem_Mod
Fri Nov 08, 2019 5:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Reference Table for VSEPR
Replies: 3
Views: 31

Re: Reference Table for VSEPR

Search Chemistry Community. Several have been posted.

Figure 2E.1 is lists the shapes, names, and clear visual examples.
by Chem_Mod
Fri Nov 08, 2019 6:14 am
Forum: Administrative Questions and Class Announcements
Topic: F19 week 6 1k
Replies: 1
Views: 129

F19 week 6 1k

discussion worksheet
by Chem_Mod
Thu Nov 07, 2019 12:59 pm
Forum: Resonance Structures
Topic: Resonance structures for (NH2)COCH3 [ENDORSED]
Replies: 1
Views: 57

Re: Resonance structures for (NH2)COCH3 [ENDORSED]

Hello, the key doesn't have a radical as a resonance structure. A radical is when you have one lone pair electron that is not paired with another one. The resonance structure provided in the key has a separation of charge where one atom has a formal charge of +1 and one -1, but this does not make it...
by Chem_Mod
Wed Nov 06, 2019 11:18 pm
Forum: DeBroglie Equation
Topic: Week 3 Lyndon's Workshop
Replies: 1
Views: 81

Re: Week 3 Lyndon's Workshop

You can always try to get answers at future sessions!
by Chem_Mod
Wed Nov 06, 2019 10:57 pm
Forum: Bond Lengths & Energies
Topic: Test 2 Topics
Replies: 40
Views: 218

Re: Test 2 Topics

Topics covered from the midterm to test 2.
by Chem_Mod
Wed Nov 06, 2019 10:55 pm
Forum: Student Social/Study Group
Topic: Class Grading
Replies: 21
Views: 154

Re: Class Grading

correct
by Chem_Mod
Wed Nov 06, 2019 6:45 pm
Forum: Electronegativity
Topic: Website
Replies: 3
Views: 52

Re: Website

It is working fine.
by Chem_Mod
Wed Nov 06, 2019 2:45 pm
Forum: Administrative Questions and Class Announcements
Topic: Worksheet for 1D/1F 10/16
Replies: 17
Views: 779

Re: Worksheet for 1D/1F 10/16

Chem_Mod wrote:Rip, sorry forgot to post the answer key yesterday

There's an error for number one, the highest frequency is i but the highest wavelength is iiii.
by Chem_Mod
Wed Nov 06, 2019 2:44 pm
Forum: Administrative Questions and Class Announcements
Topic: Worksheet for 1D/1F 10/16
Replies: 17
Views: 779

Re: Worksheet for 1D/1F 10/16

For number 4 part b on the extra practice problems, why doesn't boron have to complete it's octet? In your answer key, boron only has 6 electrons accounted for in the lewis structure Boron's a weird one where giving it an octet would require it have a negative one charge or greater. Since it is not...
by Chem_Mod
Wed Nov 06, 2019 10:18 am
Forum: Administrative Questions and Class Announcements
Topic: Solution Manuel
Replies: 1
Views: 36

Re: Solution Manuel

Wish there was. I have asked the publisher to offer this.
by Chem_Mod
Wed Nov 06, 2019 10:15 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic vs molecular spectroscopy: outline 2 [ENDORSED]
Replies: 1
Views: 41

Re: Atomic vs molecular spectroscopy: outline 2 [ENDORSED]

Electrons in atoms can be excited to higher atomic orbitals.
Electrons in molecules can be excited to higher molecular orbitals.

The energy difference for the above transitions typically occur in the visible and UV region.
by Chem_Mod
Wed Nov 06, 2019 10:10 am
Forum: General Science Questions
Topic: Schrodinger's Equation [ENDORSED]
Replies: 1
Views: 49

Re: Schrodinger's Equation [ENDORSED]

Valid solutions from Schrodinger's equation give wave functions, psi, that give the energy, E, of the electron (that the wave function is modelling).
These valid wave functions (math functions) are orbitals.

