Search found 106 matches

Thu Jan 14, 2021 11:16 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: net ionic equations
Replies: 4
Views: 22

Re: net ionic equations

I was also wondering the same thing, but I'm fairly certain that we don't have to worry too much about net ionic equations (for now at least). In general, though, I do believe you're correct that we should only dissociate the aqueous solutions and leave the solids/liquids alone. We would probably be...
Wed Jan 13, 2021 12:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Concentrations and Solubility
Replies: 3
Views: 19

Equilibrium Concentrations and Solubility

Hey guys, I was wondering how we would use equilibrium concentrations to predict the solubility of a substance. The reason I ask is that this is one of the bullet points on the outline for the chemical equilibrium unit, and I'm unsure of how solubility relates to the value for K. Do we look at how m...
Tue Jan 12, 2021 10:04 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Neglecting Water
Replies: 20
Views: 84

Re: Neglecting Water

Another example that makes it easier to understand why we ignore water in the equilibrium expression is by thinking about a bank account filled with a million dollars. If you were to withdraw ten dollars out of that account, you would still basically have a million dollars. Thus, the change in water...
Tue Jan 12, 2021 9:58 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook Problem 5H.3
Replies: 3
Views: 15

Re: Textbook Problem 5H.3

I definitely agree with the other answer and would add that it's important to keep in mind rules regarding the K value. For instance, multiplying a reaction by some factor (so that its stoichiometric coefficients are multiplied) would make the equilibrium constant be raised to the power of that numb...
Mon Jan 11, 2021 1:27 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Principle Explanation
Replies: 4
Views: 29

Re: Principle Explanation

I agree with the other answer and would just add that it's really helpful to understand what exactly Le Chatelier's Principle is saying. It basically states that a reaction wants to minimize the effect of any change. Keeping this in mind, we can better understand questions that describe a certain ch...
Mon Jan 11, 2021 1:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #4
Replies: 7
Views: 64

Re: Sapling #4

Yes, that's the equation you should use. I think it's important to remember that the Kc and Kp expressions are basically very similar, we just have to know when to distinguish between the two based on whether the given compositions are concentrations or pressures. In addition, it's helpful to know t...
Mon Jan 11, 2021 1:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Difference between Amphoteric and Amphiprotic
Replies: 5
Views: 30

Re: Difference between Amphoteric and Amphiprotic

I definitely agree with the other answers and would just add that an easy way to distinguish between the two is by looking for a hydrogen atom. Amphiprotic compounds must have an H+ to donate, so if it doesn't then this automatically means it cannot be amphiprotic. However, it can still be amphoteri...
Mon Jan 11, 2021 1:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ATP Hydrolysis and Osmotic Pressure
Replies: 3
Views: 22

ATP Hydrolysis and Osmotic Pressure

Hey guys, I had a question for one of the bullet points on the outline for this unit. It states that we have to know about "Biological examples. For example: ATP hydrolysis, osmotic pressure." Would anyone be able to give an overview regarding this topic? I don't remember Dr. Lavelle expla...
Thu Jan 07, 2021 10:46 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Why doesn't pressure change affect K?
Replies: 5
Views: 30

Why doesn't pressure change affect K?

Hey guys, I was wondering if anyone could help explain why a change in pressure doesn't affect the equilibrium constant. The reason I ask this is because a compression can shift a reaction to favor the products (for example) and this would mean that there would be a higher ratio of products compared...
Wed Jan 06, 2021 12:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Self-Test 5G.1A
Replies: 4
Views: 25

Re: Self-Test 5G.1A

Yeah, so basically water isn't included in an equilibrium constant when it is in its liquid state. This is because it's in a phase where a concentration change wouldn't lead to much of a difference before and after the reaction. An example Dr. Lavelle used was imagining if you take out 10 dollars fr...
Wed Jan 06, 2021 12:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Will adding a solid reactant increase the amount of product?
Replies: 6
Views: 47

Re: Will adding a solid reactant increase the amount of product?

