## Search found 112 matches

Sat Jan 23, 2021 10:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Material Accessible during Exams
Replies: 6
Views: 18

### Material Accessible during Exams

For several questions in the textbook, they ask questions and do not provide the Ka/Kb, and I assume they want us to reference the table. Would we have access to a table of Ka/Kb values for our exams or would they be provided in the question? Would any need to be memorized?
Thu Jan 21, 2021 9:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook 6E #1
Replies: 2
Views: 13

### Re: Textbook 6E #1

Hi yes you are right, for polyprotic acids we will need to do the process multiple times. Even though the Ka is much smaller for the second and even third protonation, it will still have an effect on the pH. It will most likely be specified in that the problem will give you the Ka1, Ka2, etc., thus ...
Thu Jan 21, 2021 9:15 pm
Forum: Phase Changes & Related Calculations
Topic: How would a phase change diagram look like for the process of sublimation?
Replies: 3
Views: 11

### How would a phase change diagram look like for the process of sublimation?

In Wednesday's lecture, we looked at a phase change diagram of water, where it transitioned from solid to vapor with flat lines at the phase changes. How would the diagram look for sublimation, such as the vaporization of dry ice? Would it just jump directly from solid to gas? Thank you!
Wed Jan 20, 2021 6:01 pm
Forum: Phase Changes & Related Calculations
Topic: Question about Steam Causing Severe Burns
Replies: 3
Views: 28

### Re: Question about Steam Causing Severe Burns

Yes you are correct! Since the skin is much colder than the steam, the heat immediately transfers to the skin and hydrogen bonds are actually being formed, not broken (since energy is released and making bonds releases energy because its favorable).
Wed Jan 20, 2021 11:58 am
Forum: Phase Changes & Related Calculations
Topic: Adding Heat but Temp remains constant
Replies: 11
Views: 51

### Adding Heat but Temp remains constant

So in lecture today, Dr. Lavelle said that the temperature remains constant during a phase change, even though heat is being supplied. If the heat is being used to break the bonds, where is going after that process is complete? I'm confused by how this follows the Law of Conservation of Energy.
Wed Jan 20, 2021 9:23 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Help on 5.33 in the Textbook
Replies: 4
Views: 33

### Help on 5.33 in the Textbook

5.33 Dissociation of a diatomic molecule, X2(g)⇌2 X(g) occurs at 500 K. The equilibrium state of the reaction is shown in 1 and the equilibrium state in the same container after a change has occurred is shown in 2. Which of the following changes will produce the composition shown? (a) Increasing the...
Fri Jan 15, 2021 11:46 am
Forum: Administrative Questions and Class Announcements
Topic: Are we covering Buffers?
Replies: 1
Views: 19

### Are we covering Buffers?

In this class are we going to be covering buffers? It wasn't in today's lecture but it seems like a pretty important topic in acids and bases.
Fri Jan 15, 2021 11:30 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Factoring in the Hydronium Concentration already present in water from today's Lecture
Replies: 1
Views: 26

### Factoring in the Hydronium Concentration already present in water from today's Lecture

In today's lecture, Dr. Lavelle mentioned how we ignore the hydronium already present in water because of how small it is compared to the amount from the acid. Wouldn't that 10^-7 moles of hydronium not matter anyway because the 10^-7 moles of hydroxide also present in the water takes away 10^-7 mol...
Thu Jan 14, 2021 2:39 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Gas
Replies: 16
Views: 73

### Re: Gas

The question should always specify the units, since the gas constant we use is dependent on the units of the problem. Furthermore, it would only matter when choosing the gas constant because bar and atm are essentially equivalent.
Thu Jan 14, 2021 2:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pKa and pH
Replies: 10
Views: 45

### Re: pKa and pH

pKa and pH are not the same, because pKa is standardized for each acid while pH is measured at any time and can vary. Check out this website for some more insight. https://www.differencebetween.com/diffe ... nd-vs-pka/
Wed Jan 13, 2021 2:27 pm
Forum: Student Social/Study Group
Topic: Study Habits
Replies: 96
Views: 264

### Re: Study Habits

Hi, the best tips I can give you are to develop a study plan, minimize distractions, and try to avoid procrastinating or cramming.
Wed Jan 13, 2021 2:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework problem 7
Replies: 4
Views: 33

### Re: Homework problem 7

I agree with the above answer, but also if a reaction is endothermic you can think of heat as a reactant, so increasing temperature a.k.a adding heat, will act like adding a reactant. The denominator will be larger and Q will be less than K, and the reactant shifts towards the products.
Wed Jan 13, 2021 1:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: [H30+]=[OH-] ???
Replies: 8
Views: 45