As discussed in class, students need to know where 'orbitals' come from.
by Chem_Mod
Wed Nov 06, 2019 10:08 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Schrodingers eq [ENDORSED]
Replies: 1
Views: 48

Re: Schrodingers eq [ENDORSED]

Valid solutions from Schrodinger's equation give wave functions, psi, that give the energy, E, of the electron (that the wave function is modelling).
These valid wave functions (math functions) are orbitals.

As discussed in class, students need to know where 'orbitals' come from.
by Chem_Mod
Wed Nov 06, 2019 10:07 am
Forum: *Shrodinger Equation
Topic: Shrodinger Equation Relationships? [ENDORSED]
Replies: 1
Views: 72

Re: Shrodinger Equation Relationships? [ENDORSED]

Valid solutions from Schrodinger's equation give wave functions, psi, that give the energy, E, of the electron (that the wave function is modelling).
These valid wave functions (math functions) are orbitals.
by Chem_Mod
Wed Nov 06, 2019 9:52 am
Forum: Administrative Questions and Class Announcements
Topic: Worksheet for 1D/1F 10/16
Replies: 17
Views: 779

Re: Worksheet for 1D/1F 10/16

Rip, sorry forgot to post the answer key yesterday
by Chem_Mod
Tue Nov 05, 2019 4:18 pm
Forum: Ionic & Covalent Bonds
Topic: Lattice Energy [ENDORSED]
Replies: 2
Views: 546

Re: Lattice Energy [ENDORSED]

I concur.

Unless you really, really want it on the midterm … :-(
by Chem_Mod
Tue Nov 05, 2019 4:15 pm
Forum: Administrative Questions and Class Announcements
Topic: For the midterm will we need to know how to do electron configurations for the f shell? [ENDORSED]
Replies: 2
Views: 583

Re: For the midterm will we need to know how to do electron configurations for the f shell? [ENDORSED]

As I discussed several times in class, the f-block elements are not covered in general chemistry.

In class we discussed the visible and UV regions several times so they should be known.
by Chem_Mod
Tue Nov 05, 2019 4:10 pm
Forum: Bond Lengths & Energies
Topic: Coordination compounds [ENDORSED]
Replies: 1
Views: 661

Re: Coordination compounds [ENDORSED]

I have not yet covered coordination compounds.
I don't think students would want it …
by Chem_Mod
Tue Nov 05, 2019 12:08 pm
Forum: Administrative Questions and Class Announcements
Topic: Worksheet for 1D/1F 10/16
Replies: 17
Views: 779

Re: Worksheet for 1D/1F 10/16

Here's the worksheet, answer key coming soon!
by Chem_Mod
Mon Nov 04, 2019 3:24 pm
Forum: Coordinate Covalent Bonds
Topic: Coordinate Covalent Bonds
Replies: 1
Views: 53

Re: Coordinate Covalent Bonds

Coordinate covalent bonds are when a bond is formed from a lone pair from only ONE atom donating BOTH electrons. Remember a bond is two electrons. Take for example NH3 and BF3 bonding to NH3BF3. The bond between the N and B comes from the two electrons from the N, not 1 from N and 1 from B.
by Chem_Mod
Mon Nov 04, 2019 3:23 pm
Forum: Molarity, Solutions, Dilutions
Topic: Textbook question
Replies: 3
Views: 56

Re: Textbook question

I'm assuming c is concentration (ie Molarity), M is also molarity, n= number of moles, and v= volume. Can you elaborate on what "m" refers to?
by Chem_Mod
Mon Nov 04, 2019 3:21 pm
Forum: Ionic & Covalent Bonds
Topic: Melting points of ionic substances
Replies: 1
Views: 39

Re: Melting points of ionic substances

The strength of the interactions between the anion and cation, which can be determined by electronegativity differences as well as atomic radius. As eneg difference increases and atomic radius decreases, melting point increases.
by Chem_Mod
Mon Nov 04, 2019 3:21 pm
Forum: Lewis Structures
Topic: CH3CNO Resonance ???
Replies: 2
Views: 53

Re: CH3CNO Resonance ???