Okay, that definitely makes sense. I was a bit confused because I knew that the amount of reactants in general would change, but at the same time the actual value of K doesn't take solids into account. However, it makes sense that having more reactants would ultimately lead to increased products, ev...
Tue Jan 05, 2021 12:42 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Will adding a solid reactant increase the amount of product?
Replies: 6
Views: 47

Will adding a solid reactant increase the amount of product?

Hey guys, I was wondering whether or not increasing the amount of solid reactants in a reaction will lead to an increase in the products. The reason I ask is because solids are not included in the equilibrium expression, so increasing them won't make Q less than K (for it to then counteract by produ...
Tue Jan 05, 2021 12:33 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Reactant in Excess
Replies: 9
Views: 39

Re: Reactant in Excess

I think it's just really important to always remember that adding a reactant or product at any time will ultimately not change the equilibrium constant. The reaction will always work to return to that same ratio even if you start out with or add additional reactants, so in this case I believe that K...
Tue Jan 05, 2021 12:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant in terms of stability
Replies: 4
Views: 32

Re: Equilibrium Constant in terms of stability

I definitely agree with the other answers and would just add that Lewis Structures are particularly useful for understanding K values. Whenever we have a very low equilibrium constant, this means that the reactants don't really prefer to become products and thus they are more stable in the initial f...
Mon Jan 04, 2021 12:52 pm
Forum: Ideal Gases
Topic: Converting to Concentration and Pressure Values
Replies: 7
Views: 64

Re: Converting to Concentration and Pressure Values

I agree with the other answer and would just add that this calculation is necessary if (for example) we are given equilibrium concentrations of a reaction but are asked to find the Kp value, which uses partial pressures. The ideal gas law thus allows us to convert between concentrations and partial ...
Mon Jan 04, 2021 12:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pure substances in equilibrium expressions
Replies: 3
Views: 22

Re: Pure substances in equilibrium expressions

Oh okay, that definitely makes sense. I now understand that solids aren't dissolved so we can't really think about them in terms of concentration. That explains what Dr. Lavelle meant when he was explaining how leftover solid in a reaction isn't taken into account (because it remains undissolved). A...
Mon Jan 04, 2021 12:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pure substances in equilibrium expressions
Replies: 3
Views: 22

Pure substances in equilibrium expressions

Hey guys, I was watching today's lecture and got a bit confused when Dr. Lavelle was discussing how pure substances like solids and liquids are not supposed to be included in the expression for K. I understand that we can't really think about their concentrations changing, but why is that? I hope my...
Thu Dec 10, 2020 12:32 pm
Forum: Lewis Acids & Bases
Topic: Identifying Lewis Acids and Bases
Replies: 3
Views: 44

Identifying Lewis Acids and Bases

Hey guys, I was wondering if someone could give any tips for identifying Lewis Acids and Bases whenever we are given two molecules that react. I understand their definition and can distinguish between them usually, but in some examples it seems a bit more unclear and I have trouble telling which is ...
Wed Dec 09, 2020 12:22 pm
Forum: Bronsted Acids & Bases
Topic: Respiratory Acidosis
Replies: 1
Views: 33

Respiratory Acidosis

Hey guys, I was looking over the outline for the Acids & Bases section and noticed that the last bullet point said "Explain how carbon dioxide can lead to respiratory acidosis." Would anyone be able to quickly go over what we should know about this topic? I know Dr. Lavelle discussed t...
Tue Dec 08, 2020 12:49 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelates
Replies: 2
Views: 47

Re: Chelates

I agree with the other answer and would just add that chelates usually have a lone pair-spacer-spacer-lone pair pattern when drawing out its structure, so this can be used to judge whether a polydentate is actually going to act as a chelate or not. I believe that all chelates have to be polydentate,...
Tue Dec 08, 2020 12:44 pm
Forum: Bronsted Acids & