Search found 101 matches

by Sebastian Lee 1L
Tue Jan 14, 2020 9:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acids and Bases
Replies: 6
Views: 28

Re: Acids and Bases

Like others have said, acid and base reactions are not always at equilibrium. However, it is important to note that when we do calculations for pH, pK a , and pK b , these values will be based on equilibrium concentrations. This is especially important when considering weak acids/bases' dissociation...
by Sebastian Lee 1L
Tue Jan 14, 2020 2:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong Acids/Bases
Replies: 4
Views: 16

Re: Strong Acids/Bases

To add on to previous comments, since weak bases do not fully dissociate into their respective ions, you will have concentrations of both reactant and product at equilibrium. This is the basis for K a which is equal to the concentration of the dissociated products over the remaining concentration of...
by Sebastian Lee 1L
Mon Jan 13, 2020 9:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 5.39
Replies: 1
Views: 16

Re: Homework 5.39

I used the information in table 5G.2 to help figure the problem out. If you look at that table, you'll find the equilibrium constant for the reverse reaction ( N_{2}O_{4} (g) \rightleftharpoons 2NO_{2} (g) ) at 298 K. From here you should be able to figure out K for the given reactio...
by Sebastian Lee 1L
Mon Jan 13, 2020 7:51 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH range
Replies: 4
Views: 24

Re: pH range

Yes, it is indeed possible to have pH outside of the range from 0 to 14. For example, if you had a solution of 10M HCl (a strong acid), you would find the pH = -log(H+) to be -1. Of course, this would be a tremendously strong acid solution. Likewise for very strong bases, if you had a solution of 10...
by Sebastian Lee 1L
Mon Jan 13, 2020 7:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6A.21
Replies: 1
Views: 15

Re: 6A.21

To do this problem, you would use the same concept that we used when finding the concentration of H 3 O + and OH - at the normal room temperature of 25C. Remember that if the solution is neutral, that means that both concentrations of H 3 O + and OH - are equal. The problem gives us that K w is 2.1 ...
by Sebastian Lee 1L
Wed Jan 08, 2020 4:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc and Kp
Replies: 8
Views: 33

Re: Kc and Kp

when a question simply asks for "the equilibrium constant" or "K" does that mean related to concentration or pressure? and why is this so easily interchangeable? I believe that when a problem asks you to find the equilibrium constant, unless it specifies to find Kc or Kp, you sh...
by Sebastian Lee 1L
Wed Jan 08, 2020 4:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Are Both L and Aq Excluded From Equilibrium Constant Expressions?
Replies: 4
Views: 31

Re: Are Both L and Aq Excluded From Equilibrium Constant Expressions?

So, I know that solids and liquids are not supposed to be included in Kc but I was wondering if Aq is excluded as well. Isn’t Aq liquid too? Also, I still don’t really understand why these things are excluded from the expression so can someone please explain to me why. Aq is included in the equilib...
by Sebastian Lee 1L
Wed Jan 08, 2020 2:47 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Clarification on Q<K and R&P concentrations
Replies: 2
Views: 27

Clarification on Q<K and R&P concentrations

In lecture, Dr. Lavelle had on the slides that if Q<K, then [R]>[P] and the forward reaction is favored. I understand that when Q is less than K that means the ratio of products over reactants is less, signifying that there are more reactants (and less products) at that time than there would be at e...
by Sebastian Lee 1L
Wed Jan 08, 2020 2:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook question 5I.11
Replies: 1
Views: 24

Re: Textbook question 5I.11

Could someone please explain how to get part a? I keep getting 13.9 instead of 6.9 Alright I think I know where you went wrong. When you're finding the reaction quotient Q c for an equilibrium reaction with concentration you MUST make sure that you are using the correct concentrations. In the probl...
by Sebastian Lee 1L
Mon Jan 06, 2020 9:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Heterogeneous Equilibria
Replies: 2
Views: 24

Re: Heterogeneous Equilibria

For heterogeneous equilibria, you will use the same general equation to find the equilibrium constant as for homogeneous equilibria: K_{c}=\frac{[C]^c[D]^d}{[A]^a[B]^b} . However, in heterogeneous equilibria, you will NOT include any solids or pure liquids in the formula. I believe this is because t...
by Sebastian Lee 1L
Mon Jan 06, 2020 8:53 pm
Forum: Ideal Gases
Topic: Dynamic Equilibrium
Replies: 10
Views: 54

Re: Dynamic Equilibrium

I believe what is meant by dynamic equilibrium is that when a reaction is in equilibrium, there still are reactions occurring. It is not a static system. When a reaction is at equilibrium, concentrations of reactant and product are the same because the reactants are forming products at the same rate...
by Sebastian Lee 1L
Sat Dec 07, 2019 8:06 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Bond order
Replies: 2
Views: 29

Re: Bond order

I think bond order just means is it single, double, or triple bond. So the bond order for Cl2 is 1 since it's a single bond.
by Sebastian Lee 1L
Sat Dec 07, 2019 7:59 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: ph concept
Replies: 5
Views: 55

Re: ph concept

please quote my question so i get a notification, thanks in advance! i know there is something wrong with my thought process, but i cannot figure it out. my thought process is that if a base is weaker, less oh- will be dissociated out. taking the -log of that smaller number will result in a smaller...
by Sebastian Lee 1L
Sat Dec 07, 2019 7:36 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Oxoacid Strength
Replies: 6
Views: 45

Re: Oxoacid Strength

Yep, HOF is the stronger acid! When the acids dissociate and donate their proton, you will be left with the anions, FO - and ClO - . Since F is more electronegative it will be able to better delocalize the negative charge of the Oxygen by pulling the electrons closer to it. This delocalization/induc...
by Sebastian Lee 1L
Sat Dec 07, 2019 7:12 pm
Forum: Photoelectric Effect
Topic: Dino Nuggets question 8b
Replies: 3
Views: 69

Re: Dino Nuggets question 8b

For reference: 8b) A newly designed laser pointer with a certain frequency is pointed at a sodium metal surface. An electron is ejected from the metal surface with wavelength 1.10 nm. What is the frequency of the light from the laser pointer? The work function of sodium is 150.6 kJ∙mol-1. I'll just ...
by Sebastian Lee 1L
Sat Dec 07, 2019 6:55 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: determining number of hydrogen bonding sites
Replies: 3
Views: 39

Re: determining number of hydrogen bonding sites

Recall that hydrogen bonds can form when a hydrogen that is bonded to a Nitrogen, Oxygen, or Fluorine is strongly attracted to a Nitrogen, Oxygen, or Fluorine with a lone pair. In problems where it asks you to find how many hydrogen bonding sites there are, you should look for the hydrogens bonded t...
by Sebastian Lee 1L
Wed Dec 04, 2019 3:20 pm
Forum: Bronsted Acids & Bases
Topic: HOI vs HOCl
Replies: 3
Views: 21

Re: HOI vs HOCl

HOCl and HOI are both oxoacids and act quite differently, because of the oxygen involved in their structure. Since the electrons are withdrawn (or pulled due to the high electronegativity of oxygen and chlorine), they are delocalized and are more prone to get rid of the H+ proton than HOI. But when...
by Sebastian Lee 1L
Wed Dec 04, 2019 3:05 pm
Forum: Conjugate Acids & Bases
Topic: Conjugate Acids and Bases (Uses)
Replies: 1
Views: 16

Re: Conjugate Acids and Bases (Uses)

I think we should know conjugate acids/bases because they are related to the strength of acids/bases and how salts can or cannot affect pH of a solution. The conjugate base of an acid is basically the product once the acid donates the proton (assuming Bronsted acid). For example, the conjugate base ...
by Sebastian Lee 1L
Wed Dec 04, 2019 2:48 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: intermolecular energy equation
Replies: 1
Views: 16

Re: intermolecular energy equation

The interaction potential energy equation says that the energy/strength of an intermolecular force is directly proportional to the polarizability of the two molecules and inversely proportional to the distance between them. You don't need to do any calculations with this but you should be able to co...
by Sebastian Lee 1L
Tue Dec 03, 2019 10:54 am
Forum: Conjugate Acids & Bases
Topic: conjugate base and pH
Replies: 4
Views: 38

Re: conjugate base and pH

The conjugate base of a strong acid will not affect the pH because it is weak and stable. For example, if you have a Cl- anion in a salt, that is the conjugate base of HCl, a strong acid. Remember that strong acids will completely dissociate into ions so for HCl: HCl\rightarrow H^{+} + Cl^{-} . Cl- ...
by Sebastian Lee 1L
Tue Dec 03, 2019 10:44 am
Forum: Identifying Acidic & Basic Salts
Topic: HW 6D11
Replies: 7
Views: 88

Re: HW 6D11

To add onto Benjamin's post: https://slideplayer.com/slide/6819688/23/images/9/Acidity+of+Aqueous+Transition+Metal+Ions.jpg For problem e, the Aluminum cation will form those 6 bonds to water forming a coordination compound. Metal cations will act as acids because the strong positive charge of the m...
by Sebastian Lee 1L
Tue Dec 03, 2019 10:31 am
Forum: Calculating the pH of Salt Solutions
Topic: Sig Figs for logarithmic funcitons
Replies: 6
Views: 57

Re: Sig Figs for logarithmic funcitons

Actually, the sig figs for pH are a little different than normal. Essentially, if you are calculating the pH from a given concentration, the number of sig figs in the concentration is the number of sig figs you put AFTER the decimal point in the pH. For example, if I was given a 3.14 * 10 -2 M solut...
by Sebastian Lee 1L
Tue Dec 03, 2019 10:24 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Value of Kw?
Replies: 4
Views: 30

Re: Value of Kw?

For the calculations we will be doing in 14A, this is the value for K w . All this means is that in water at standard temperature and pressure, the concentration of hydronium ions [H 3 O + ] times the concentration of hydroxide ions [OH - ] is 1 x 10 -14 . This tells us that pH + pOH is 14. However,...
by Sebastian Lee 1L
Tue Dec 03, 2019 10:15 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Confusion about Ph>Pka
Replies: 2
Views: 24

Re: Confusion about Ph>Pka

What Dr. Lavelle was talking about was how much an acid will dissociate depending on the acidity of the solution it is in. Remember that for Bronsted acids, the acid in solution can dissociate into hydronium ions (H 3 O + ) and the conjugate base (A - ). For example, HF \rightleftharpoons H^{+} + F^...
by Sebastian Lee 1L
Sat Nov 30, 2019 1:39 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Textbook question 6B.3
Replies: 1
Views: 22

Re: Textbook question 6B.3

From my understanding, the second solution in part b is diluted relative to the desired solution. Therefore, to find the pH of the diluted acid, you need to find the new concentration/molarity. Using the equation M_{1}V_{1} = M_{2}V_{2} where M1 is .250, V1 is .2000, and V2 is .2500, you can find th...
by Sebastian Lee 1L
Tue Nov 26, 2019 3:59 pm
Forum: Naming
Topic: Polydentate
Replies: 4
Views: 33

Re: Polydentate

In coordination compounds, a polydentate ligand is a single molecule that can bind to the same central transition metal at multiple sites. This means that it likely will have multiple atoms with lone pairs that can create coordinate covalent bonds with the metal. For this type of question, it's help...
by Sebastian Lee 1L
Tue Nov 26, 2019 3:50 pm
Forum: Bronsted Acids & Bases
Topic: Forming a neutralization reaction
Replies: 2
Views: 33

Re: Forming a neutralization reaction

Seeing that there are assigned homework problems that are similar to that, I would be prepared to answer those if they do appear on the final.
by Sebastian Lee 1L
Tue Nov 26, 2019 3:49 pm
Forum: Naming
Topic: Final Exam
Replies: 3
Views: 38

Re: Final Exam

For the final, you should know the ligand names listed in the document Dr. Lavelle has provided: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/NamingCoordinationCompounds.pdf I believe the names in the textbook are the new IUPAC ones, but we only need to know how to name coordina...
by Sebastian Lee 1L
Mon Nov 25, 2019 3:46 pm
Forum: Naming
Topic: Roman numerals
Replies: 4
Views: 40

Re: Roman numerals

The roman numeral indicates the positive charge of the transition metal cation. This notation is often used since transition metals can take on multiple oxidation states. For example, to distinguish Fe 2+ and Fe 3+ you would write Iron (II) or Iron (III). If we have the coordination compound [Co (N...
by Sebastian Lee 1L
Mon Nov 25, 2019 3:35 pm
Forum: Amphoteric Compounds
Topic: amphoteric compounds
Replies: 2
Views: 43

Re: amphoteric compounds

We know that nonmetal oxides will typically form acidic compounds (ie. H 2 SO 4 or HNO 3 ) and that most metals oxides will form basic compounds (ie. CaO or NaO 2 ). However, amphoteric compounds are ones that can have either acid or base character depending on the reaction. Typically, elements near...
by Sebastian Lee 1L
Mon Nov 25, 2019 3:19 pm
Forum: Naming
Topic: Roman numerals
Replies: 4
Views: 40

Re: Roman numerals

The roman numeral indicates the positive charge of the transition metal cation. This notation is often used since transition metals can take on multiple oxidation states. For example, to distinguish Fe 2+ and Fe 3+ you would write Iron (II) or Iron (III). If we have the coordination compound [Co (NH...
by Sebastian Lee 1L
Mon Nov 25, 2019 3:12 pm
Forum: Bronsted Acids & Bases
Topic: Arrhenius, Bronsted, and Lewis
Replies: 1
Views: 18

Re: Arrhenius, Bronsted, and Lewis

The definition of an Arrhenius acid is a molecule that forms a hydronium ion (H 3 O + ) in the presence of water. An Arrhenius base forms a hydroxide ion (OH - ) in water. This definition applies to most Bronsted acids/bases. A Bronsted acid is a molecule that is a proton donor, meaning that it will...
by Sebastian Lee 1L
Tue Nov 19, 2019 10:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Instantaneous Dipole Moment
Replies: 4
Views: 27

Re: Instantaneous Dipole Moment

I believe this is referring to the fact that at any moment in time, electron distribution in a molecule can be slightly unequal. Electrons may be "hanging out" on one side of a molecule at an instant point in time. This creates a temporary/instantaneous dipole moment because of this unequa...
by Sebastian Lee 1L
Tue Nov 19, 2019 10:45 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: SO2 bond sigma and pi bond
Replies: 4
Views: 38

Re: SO2 bond sigma and pi bond

Also, extra stuff not regarding the original question: The VSEPR shape of SO 2 would be bent with a bond angle of slightly less than 120 degrees. This is because there are 3 regions of electron density (trigonal planar derived) but one of them is a lone pair which repels a little more than a bonded ...
by Sebastian Lee 1L
Tue Nov 19, 2019 10:40 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: SO2 bond sigma and pi bond
Replies: 4
Views: 38

Re: SO2 bond sigma and pi bond

The Lewis Structure for SO2 is a central Sulfur double bonded to each of the Oxygen atoms. A double bond consists of one sigma bond and one pi bond so in total you would have two sigma bonds and two pi bonds (one sigma and pi for one bonded Oxygen and another sigma and pi for the other).
by Sebastian Lee 1L
Tue Nov 19, 2019 10:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Cis vs Trans
Replies: 1
Views: 26

Re: Cis vs Trans

I suppose you should know that since there is likely a double bond in the cis and trans isomers, there is a pi bond between p orbitals which prevents the atoms from rotating. This ensures that the cis can't turn into a trans without some kind of chemical reaction.
by Sebastian Lee 1L
Tue Nov 19, 2019 10:32 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: diple induced dipole vs dipole-dipole
Replies: 1
Views: 20