For further clarification: The two other resonance structures you mentioned are viable resonance structures; however they are what we call minor resonance contributors because they do not have the best formal charges assigned to the atoms. There is only one major (best) resonance contributor, which ...
by Chem_Mod
Mon Nov 04, 2019 3:18 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: 12 on workshop worksheet
Replies: 1
Views: 53

Re: 12 on workshop worksheet

You are correct in saying that B is more electronegative than C, and so the B-O should be more polar. The answer key is wrong, thank you for pointing that out! We will be sure to fix it.
by Chem_Mod
Mon Nov 04, 2019 3:18 pm
Forum: Ionic & Covalent Bonds
Topic: 2D.1
Replies: 2
Views: 31

Re: 2D.1

Because you only look at the number of protons when you are comparing two elements in the same row, however because selenium is in a higher row than the other three elements there is less shielding associated with it. Therefore, selenium's positively charged nucleus is able to attract electrons more...
by Chem_Mod
Mon Nov 04, 2019 3:15 pm
Forum: Lewis Structures
Topic: CH3CNO Resonance ???
Replies: 2
Views: 53

Re: CH3CNO Resonance ???

Electrons are constantly moving, resulting in formation of resonance structures when empty p orbitals are available. These other resonance structures are likely only minor contributors, as they are less stable than the main contributing structure. You will learn more about this and "arrow-pushi...
by Chem_Mod
Mon Nov 04, 2019 3:13 pm
Forum: Lewis Structures
Topic: Inorganic vs Organic vs Biological
Replies: 1
Views: 24

Re: Inorganic vs Organic vs Biological

The same principles for all Lewis structures applies, using formal charge, etc. to determine a reasonable structure.
Organic and Biological molecules normally have Carbon and Nitrogen elements.
by Chem_Mod
Mon Nov 04, 2019 3:12 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: 2D.5 - Electronegativity
Replies: 4
Views: 51

Re: 2D.5 - Electronegativity

In comparing electronegativity of two atoms it is important to think about their respective atomic radii. Oxygen is in the same column as S but it is higher, therefore it has less shielding and a smaller atomic radius. Because this is the case, oxygen's positively charged nucleus is able to attract ...
by Chem_Mod
Mon Nov 04, 2019 3:12 pm
Forum: General Science Questions
Topic: Chem 14 B and Chem 14 BL
Replies: 1
Views: 46

Re: Chem 14 B and Chem 14 BL

If you can get into 14BL next quarter then great. 14BL doesn't have to be taken along with 14B, you can take it later as well. It just depends on you, whatever you are more comfortable doing.
by Chem_Mod
Mon Nov 04, 2019 3:04 pm
Forum: Lewis Structures
Topic: How do I know when to use a double bond?
Replies: 7
Views: 44

Re: How do I know when to use a double bond?

Just kidding, remember the order of priorities. Make sure you have the correct number of electrons, then pay attention to the octet rule. After that, double bonds can be created to ensure you have the lowest energy lewis structure meaning fewest formal charges, and with any negative formal charges o...
by Chem_Mod
Mon Nov 04, 2019 3:03 pm
Forum: Lewis Structures
Topic: How do I know when to use a double bond?
Replies: 7
Views: 44

Re: How do I know when to use a double bond?