### Re: [H30+]=[OH-] ???

Yes that is correct, you would square root the value. This makes sense because water should have a neutral pH of 7, which would happen as a result of hydroxide and hydronium concentrations being equal.
Wed Jan 13, 2021 11:45 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Textbook question 6B 11
Replies: 2
Views: 24

### Re: Textbook question 6B 11

I agree with the above answer, but just keep in mind that when you add a metallic oxide to water it makes a base. Adding solid Na2O to water would create sodium hydroxide, which was the cause of the pH lowering.
Wed Jan 06, 2021 11:59 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Would equilibrium favor resonance?
Replies: 3
Views: 16

### Would equilibrium favor resonance?

If a reaction has a reactant or a product that is a resonance hybrid, would the reaction favor that side since the resonance hybrid would be more stable?
Tue Jan 05, 2021 6:43 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: temperature change in reactions
Replies: 11
Views: 84

### Re: temperature change in reactions

I agree with all of the previous replies, but if you were asking from more of a technical standpoint we will learn about that more in the Chemical Kinetics unit. When temperature is increased, the molecules move faster and have higher energy, therefore leading to the reaction progressing faster in t...
Tue Jan 05, 2021 6:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pure Substances Concentration
Replies: 4
Views: 21

### Re: Pure Substances Concentration

Aqueous substances are simply dissolved in water, they do not make up liquid as a pure substance. For example, hydrochloric acid is not often 100% HCl, it is normally a small percentage of the total volume, such as 5% HCl.
Tue Jan 05, 2021 6:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium 1A Question 19
Replies: 3
Views: 30

### Re: Chemical Equilibrium 1A Question 19

I'm pretty sure the answer is A, but if anyone else thinks otherwise let me know. It should just be the equilibrium concentrations of the products divided by the equilibrium concentrations of the reactants, all raised to the power of the stoichiometric coefficients.
Mon Jan 04, 2021 2:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs. Kc
Replies: 15
Views: 80

### Re: K vs. Kc

In my understanding, K and Kc are almost interchangeable, but K is more general, while Kc is mainly used in the context of comparing concentrations. K can be used to cover both the equilibrium constant of concentrations, Kc, and the equilibrium constant of gas pressures, Kp. Dr. Lavelle with probabl...
Mon Jan 04, 2021 2:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pure Liquids [ENDORSED]
Replies: 3
Views: 57

### Re: Pure Liquids[ENDORSED]

For example, if a compound is aqueous in 1L of water, the concentration of the water would be the moles of water divided by its volume. 1 Liter of water is 1000 grams of water, since 1 g is equal to 1 cubic centimeter. 1000 grams of water divided by 18.016 grams per mole, divided by 1 Liter, gives a...
Fri Dec 11, 2020 2:58 pm
Forum: Lewis Acids & Bases
Topic: Aluminum chloride example from Bruincast review today
Replies: 1
Views: 28

### Aluminum chloride example from Bruincast review today

In the aluminum chloride example from the lecture today, I know it is a Lewis Acid, but what would aluminum chloride be in the Bronsted definition? Does the Bronsted definition not apply to it?
Thu Dec 10, 2020 6:16 pm
Forum: Polyprotic Acids & Bases
Topic: Polyprotic Acids
Replies: 6
Views: 49

### Re: Polyprotic Acids

Yes, they are acids that are able to donate more than one hydrogen in solution. Some examples are sulfuric acid and phosphoric acid. Keep in mind the Ka decreases greatly after every proton loss due to increased attraction.
Thu Dec 10, 2020 6:13 pm
Forum: Naming
Topic: "ate" and "ic"
Replies: 4
Views: 42

### Re: "ate" and "ic"

Hi, I'm not sure where to use "ate", but "ic" is used to name an acid with an "ate" compound. For example, the acid of nitrate is nitric acid and the acid of chlorate is chloric acid.
Thu Dec 10, 2020 1:39 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty of Position in an Atom
Replies: 2
Views: 42

### Uncertainty of Position in an Atom

If the uncertainty in position of an electron confined to an atomic radius is given, would we use the atomic radius as the uncertainty or would we double it and use the diameter?
Thu Dec 10, 2020 1:37 pm
Forum: Properties of Light
Topic: What are the ranges of wavelength for each type of electromagnetic radiation?
Replies: 5
Views: 60

### What are the ranges of wavelength for each type of electromagnetic radiation?

Could someone please explain the ranges of wavelength for each type of electromagnetic radiation? The ranges are always so ambiguous to me and I have always had trouble identifying the type of light in the problem based on its wavelength.
Wed Dec 09, 2020 10:10 am
Forum: *Titrations & Titration Calculations
Topic: Stoichiometric Point: Mol acid = mol base
Replies: 1
Views: 43

### Stoichiometric Point: Mol acid = mol base

In lecture today, 12/9, Dr. Lavelle said at the stoichiometric point mol acid = mol base. Would it be more accurate to say that at the point mol hydronium equals mol hydroxide? Since some acids are polyprotic and some bases can release 2 moles of hydroxide, like Ca(OH)2. For Ca(OH)2, if the moles of...
Mon Dec 07, 2020 11:00 am
Forum: Identifying Acidic & Basic Salts
Topic: Metal Cation Example from Lecture 12/7
Replies: 2
Views: 35

### Metal Cation Example from Lecture 12/7

In the example from lecture about Fe3+ releasing H+ in solution by pulling away electron density and making the OH bond weaker, where is the OH- ion going after the H+ is removed? Is it bonding to the Fe3+ ion as a ligand?
Sun Dec 06, 2020 8:01 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Naming Coordination Compounds
Replies: 7
Views: 65

### Re: Naming Coordination Compounds

Most ligands and atoms on the left and right sides of the periodic table are given as either polyatomic ions, elements, or simple compounds which we probably already have memorized the charges of. The only difficult ones would be in the Ligand chart on Dr. Lavelle's website, such as the charge of Ox...
Sun Dec 06, 2020 7:39 am
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: List of Strong Bases and Weak Bases
Replies: 6
Views: 181

### Re: List of Strong Bases and Weak Bases

Andre Fabian 1G wrote:
Mg(OH)2 is not a strong base due to its limited solubility; given that this would decrease the amount of OH- ions dissociated in the solution, the molecule is therefore classified as a weak base.

Hope this helps!
Andre

It does, thank you Andre!
Sat Dec 05, 2020 11:04 am
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: List of Strong Bases and Weak Bases
Replies: 6
Views: 181

### Re: List of Strong Bases and Weak Bases

To add on to what Alice said, HClO3 can also be considered a strong acid, but not in every situation. For the strong bases, it's pretty much a "b" shape on the left side of the period table (LiOH, NaOH, KOH, RbOH, CsOH, CaOH, SrOH, BaOH) Why does Mg(OH)2 not fall into the strong base cate...
Fri Dec 04, 2020 3:51 pm
Forum: Bronsted Acids & Bases
Topic: HClO3 Strength for 14A
Replies: 3
Views: 41

### HClO3 Strength for 14A

In Chem 14A, is chloric acid, HClO3, a strong acid or would it classify as a weak acid? In high school we were told that it was weak, but the textbook says its strong.
Fri Dec 04, 2020 12:43 pm
Forum: Amphoteric Compounds
Topic: Amphoteric - how to tell if it is an acid or base
Replies: 4
Views: 67

### Re: Amphoteric - how to tell if it is an acid or base

In addition, it would be entirely dependent on what molecule the amphoteric molecule is interacting with. If it is interacting with an acidic substance, it would be a base, and vice versa for a basic substance.
Fri Dec 04, 2020 11:08 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HClO vs. HBrO vs. HIO example
Replies: 3
Views: 59

### HClO vs. HBrO vs. HIO example

In the example comparing the pH of HClO, HBrO, and HIO, why is the halogen the atom that receives the electrons and makes the anion more stable if Oxygen is more electronegative? Wouldn't oxygen have a stronger pull on the electrons than the halogens?
Wed Dec 02, 2020 6:39 am
Forum: Administrative Questions and Class Announcements
Topic: Textbook Issue
Replies: 5
Views: 97

### Re: Textbook Issue

I sometimes have this problem too with the math not "Typesetting", so I downloaded the Bookshelf app from the Microsoft Store. It's available offline and it loads like 10 times faster, it's really helpful!
Tue Dec 01, 2020 8:42 pm
Forum: Naming
Topic: Textbook problem 9c.3
Replies: 4
Views: 47

### Re: Textbook problem 9c.3

If the overall compound is neutral, there would need to be 3 potassiums to balance out the charge. Hexacyanide would be -6, chromium (III) would be 3+, so 3 potassiums would give the other +3 to make the net charge 0. If it didn't specify the overall charge, then I'm not sure how to approach the num...
Tue Dec 01, 2020 8:38 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: charge of oxalato
Replies: 4
Views: 57

### Re: charge of oxalato

I think Dr. Lavelle said to memorize the charges for each ligand because they will not be provided. You don't need to worry about the structure, that won't be covered in this class.
Sun Nov 29, 2020 1:17 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelate
Replies: 3
Views: 32

### Re: Chelate

You would also need to look at the overall structure of the molecule, if the ligands form a ring around the central atom and the ring includes the central atom, it would be a chelate, and the ligands that are part of it would be chelating ligands.
Sun Nov 29, 2020 1:14 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Table 9C1
Replies: 1
Views: 25

### Re: Table 9C1

Hi, in a UA Session the UA told me we would need to memorize the common ligands and their specific charges. For example, if a question asked about EDTA we would have to have memorized that it has a -4 charge. That would help us with oxidation numbers and determining how many bonds it can form with t...
Sun Nov 29, 2020 1:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Delocalized pi bond
Replies: 4
Views: 26

### Re: Delocalized pi bond

A delocalized pi bond is basically what you get when the pi bond is part of a resonance structure. It just means that the electrons of the bond are free to move between the two atoms. So, you'd have a delocalized pi bond when you have a molecule with resonance. I agree, in addition if you remember ...
Thu Nov 26, 2020 10:37 am
Forum: Administrative Questions and Class Announcements
Topic: Final exam (fall 2020 quarter)
Replies: 20
Views: 233

### Re: Final exam (fall 2020 quarter)

Will the final follow the same format as midterms or will everyone take it at the same time?
Thu Nov 26, 2020 10:35 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: S character
Replies: 1
Views: 38

### Re: S character

viewtopic.php?t=1255 Check out this post on Chemistry Community, I think it's helpful to explain what S-character means. Hope this helps!
Thu Nov 26, 2020 8:50 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: TM and coordination compounds
Replies: 2
Views: 51

### Re: TM and coordination compounds

I can answer the first question, coordination compounds do not need to have a transition metal. For example, take BF3, a well known lewis acid. Boron is not a transition metal but can make coordinate covalent bonds, such as with F-.
Thu Nov 26, 2020 8:47 am
Forum: Lewis Structures
Topic: HW 2E.13 (a)
Replies: 2
Views: 32

### Re: HW 2E.13 (a)

The two molecules would have the same overall formal charge, but three single bonds gives each terminal iodine a formal charge of zero and puts the negative formal charge on the central iodine. A double bond would make one of the terminal iodines have a +1 charge, and the central atom would have a -...
Wed Nov 25, 2020 10:40 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ni (NH3)2 Cl2 example from Lecture
Replies: 1
Views: 43

### Ni (NH3)2 Cl2 example from Lecture

How does Nickel 2+ have room for 6 bonds? I know expanded octets apply to atoms in and after the 3rd row, but I thought only p-block elements could use the empty d shells, not transition metals. The nickel 2+ electron configuration only has 2 unpaired electrons in the 3d shell and an empty 4s shell,...
Sun Nov 22, 2020 6:58 am
Forum: Student Social/Study Group
Topic: Study Tips for Final Exam
Replies: 57
Views: 415

### Re: Study Tips for Final Exam

I'm definitely going to review Dr.Lavelle's recommended textbook problems because they were super helpful for the midterms! I also plan on rereading the textbook and making condensed notes. I might rewatch Dr. Lavelle's lectures and the Organic Chemistry Tutor on youtube for the concepts I'm strugg...
Sat Nov 21, 2020 7:34 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pair repulsion
Replies: 4
Views: 33

### Re: lone pair repulsion

Also, bonding pairs are in between the nuclei of two atoms, so their negative charge is more confined to the bond region. The lone pair is only affected by one nucleus and can move around freely to repel other lone pairs and bonding pairs.
Fri Nov 20, 2020 11:41 am
Forum: Hybridization
Topic: what are terminal atoms?
Replies: 3
Views: 1518

### Re: what are terminal atoms?

I read from the textbook that terminal atoms are not regarded as hybridized. (i.e. the Cl molecules in PCl 5 ) What are the definition of terminal atoms? Thank you! Yeah, the central atom's valence shell has been hybridized in order to accommodate the electrons needed for a stable structure. The te...
Thu Nov 19, 2020 3:49 pm
Forum: Bond Lengths & Energies
Topic: Boiling/Melting Point
Replies: 20
Views: 145

### Re: Boiling/Melting Point

We would look at intermolecular forces because those are the forces that are overcome to initiate a phase change. For example, when H2O (liquid) is evaporated into H2O(gas) the Hydrogen bonds in the liquid have been overcome to separate the molecules. The O-H bonds in each H2O molecule have not been...
Thu Nov 19, 2020 3:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: n, l, mi
Replies: 8
Views: 57

### Re: n, l, mi

I think this post should be under the forum regarding quantum numbers, not under VSEPR Theory. Just warning you, because I think I remember Dr. Lavelle saying students don't earn points for posts in the wrong section and the post may be deleted.
Thu Nov 19, 2020 3:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: sapling q 5
Replies: 4
Views: 48

### Re: sapling q 5

From my understanding, axial atoms are located at the poles, at the top and bottom of a structure. Equatorial atoms would be located on the plane horizontal to the central atom. For example, in the structure of SF4, the lone pair would be on the equatorial plane to minimize the number of 90 degree b...
Thu Nov 19, 2020 3:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape Names
Replies: 50
Views: 299

### Re: Shape Names

Yes, and keep in mind that the shape is also called bent when referencing a molecule with two bonds and one lone pair. For example, Sulfur dioxide would have a trigonal planar electron pair geometry and a bent molecular geometry.
Wed Nov 18, 2020 3:43 pm
Forum: General Science Questions
Topic: Which would have lower ionization energy?
Replies: 13
Views: 118

### Re: Which would have lower ionization energy?

I asked a question similar to this during a UA Session last week, and the UA told me that we wouldn't be tested on "diagonals", like Chlorine and Oxygen because the trends for diagonals are a little ambiguous. Comparisons made during exams would be much more obvious or predictable.
Wed Nov 18, 2020 3:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Arrangement of Electrons = Electron Pair Geometry
Replies: 2
Views: 31

### Arrangement of Electrons = Electron Pair Geometry

Hi just to clarify, when Dr. Lavelle mentions the arrangement of the electron regions, is he is referencing electron pair geometry? Just wanted to make sure because in high school we learned VSEPR Theory as two separate parts, electron pair geometry and molecular geometry, and molecular geometry has...
Mon Nov 16, 2020 10:50 am
Forum: Bond Lengths & Energies
Topic: F2 Bond Strength
Replies: 6
Views: 48

### Re: F2 Bond Strength

Hello! If you are comparing the bond strength of diatomic halogens, we can compare F2 to Cl2. The bond dissociation energy of F2 is less than Cl2 because fluorine has a high electronegativity, resulting in F−F repelling each other and having lesser bond dissociation enthalpy than Cl2 since Cl is le...
Mon Nov 16, 2020 10:33 am
Forum: Bond Lengths & Energies
Topic: F2 Bond Strength
Replies: 6
Views: 48

### F2 Bond Strength

Could someone please explain why the bond between two F2 molecule is so weak compared to other bonds? It seems like it would be strong because fluorine is small and would have short bonds.
Sun Nov 15, 2020 6:50 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook Problem 1.E.25
Replies: 7
Views: 73

### Re: Textbook Problem 1.E.25

I had the same issue, thank you everyone!
Sun Nov 15, 2020 6:48 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook 1E.25
Replies: 1
Views: 14

### Re: Textbook 1E.25

Hi Alison, to give the electron configuration for a group of multiple atoms, use the variable "n" to state the energy level. For example, for part a, the valence configuration of the alkali metals would be ns^1.
Thu Nov 12, 2020 5:24 pm
Forum: Trends in The Periodic Table
Topic: N 3- vs S 2-
Replies: 4
Views: 41

### N 3- vs S 2-

So if a question asked about comparing atomic radius of Nitrogen 3- to Sulfur 2-, which would be larger? Would the shielding effect of Sulfur have a greater effect than the extra electron on Nitrogen?
Thu Nov 12, 2020 8:29 am
Forum: Lewis Structures
Replies: 12
Views: 38

It's pretty easy to see when a molecule is a radical. When you make the lewis structure and there's an odd total number of electrons or the charge isn't what it's supposed to be, those are pretty clear indicators.
Thu Nov 12, 2020 8:26 am
Forum: Coordinate Covalent Bonds
Topic: When do we use it
Replies: 9
Views: 59

### Re: When do we use it

If you're drawing a Lewis Structure and a molecule doesn't have enough electrons to make a complete octet but its still relatively stable, like BF3, that would be a great candidate for a coordinate covalent bond. If a molecule with a free lone pair is there, like F- or ammonia, NH3, that molecule wo...
Wed Nov 11, 2020 9:35 am
Forum: Administrative Questions and Class Announcements
Topic: Chemistry Community Points [ENDORSED]
Replies: 4
Views: 371

### Chemistry Community Points[ENDORSED]

Just to clarify, do we only earn points for posts made on topics from current lectures? Like if I posted a question about quantum mechanics today, would it count towards Chemistry community points?
Wed Nov 11, 2020 7:18 am
Forum: Electronegativity
Topic: Noble Gases
Replies: 40
Views: 1778

### Re: Noble Gases

Would noble gases follow the trend for first ionization energy? It seems like it would take a lot of energy to remove an electron from the full valence shell.
Wed Nov 11, 2020 7:13 am
Forum: Resonance Structures
Topic: Hybrid structures
Replies: 2
Views: 22

### Re: Hybrid structures

It is, that's one of the main limitations of Lewis Structures. Lewis Structures make it look like there is one double bond and one single bond in NO2, but in actuality, both bonds are the same length and double bond character is spread between both bonds. The bond length and strength would be in bet...
Tue Nov 10, 2020 12:30 pm
Forum: Bond Lengths & Energies
Replies: 5
Views: 157

A radical is a molecule that contains at least one unpaired electron. In organic chemistry, it is more specified that radical stability increases in the order methyl < primary < secondary < tertiary, but I'm not sure how much of this we actually need to know. The stability of radicals on the carbon...
Tue Nov 10, 2020 12:20 pm
Forum: Dipole Moments
Topic: melting point
Replies: 4
Views: 40

### Re: melting point

While both molecules exhibit London Dispersion Forces, butanol has hydrogen bonding capabilities due to the -OH group at the end of the molecule. The strength of a hydrogen bond is higher than an ion-dipole interaction and lower than an ion-ion interaction. Thus, hydrogen bonding would be stronger ...
Sun Nov 08, 2020 12:43 pm
Forum: Administrative Questions and Class Announcements
Topic: Question for Students about High School Chem
Replies: 25
Views: 122

### Re: Question for Students about High School Chem

I took AP Chemistry during senior year, and we went over bonding in great detail, but we never talked about quantum mechanics or the properties of light. Those two topics were entirely new to me. I would advise Khanacademy or Youtube videos to have an introduction to the harder units, such as Chemic...
Fri Nov 06, 2020 10:28 am
Forum: Coordinate Covalent Bonds
Topic: H20 Example from Lecture today
Replies: 4
Views: 49

### H20 Example from Lecture today

Since OH- is a Lewis base and supplies both of the electrons in the formation of water, is the formation of water from H+ and OH- a coordinate covalent bond?
Thu Nov 05, 2020 2:06 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 1 Review
Replies: 7
Views: 56

### Re: Midterm 1 Review

905409193 wrote:I want to review the questions but I don't really remember what the questions were so how would I look for them in the textbook?

I feel the same way, it's been about 9 days since my exam and I don't remember the problems.
Wed Nov 04, 2020 2:33 pm
Forum: Student Social/Study Group
Topic: How many points for an A and above?
Replies: 10
Views: 139

### Re: How many points for an A and above?

Megan Singer 1F wrote:I would assume an A is the standard 90%, which is 450 points. If you're asking about a 4.0 (A and A+), that's usually cut off at 93% or 465 points.

Does anyone know why our class uses this grading system? It seems like it works the same way as the 0-100 system but at a larger scale of points.
Wed Nov 04, 2020 2:31 pm
Forum: Student Social/Study Group
Topic: Favorite TV shows
Replies: 178
Views: 884

### Re: Favorite TV shows

Seinfeld! I really love sitcoms and sitcoms from the 1980s-2000s are the best. Friends and The Office are a close second, I know these are pretty basic.
Wed Nov 04, 2020 2:29 pm
Forum: Student Social/Study Group
Topic: Unexpected Result of using Chemistry Communtiy
Replies: 7
Views: 81

### Unexpected Result of using Chemistry Communtiy

As a result of using Chemistry Community over the past four weeks, I've been able to memorize my UCLA UID :) . I guess a lot of other people are the same way.
Mon Nov 02, 2020 11:18 am
Forum: Resonance Structures
Topic: How are bond lengths measured experimentally?
Replies: 2
Views: 44

### How are bond lengths measured experimentally?

How are bond length's measured experimentally? Dr. Lavelle mentioned electron diffraction but I'd like to know a little more about it.
Mon Nov 02, 2020 11:17 am
Forum: Resonance Structures
Topic: Delocalization of electrons
Replies: 10
Views: 78

### Re: Delocalization of electrons

Do delocalized electrons contribute to conductivity?
Sat Oct 31, 2020 5:40 pm
Forum: Ionic & Covalent Bonds
Topic: Constants
Replies: 5
Views: 77

### Re: Constants

Follow up question, do we need to print out a new formula sheet for the next midterm if we wrote on the formula sheet?
Sat Oct 31, 2020 5:37 pm
Forum: Trends in The Periodic Table
Topic: Metalloids/Non-Metals on the Periodic Table
Replies: 6
Views: 31

### Re: Metalloids/Non-Metals on the Periodic Table

I think the best way to remember which elements are metalloids are by memorizing them. Since there are only seven of them on our periodic table, I don't think it would be too hard to memorize them with a mnemonic such as: Boring Silly Goats Are At The Party (Boron, Silicon, Germanium, Arsenic, Anti...
Sat Oct 31, 2020 5:34 pm
Forum: Ionic & Covalent Bonds
Topic: Is ionic or covalent stronger?
Replies: 31
Views: 393

### Re: Is ionic or covalent stronger?

I've heard ionic bonds are stronger, but certain types of covalent bonds may be stronger than an ionic bond. For example, the triple bond between two nitrogen atoms is extremely strong and takes about 900 kJ/mol to break.
Sat Oct 31, 2020 5:31 pm
Forum: Trends in The Periodic Table
Topic: Oxygen and Ionization Energy
Replies: 9
Views: 43

### Re: Oxygen and Ionization Energy

I think its because since oxygen has more electron-electron repulsions than nitrogen, it has a lower ionization energy. For fluorine, fluorine has a higher effective nuclear charge and holds onto its electrons stronger than oxygen does.
Wed Oct 28, 2020 2:07 pm
Forum: Administrative Questions and Class Announcements
Replies: 4
Views: 50

Normally you would be given the solutions at the end of the workshop or you could email the UA for the solutions afterwards. But this would only be for workshops you attended. Sometimes the UA's use questions from old midterms or finals and aren't able to release them.
Wed Oct 28, 2020 12:11 pm
Forum: Trends in The Periodic Table
Topic: Question about 2nd Ionization Energy Fact
Replies: 2
Views: 33

### Re: Question about 2nd Ionization Energy Fact

Thank you Zaid!
Wed Oct 28, 2020 10:53 am
Forum: Trends in The Periodic Table
Topic: Question about 2nd Ionization Energy Fact
Replies: 2
Views: 33

### Question about 2nd Ionization Energy Fact

Dr. Lavelle mentioned in lecture today that the 2nd ionization energy for all elements in the gas phase is higher than the first ionization energy. I was a little confused about this, because for the alkaline earth metals like magnesium, wouldn't those elements want to lose two electrons? After losi...
Mon Oct 26, 2020 7:20 pm
Forum: Properties of Electrons
Topic: Energy emitted per grams of atoms.
Replies: 2
Views: 17

### Re: Energy emitted per grams of atoms.

Don't forget to convert to grams before dividing by molar mass!
Mon Oct 26, 2020 6:55 pm
Forum: Photoelectric Effect
Topic: Need help with Experiment Conclusions
Replies: 3
Views: 47

### Need help with Experiment Conclusions

So if I'm correct, the experiment where they shot electrons through slits and saw interference and diffraction, proving the wave model of electrons. The photoelectric effect showed the particle model of light because increasing intensity at the same wavelength didn't eject electrons while a higher f...
Sun Oct 25, 2020 7:04 pm
Forum: Administrative Questions and Class Announcements
Topic: CCLE website
Replies: 12
Views: 79

### Re: CCLE website

It was down for about 6 hours, which is really inconvenient, especially considering its midterm week.
Sun Oct 25, 2020 7:02 pm
Forum: Administrative Questions and Class Announcements
Topic: CCLE DOWN
Replies: 6
Views: 74

### Re: CCLE DOWN

I saved mine as a bookmark so I always use that to go to Sapling directly and not through CCLE. You should be able to just search Sapling and log in from their end because their website isn't down. How are you able to access Sapling directly? Whenever I log in through CCLE it always works, but when...
Sat Oct 24, 2020 6:37 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Replies: 5
Views: 40

### Re: 1B.28 Question about Mass

Hi, to find the mass of a Li+ atom, you are right in that you would divide the molar mass of Lithium by Avogadro's number because the units would cancel out to get grams/ion. You would then divide that number by 1000 to get the mass in kg/atom which can be plugged into the heisenberg uncertainty eq...
Sat Oct 24, 2020 6:15 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Confusion with Uncertainty Values
Replies: 7
Views: 69

### Re: Confusion with Uncertainty Values

Uncertainty is mainly about the range of values that the real value could be in. The actual value of the velocity doesn't really matter. For the question you specified, the uncertainty in velocity would be 4 m/s.
Sat Oct 24, 2020 6:12 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Replies: 5
Views: 40

1B.28 The uncertainty principle has negligible consequences for macroscopic objects. However, the properties of nanoparticles, which have dimensions ranging from a few to several hundred nanometers, may be different from those of larger particles. (a) Calculate the minimum uncertainty in the speed o...
Thu Oct 22, 2020 5:01 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Hydrogen Emission Spectrum
Replies: 3
Views: 46

### Re: Hydrogen Emission Spectrum

You are given the frequency of the light, which you can use to find the type of light that was used. Using the equation c=lamda x frequency, the wavelength is 4.84x10^-7 m, which corresponds to blue/violet light. Since the Balmer series used visible light you can conclude that the n initial is n=2. ...
Wed Oct 21, 2020 7:59 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1B.5 Example from Step-Up Sessions Confusion
Replies: 2
Views: 31

### Re: 1B.5 Example from Step-Up Sessions Confusion

Chem_Mod wrote:The uncertainty in velocity is the range. Therefore, we must take the 0.001 m/s and multiply it by 2 between the velocity can be 0.001 m/s above or below the velocity. This will give us the uncertainty in velocity.

Thank you! That makes so much more sense.
Wed Oct 21, 2020 5:46 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1B.5 Example from Step-Up Sessions Confusion
Replies: 2
Views: 31

### 1B.5 Example from Step-Up Sessions Confusion

During a step-up session we went over Example 1B.5 from the textbook (this was an example from the chapter, not from the exercises), and the question said "Estimate the minimum uncertainty in a) the position of a marble of mass 1.0 g given that its speed is known to within +/- 1.0 mm/s and b) t...
Mon Oct 19, 2020 3:07 pm
Forum: Balancing Chemical Reactions
Topic: L.35 Balancing Third Equation
Replies: 4
Views: 47

### Re: L.35 Balancing Third Equation

The error messed me up as well. The balanced equation is Fe3Br8 + 4Na2Co3 yields 8 NaBr + 4CO2 + Fe3O4. Hope this helps!
Mon Oct 19, 2020 11:54 am
Forum: DeBroglie Equation
Topic: De Broglie Equation Application
Replies: 5
Views: 49

### Re: De Broglie Equation Application

Thank you everyone! Your responses helped a lot!
Mon Oct 19, 2020 11:14 am
Forum: DeBroglie Equation
Topic: De Broglie Equation Application
Replies: 5
Views: 49

### De Broglie Equation Application

I'm a little confused by where we can apply the De Broglie Equation. Is it only applicable in situations where the particle/object has measurable mass? In other words, is the equation usable for light, or only for electrons and larger objects?
Mon Oct 19, 2020 10:34 am
Forum: DeBroglie Equation
Topic: De Broglie Equation cut off
Replies: 6
Views: 54

### Re: De Broglie Equation cut off

Dr. Lavelle addressed this in today's lecture. A wavelength smaller than 10^-15 is undetectable, while wavelengths higher than 10^-15 is detectable.
Mon Oct 19, 2020 10:21 am
Forum: DeBroglie Equation
Topic: Units in Solving Questions regarding De Broglie Equation
Replies: 4
Views: 44

### Units in Solving Questions regarding De Broglie Equation

In the lecture from today, 10/19, Dr. Lavelle worked out a question where a car, weighing 1500 kg travelled at 27 m/s, and we had to find the De Broglie Wavelength. In terms of units, Planck's Constant is in Joule seconds, mass is in kilograms, and velocity is in meters per second. This question wor...
Sun Oct 18, 2020 3:25 pm
Forum: Properties of Light
Topic: Work Function Question
Replies: 6
Views: 51

### Re: Work Function Question

Kushaal_Madadi_2G wrote:Did anyone else look at the symbol for work function and think that it looked like the Elder Wand and the Stone of Resurrection from the Deathly Hallows in Harry Potter? lol.

I thought so too :). It just needed the triangle around it.
Sun Oct 18, 2020 2:08 pm
Forum: Administrative Questions and Class Announcements
Replies: 2
Views: 23

### Re: iPad for Midterm Work

Charisma Arreola 2L wrote:I believe you will because I am currently doing the same thing. My TA said as long as I have an external webcam for the zoom during the midterm, I should be fine.

Thank you!
Sun Oct 18, 2020 2:02 pm
Forum: Administrative Questions and Class Announcements
Replies: 2
Views: 23

Hello, so I use an iPad to take notes during lectures and to work out practice and homework problems. Would I be allowed to use the iPad to work out questions during midterms and the final?
Sun Oct 18, 2020 10:07 am
Forum: Properties of Light
Topic: Work Function Question
Replies: 6
Views: 51

### Work Function Question

In the equation E(photon) - E(energy to remove electron) = E (excess), is the E(energy to remove electron) also writable as the work function? Just needing a bit of clarification, since it seems like the energy to remove an electron would be synonymous with the threshold energy.
Fri Oct 16, 2020 12:00 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Light Emitted
Replies: 2
Views: 40

### Re: Light Emitted

I think you're right. I remember Dr. Lavelle mentioning that the filament in the lightbulb is making the light, and I assume the metal used can be varied to change the color of light produced. I would assume we only see the most prevalent color, like how the neon in the demo today was red, and the o...