Re: diple induced dipole vs dipole-dipole

Dipole-dipole interaction occurs when you have two polar molecules, each with a permanent dipole moment. The negative partial charge of one dipole is attracted to the positive partial charge of the other. For example, if I had H 2 O and NH 3 , the partial positive of the hydrogen would be attracted ...
by Sebastian Lee 1L
Tue Nov 19, 2019 10:26 pm
Forum: Bond Lengths & Energies
Topic: Interaction Potential Energy and Radius
Replies: 2
Views: 31

Re: Interaction Potential Energy and Radius

When atomic size increases, polarizability ( \alpha ) increases because the electrons are held on less tightly by the nucleus. High polarizability creates the stronger intermolecular forces described by the larger interaction potential energy. The distance between molecules is important but I think ...
by Sebastian Lee 1L
Tue Nov 19, 2019 3:05 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: 2
Views: 24

Hydrogen Bonding

I know that hydrogen bonding can occur when a hydrogen that is polar covalently bonded to a N,O, or F has a highly positive partial charge that it is attracted to a lone pair of a different molecule's electronegative atom. Can this other electronegative atom with the lone pair be any atom or does it...
by Sebastian Lee 1L
Mon Nov 18, 2019 5:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Structures for test two
Replies: 1
Views: 20

Re: Structures for test two

Yes. These have appeared in readings and HW.
You should know linear, trigonal planar, bent (<120 degrees), tetrahedral, trigonal pyramidal, bent (<109.5 degrees), trigonal bipyramidal, seesaw, T-shaped, linear (but with 3 lone pairs), octahedral, square pyramidal, and square planar.
by Sebastian Lee 1L
Mon Nov 18, 2019 5:06 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar/Nonpolar
Replies: 1
Views: 15

Re: Polar/Nonpolar

You have to understand the VSEPR shape of the molecule to determine its polarity. AsF 5 has a trigonal bipyramidal shape since it has 5 regions of electron density and no lone pairs. In a trigonal bipyramidal shape, you have 2 axial bonded atoms and 3 equatorial bonded atoms (2 are straight up and d...
by Sebastian Lee 1L
Mon Nov 18, 2019 5:01 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: Strength of IMF
Replies: 1
Views: 22

Re: Strength of IMF

I believe that the hydrogen bond (-20 kJ/mol) is indeed stronger than the ion-dipole force (-15 kJ/mol).
by Sebastian Lee 1L
Mon Nov 18, 2019 4:58 pm
Forum: Ionic & Covalent Bonds
Topic: Radicals and Bonds
Replies: 1
Views: 36

Re: Radicals and Bonds

I believe you would still treat the lone electron as one region of electron density. So it would act similar to a lone pair but have a lower repulsion than a lone pair would.
by Sebastian Lee 1L
Mon Nov 18, 2019 4:54 pm
Forum: Lewis Structures
Topic: HW #2.27
Replies: 1
Views: 35

Re: HW #2.27

The HCH bond in CH 2 2- has the smallest bond angle because it has a bent molecular shape. You are right in saying that the molecule will be based off a tetrahedral shape since it has 4 regions of electron density (2 bonding pairs and 2 lone pairs). Since it has 2 lone pairs, you would replace 2 ato...
by Sebastian Lee 1L
Fri Nov 15, 2019 3:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.5
Replies: 3
Views: 21

Re: 2E.5

Also to address your comment on H 2 O: H20 is based off the tetrahedral shape since it has 2 bonding pairs and 2 lone pairs (4 total regions of electron density). In a tetrahedral molecule, the angles are 109.5 degrees. When you replace two atoms for two lone pairs, this angle will be similar but ac...
by Sebastian Lee 1L
Fri Nov 15, 2019 3:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.5
Replies: 3
Views: 21

Re: 2E.5

Ok, so like you figure out, ClO 2 - has a lewis structure where a central chlorine is double bonded to oxygen atoms with a lone pair on the chlorine. Here we have 3 regions of electron density (2 bonding regions and one lone pair). A molecule with 3 regions of electron density will be based off the ...
by Sebastian Lee 1L
Fri Nov 15, 2019 3:05 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: polar/nonpolar
Replies: 2
Views: 13

Re: polar/nonpolar

Nonpolar molecules can have induced dipole-induced dipole (aka London dispersion) forces as well as dipole-induced dipole forces if in the presence of polar molecules. London forces arise when a temporary uneven distribution of electrons in any molecule give rise to a temporary partial charge which ...
by Sebastian Lee 1L
Fri Nov 15, 2019 2:53 pm
Forum: Bond Lengths & Energies
Topic: Bond lengths and lone pairs
Replies: 3
Views: 33

Re: Bond lengths and lone pairs

I think so. I believe that if an atom has more lone pairs it will have a longer and weaker bond with surrounding molecules that also have lone pairs. Since electrons repel each other, the lone pairs would want to be as far away as possible from other lone pairs on bonded atoms. In class, Dr. Lavelle...
by Sebastian Lee 1L
Fri Nov 15, 2019 2:48 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 Part c
Replies: 2
Views: 49

Re: 3F.5 Part c

Thank you! I talked to Dr. Lavelle and he mentioned that, like you said, the dipole moments mostly cancel out (not fully) which contributes to a relatively low polarity molecule. He also said that even though Flourine is highly electronegative, it is also pretty close to the Carbon since its atomic ...
by Sebastian Lee 1L
Fri Nov 15, 2019 2:45 pm
Forum: Administrative Questions and Class Announcements
Topic: Extra Credit?
Replies: 6
Views: 80

Re: Extra Credit?

Eileen Si 3H wrote:Test 2 should cover topics ranging from Lewis structures, intermolecular forces, and the VSEPR Model. Hopefully I'm not missing anything!


In lecture today, Dr. Lavelle also said that sigma and pi bonds will also be on the test. He will cover them first thing in Monday's lecture.
by Sebastian Lee 1L
Mon Nov 11, 2019 1:45 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 Part c
Replies: 2
Views: 49

3F.5 Part c

In Problem 3F.5 part c, it says that CHI 3 has stronger intermolecular forces than CHF 3 and will have a higher melting point. This difference is attributed to the difference in strength of induced dipole-induced dipole forces between the two molecules. I understand why CHI 3 has stronger London for...
by Sebastian Lee 1L
Tue Nov 05, 2019 10:38 pm
Forum: Photoelectric Effect
Topic: Light acts as a wave
Replies: 4
Views: 52

Re: Light acts as a wave

I'm pretty sure the photoelectric effect supports the particle/photon model of electromagnetic radiation because increasing the intensity of a low frequency light didn't eject electrons. It supports the theory of discrete, quantized packets of energy which each have energy dependent on frequency. In...
by Sebastian Lee 1L
Tue Nov 05, 2019 10:32 pm
Forum: Ionic & Covalent Bonds
Topic: Lattice Energy
Replies: 2
Views: 23

Re: Lattice Energy

by Sebastian Lee 1L
Tue Nov 05, 2019 10:30 pm
Forum: Lewis Structures
Topic: Exceptions to the Octet Rule Question
Replies: 5
Views: 31

Re: Exceptions to the Octet Rule Question

YES. Basically, any element in the 3rd row/period of the periodic table and beyond can have an expanded octet because they have access to the d orbital. For example, Xe (a noble gas) can make bonds and break the octet rule because it has free electron real estate in the 5d orbital.
by Sebastian Lee 1L
Tue Nov 05, 2019 10:27 pm
Forum: Quantum Numbers and The H-Atom
Topic: Clarification about Unique Quantum Numbers
Replies: 1
Views: 31

Re: Clarification about Unique Quantum Numbers

I believe so. Each orbital, of course, will have 2 electrons with different spin too (different quantum numbers).
by Sebastian Lee 1L
Tue Nov 05, 2019 10:25 pm
Forum: Octet Exceptions
Topic: Easy way to remember octet exceptions
Replies: 4
Views: 35

Re: Easy way to remember octet exceptions

Basically, if the element is in the 3rd row of the periodic table or beyond, it can have an expanded octet. For incomplete octets, it's H, He, Li, Be, B and the rest of the group 13 elements (like Al).
by Sebastian Lee 1L
Tue Nov 05, 2019 10:22 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Numbers Question
Replies: 2
Views: 29

Re: Quantum Numbers Question

If n=2: l can be l=0, 1 because l=0,...,n-1 If l=0: m l = 0 because m l = -l,...,l If l=1: m l = -1, 0, 1 So we can see how many m l numbers there are which correspond to each orbital. There is one 2s orbital (n=2, l=0) and there are three 2p orbitals (n=2, l=1) each one having a m l of -1, 0, or 1....
by Sebastian Lee 1L
Tue Nov 05, 2019 10:15 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Numbers Question
Replies: 3
Views: 46

Re: Quantum Numbers Question

Okay so if n=4: l=0, 1, 2, 3 For l=0: m l = 0 For l=1: m l = -1, 0, 1 For l=2: m l = -2, -1, 0, 1, 2 For l=3: m l = -3, -2, -1, 0, 1, 2, 3 For each orbital there can be two electrons (one with spin up (m s = +1/2) and one with spin down (m s = -1/2)). If we add up all the orbitals, there are 16. Sin...
by Sebastian Lee 1L
Tue Nov 05, 2019 10:09 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: polarizability/polarizing power and periodicity
Replies: 2
Views: 16

Re: polarizability/polarizing power and periodicity

I believe all these concepts are related. An anion will be more polarizable if it has a larger ionic radius and thus has a lower ionization energy/lower electron affinity. The effective nuclear charge is lower so the electrons are held less tightly and the electron cloud is more easily distorted to ...
by Sebastian Lee 1L
Tue Nov 05, 2019 10:02 pm
Forum: Electronegativity
Topic: Electronegativity Chart
Replies: 5
Views: 43

Re: Electronegativity Chart

I think you should definitely know the general trend that electronegativity increases as you go to the right across a period and up a group. This way you can roughly determine what kind of dipole moment may appear in a molecule. The only time I think we would need to have an electronegativity chart ...
by Sebastian Lee 1L
Tue Nov 05, 2019 9:57 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Determining which bonds are more polar
Replies: 4
Views: 36

Re: Determining which bonds are more polar

Mg-O is more polar than B-O because the electronegativity difference between Mg and O is higher than between B and O. I think you're mistaken in saying that Mg is a smaller radius than B, because I'm pretty sure that atomic radius increases as you go down and to the left of the periodic table. Mg ha...
by Sebastian Lee 1L
Sat Nov 02, 2019 11:24 pm
Forum: Octet Exceptions
Topic: Boron and Aluminum
Replies: 1
Views: 20

Re: Boron and Aluminum

From my understanding, since both Boron and Aluminum are in the 13th group on the periodic table, they only have 3 valence electrons. Since they have a relatively low electron affinity, they won't feasibly gain a complete octet through covalent bonding. However, they can be stable with 5 valence ele...
by Sebastian Lee 1L
Sat Nov 02, 2019 11:14 pm
Forum: Dipole Moments
Topic: Midterm
Replies: 8
Views: 90

Re: Midterm

YES. You will have to know about dipole moments caused by electronegativity in covalent bonds. What you won't need to know is the specific intermolecular forces like dipole-dipole or dipole-induced dipoole BUT you should understand why many molecules will have partial charges and a dipole moment.
by Sebastian Lee 1L
Sat Nov 02, 2019 11:11 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Midterm Q
Replies: 2
Views: 25

Re: Atomic Spectra Midterm Q

I don't think you'll need to memorize each specific color. Just know that visible light is from about 400-700nm and that ~400 is violet while ~700 is red light.
by Sebastian Lee 1L
Thu Oct 31, 2019 3:00 pm
Forum: Lewis Structures
Topic: HW Problem 2C.5
Replies: 1
Views: 31

Re: HW Problem 2C.5

A radical is a molecule in which one of the atoms has a single lone electron. If you draw the Lewis Dot Structure for a radical, you would be left with one dot or electron by itself, unpaired with any other electrons. So if you have drawn the correct structure with bonds and lone pairs but you have ...
by Sebastian Lee 1L
Thu Oct 31, 2019 11:11 am
Forum: Resonance Structures
Topic: C4H4
Replies: 2
Views: 19

Re: C4H4

If you arrange the carbon atoms in a line, I don't think they will have enough bonds to make an octet. With C 4 H 4 , each C atom is single bonded to one H, single bonded to another C, and double bonded to a different C. This gives each Carbon 4 bonds if put in a square configuration, satisfying the...
by Sebastian Lee 1L
Thu Oct 31, 2019 11:06 am
Forum: Electronegativity
Topic: Electronegativity vs Electron Affinity of Nitrogen
Replies: 3
Views: 17

Electronegativity vs Electron Affinity of Nitrogen

I noticed that Nitrogen has a quite high electronegativity value of 3.04 but has a very low electron affinity of almost 0. I understand that Nitrogen has such a low electron affinity because adding an electron to its stable half-full 2p subshell is actually energetically unfavorable. But why does Ni...
by Sebastian Lee 1L
Mon Oct 28, 2019 10:10 am
Forum: Octet Exceptions
Topic: Sharing more than 8 e-
Replies: 1
Views: 18

Re: Sharing more than 8 e-

Certain elements can have expanded valence shells, more than 8 electrons in their valence shell. I believe this can only happen with nonmetals in the 3rd row of the periodic table and down. This is because they can put electrons into the d subshell, even though the ground state atom doesn't have ele...
by Sebastian Lee 1L
Mon Oct 28, 2019 10:03 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 11
Views: 97

Re: Midterm

Check out this: https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

Yes, the midterm will be on Wednesday from 6-8pm. It will cover Fundamentals, Quantum World, and Chemical Bonds. The format will be 8 questions in 2 hours, free response like last test.
by Sebastian Lee 1L
Mon Oct 28, 2019 10:01 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 2
Views: 21

Re: Midterm

https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

8 questions in 2 hours. Probably multi-step free response.
by Sebastian Lee 1L
Mon Oct 28, 2019 10:00 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 5
Views: 65

Re: Midterm

https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

According to the info, it should cover Fundamentals, Quantum World, and Chemical Bonds.
by Sebastian Lee 1L
Mon Oct 28, 2019 9:57 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 2
Views: 38

Re: Midterm

https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

8 questions, likely free response like the first test
by Sebastian Lee 1L
Mon Oct 28, 2019 9:55 am
Forum: Administrative Questions and Class Announcements
Topic: Midterm Time
Replies: 1
Views: 17

Re: Midterm Time

https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

Wednesday from 6-8 pm so not during class.
by Sebastian Lee 1L
Sat Oct 26, 2019 11:44 pm
Forum: Lewis Structures
Topic: Drawing a Lewis Structure
Replies: 2
Views: 23

Re: Drawing a Lewis Structure

Fluorine only needs to make one bond in order to reach a stable octet of valence electrons. So each fluorine will make a single bond with the bromine atom to become stable. This does indeed result in Br having 10 electrons in its valence shell (6 from the bonds and 4 from the 2 lone pairs). (Bromine...
by Sebastian Lee 1L
Thu Oct 24, 2019 3:42 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2A.5: What happens with s and d orbitals?
Replies: 2
Views: 19

Re: 2A.5: What happens with s and d orbitals?

Great question! So the ground state of normal Tl is [Xe] 4f 14 5d 10 6s 2 6p 1 . To form a cation, the outermost valence electrons of the atom will be removed. The outermost electrons are going to be the ones in the 6s and 6p subshells. So if we have Tl 3+ , we remove the 3 electrons from the 6s and...
by Sebastian Lee 1L
Wed Oct 23, 2019 8:48 pm
Forum: Trends in The Periodic Table
Topic: Effective Nuclear Charge
Replies: 5
Views: 46

Re: Effective Nuclear Charge

I believe effective nuclear charge actually describes how much attraction an electron feels from the positive nucleus. Basically, a valence electron in a multi-electron atom will have a lower effective nuclear charge (Z eff e) than an electron closer to the atom. This is because of the shielding eff...
by Sebastian Lee 1L
Wed Oct 23, 2019 8:40 pm
Forum: Lewis Structures
Topic: Valence e in d block
Replies: 5
Views: 34

Re: Valence e in d block

Yes I believe most d-block elements will only have the s-shell valence electrons of the energy level above the d. This is helpful to know when considering making cations from these metals. The electrons will be removed from the outermost shell which consists only of its highest energy s-shell electr...
by Sebastian Lee 1L
Wed Oct 23, 2019 8:31 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: General Terminology for Electron Configuration
Replies: 2
Views: 15

Re: General Terminology for Electron Configuration

The shell is described by the primary quantum number n. A shell refers to the general energy level and distance from the nucleus. The n=1 shell is the lowest energy level. The subshell is described by the angular orbital momentum quantum number l. A subshell refers to the general shape. If l=0, it's...
by Sebastian Lee 1L
Wed Oct 23, 2019 8:19 pm
Forum: Ionic & Covalent Bonds
Topic: Focus 2.B problem B9
Replies: 2
Views: 26

Re: Focus 2.B problem B9

Also, we know it'll have to be an ionic compound because it's between a metal that has a very low ionization energy and a nonmetal with a high ionization energy/high electron affinity.
by Sebastian Lee 1L
Wed Oct 23, 2019 8:17 pm
Forum: Ionic & Covalent Bonds
Topic: Focus 2.B problem B9
Replies: 2
Views: 26

Re: Focus 2.B problem B9

Because phosphorous is a non-metal in the p-block, we know it will form an anion in an ionic bond. P has 5 valence electrons (2s 2 2p 3 ). In order to reach the desired 8 valence electrons to become stable (octet rule), it must gain 3 electrons and become P 3- . Potassium is an alkali metal so it wi...
by Sebastian Lee 1L
Sat Oct 19, 2019 9:51 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration
Replies: 1
Views: 17

Re: Electron Configuration

Basically, when writing electron configurations you must write in order of lowest energy to highest energy. In K and Ca, the 4s subshell is of a slightly lower energy than the 3d subshell so electrons occupy that space first. However, when Z>20 (you enter the d-block), the 3d subshell actually shift...
by Sebastian Lee 1L
Sat Oct 19, 2019 9:47 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Which Element to Use in Electron Configurations
Replies: 5
Views: 33

Re: Which Element to Use in Electron Configurations

Typically you would use the last element with a full shell (typically a noble gas) to shorthand. The problem with using the last element is that it would be confusing when identifying the extra electron in your element. For example, if I was doing the configuration for Ca, it would be weird to say [...
by Sebastian Lee 1L
Sat Oct 19, 2019 9:41 pm
Forum: Properties of Light
Topic: 1A. 15
Replies: 3
Views: 33

Re: 1A. 15

Okay so we know that the energy of the light emitted is caused by the transition of the electron from one energy level to another. We can represent this as \Delta E = E_{final} - E_{initial} . We also know that, for hydrogen, the energy of a specific energy level is given by the equation E = -\frac{...
by Sebastian Lee 1L
Sat Oct 19, 2019 9:20 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Spin
Replies: 4
Views: 46

Re: Magnetic Spin

I think you should understand electron spin as it pertains to electron configurations of certain elements. For instance, the Pauli Exclusion Principle states that if 2 electrons are in the same orbital, they should have opposite spins (spin up and spin down). Hund's rule says that electrons in the s...
by Sebastian Lee 1L
Sat Oct 19, 2019 9:15 pm
Forum: Quantum Numbers and The H-Atom
Topic: Values of l
Replies: 2
Views: 42

Re: Values of l

I believe you are referring to the possible values of the magnetic quantum number, m l . m l can take on the values from -l to l as you were saying. Each of these corresponds to the specific orientation of the orbital on the axes. For example, if l=2, m l can be -2, -1, 0, 1, or 2. Each of these 5 n...
by Sebastian Lee 1L
Sat Oct 19, 2019 9:11 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shell, Subshell, Orbital Terminology
Replies: 8
Views: 89

Re: Shell, Subshell, Orbital Terminology

Yes, I believe that is correct! I also used to think that the subshells were "orbitals".
by Sebastian Lee 1L
Sat Oct 19, 2019 9:07 pm
Forum: Quantum Numbers and The H-Atom
Topic: Ml values
Replies: 2
Views: 31

Re: Ml values

M l is the magnetic quantum number for an electron orbital/state. It can take the values of numbers from -l to +l so if l=2 (d-subshell), m l can be -2, -1, 0, 1, or 2. These values relate to the orientation of the orbital around the nucleus, meaning what axes/planes it lies on. For example, for the...
by Sebastian Lee 1L
Tue Oct 15, 2019 11:47 am
Forum: *Shrodinger Equation
Topic: Schrodinger's Equation
Replies: 8
Views: 69

Re: Schrodinger's Equation

Is the Schrodinger equation typically used to find the wavefunction itself or the total energy (kinetic + potential) of the wavefunction? Do observations reveal the total energy and allow the wavefunction to be derived from it?
by Sebastian Lee 1L
Tue Oct 15, 2019 11:34 am
Forum: DeBroglie Equation
Topic: HW Question 1.B.15
Replies: 3
Views: 22

Re: HW Question 1.B.15

The mass of the electron is a constant that should be given on the constants and equations sheet. The mass of an electron is 9.109 x 10-31 kg. Using the deBroglie equation you can find the wavelength with Planck's constant, velocity, and mass.
by Sebastian Lee 1L
Sat Oct 12, 2019 10:31 am
Forum: Properties of Electrons
Topic: De Broglie Problems
Replies: 4
Views: 35

Re: De Broglie Problems

I believe Dr. Lavelle said during lecture that any object with less than 10^-15 m wavelength would be undetectable--it wouldn't show wave-like properties, just particle properties. For example, an electron with a very small mass should have a detectable wavelength, even if it's velocity is high. How...
by Sebastian Lee 1L
Wed Oct 09, 2019 10:03 pm
Forum: Properties of Light
Topic: Problem 1A.15 and the Rydberg formula
Replies: 3
Views: 41

Problem 1A.15 w/o Rydberg formula

Ok, after lecture today I understand that to find the energy levels we can use \lambda =\frac{c}{\nu } , \Delta E = h\nu , \Delta E = E(final)-E(initial) , and En=-\frac{hR}{n^2} to solve the problem. Using the wavelength to get frequency and then frequency to get change in energy, w...
by Sebastian Lee 1L
Tue Oct 08, 2019 11:03 pm
Forum: Properties of Light
Topic: Light intensity
Replies: 10
Views: 74

Re: Light intensity

The energy per photon is equal to Planck's constant times frequency of each photon. The threshold energy (or work function) is how much energy is required per photon to eject an electron from the metal. If the energy per photon equals the threshold energy, then an electron will be ejected from the m...
by Sebastian Lee 1L
Tue Oct 08, 2019 10:58 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: The relationship of precision between position and momentum
Replies: 3
Views: 36

Re: The relationship of precision between position and momentum

The Heisenberg uncertainty principle shows the complementarity of location and momentum. If one property is known to a precise extent, the other can't be known as well simultaneously. We know from the de Broglie equation that \lambda = \frac{h}{p} . If we know the precise momentum, we assume wave-li...
by Sebastian Lee 1L
Tue Oct 08, 2019 10:39 pm
Forum: SI Units, Unit Conversions
Topic: Will we have to know how to convert from Fahrenheit, Celsius, and Kelvin?
Replies: 4
Views: 73

Re: Will we have to know how to convert from Fahrenheit, Celsius, and Kelvin?

I doubt you would need to memorize the fahrenheit-celsius formulas as fahrenheit is rarely used in chemistry. However, I would suggest that you remember that Kelvin is Celsius + 273.15 (though I believe this is provided on the constants and equations sheet). This will probably be more relevant when ...
by Sebastian Lee 1L
Fri Oct 04, 2019 3:58 pm
Forum: Properties of Light
Topic: Problem 1A.15 and the Rydberg formula
Replies: 3
Views: 41

Problem 1A.15 and the Rydberg formula

1A.15: In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.66 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line. So I found the frequency of the emission to be 2.92 * 10 15 Hz usi...
by Sebastian Lee 1L
Thu Oct 03, 2019 8:40 pm
Forum: Molarity, Solutions, Dilutions
Topic: Homework Problem G17 Part B
Replies: 2
Views: 28

Re: Homework Problem G17 Part B

Yeah, the only difference is that in part a, you have anhydrous copper(ii) sulfate whereas in part b, you have copper(ii) sulfate pentahydrate. The 5H2O on the end means that there are water molecules in the crystalline structure of CuSO4 but are not totally bonded to the molecule. The only differen...
by Sebastian Lee 1L
Thu Oct 03, 2019 8:34 pm
Forum: Significant Figures
Topic: All students read this sig fig post [ENDORSED]
Replies: 116
Views: 11170

Re: All students read this sig fig post [ENDORSED]

melinak1 wrote:is there a consistent rule of how many sig figs there should be? or does it depends on what the problem is asking for?

The number of sig figs you need in your answer depends on how many sig figs are give in the numbers of the problem.
by Sebastian Lee 1L
Thu Oct 03, 2019 5:48 pm
Forum: Molarity, Solutions, Dilutions
Topic: Clarification for G17b ?
Replies: 4
Views: 29

Re: Clarification for G17b ?

To answer Ashley's question: The dot in CuSo4 • 5H2O signifies that the water (known as the water of hydration/crystallization) is bound to the copper(ii) sulfate in its crystalline framework. The water molecules can be evaporated away, leaving just the anhydrous salt. Note that the water can only b...
by Sebastian Lee 1L
Thu Oct 03, 2019 4:49 pm
Forum: Limiting Reactant Calculations
Topic: Homework Week 1
Replies: 18
Views: 187

Re: Homework Week 1

To satisfy the requirements, you only need to answer ANY 5 questions from the problem list and turn them in during tomorrow's lecture. HOWEVER, if you have the time and/or want extra practice, I would strongly suggest that you do more than the required 5 problems. Professor Lavelle states that he in...
by Sebastian Lee 1L
Wed Oct 02, 2019 11:54 pm
Forum: SI Units, Unit Conversions
Topic: Fundamentals Practice Problem E3
Replies: 3
Views: 70

Re: Fundamentals Practice Problem E3

You're absolutely correct! The gallium atoms have a third of the molar mass of the astatine atoms so you would need 3 times as many gallium atoms to balance out the astatine atoms. Conversely, the amount of astatine would be 1/3 the amount of gallium, so 9 atoms of gallium requires 3 atoms of astati...

Go to advanced search