You just kinda know.
by Chem_Mod
Mon Nov 04, 2019 3:03 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Ionic and Covalent character
Replies: 2
Views: 31

Re: Ionic and Covalent character

These terms simply refer to the sharing of the two electrons that make up a bond between two atoms. Greater unequal sharing or distribution of electrons means greater ionic character and more equal sharing means more covalent character. It follows that when there is a greater electronegativity diffe...
by Chem_Mod
Mon Nov 04, 2019 1:19 pm
Forum: *Black Body Radiation
Topic: Midterm 1
Replies: 1
Views: 30

Re: Midterm 1

Black Body radiation is not part of the syllabus.
by Chem_Mod
Sun Nov 03, 2019 11:12 pm
Forum: Administrative Questions and Class Announcements
Topic: KAREN SUN 5-7PM WORKSHOP - DOWNLAOD WORKSHEETS HERE
Replies: 49
Views: 1449

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

If a certain frequency of radiation is not ejecting electrons from the surface of a metal, is it possible to eject electrons by increasing the intensity of the incident radiation? How would we solve a question such as the question stated above? Does the intensity refer to the wavelength of the radi...
by Chem_Mod
Sun Nov 03, 2019 11:10 pm
Forum: Administrative Questions and Class Announcements
Topic: DINO NUGGETS Review Session! Download Problems HERE [ENDORSED]
Replies: 52
Views: 3140

Re: DINO NUGGETS Review Session! Download Problems HERE [ENDORSED]

ayushibanerjee06 wrote:
Ada Chung 1C wrote:Will the mini dino nuggets answer key be posted as well?

Will they be posted? pls help us out

Posted :) Apologies for the wait.
by Chem_Mod
Sun Nov 03, 2019 11:02 pm
Forum: Dipole Moments
Topic: Calculating Dipole Moments
Replies: 1
Views: 17

Re: Calculating Dipole Moments

You won't need to calculate dipole moments but you will need to know how to identify if one exists (using relative electronegativities) and be able to draw the arrow and partial charges on the Lewis structure.
by Chem_Mod
Sun Nov 03, 2019 10:40 pm
Forum: Photoelectric Effect
Topic: Dino Nuggets 8a
Replies: 1
Views: 28

Re: Dino Nuggets 8a

We isolated frequency because the question asked to find the frequency of the light. It's generally good practice to manipulate the variables you are working with to isolate the one that you are solving for. This is more efficient but not necessary; if you don't feel comfortable doing that you can s...
by Chem_Mod
Sun Nov 03, 2019 10:21 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterms
Replies: 6
Views: 49

Re: Midterms

Yes, but there is also Test 2 after the midterm.
by Chem_Mod
Sun Nov 03, 2019 9:28 pm
Forum: Resonance Structures
Topic: Resonance hybrid vs resonance contributor
Replies: 1
Views: 17

Re: Resonance hybrid vs resonance contributor

The resonance hybrid is the blending of all possible resonance contributors and represents the true structure of the molecule.
by Chem_Mod
Sun Nov 03, 2019 10:03 am
Forum: Octet Exceptions
Topic: Tungsten Electronic Configuration [ENDORSED]
Replies: 2
Views: 22

Re: Tungsten Electronic Configuration [ENDORSED]

Thanks for answering this.

See my detailed answer here: viewtopic.php?f=23&t=47967&p=170473&hilit=tungsten&sid=0e5b17cc2a1046c645bd802eed503cad#p170473

I have removed part e of this problem as it is not part of the Chem 14A syllabus.
by Chem_Mod
Sun Nov 03, 2019 10:02 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E #13
Replies: 3
Views: 44

Re: 1E #13

See my detailed answer here: viewtopic.php?f=23&t=47967&p=170473&hilit=tungsten&sid=0e5b17cc2a1046c645bd802eed503cad#p170473

I have removed part e of this problem as it is not part of the Chem 14A syllabus.
by Chem_Mod
Sun Nov 03, 2019 10:01 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework Problem 1E.13
Replies: 3
Views: 25

Re: Homework Problem 1E.13

See my detailed answer here: viewtopic.php?f=23&t=47967&p=170473&hilit=tungsten&sid=0e5b17cc2a1046c645bd802eed503cad#p170473

I have removed part e of this problem as it is not part of the Chem 14A syllabus.

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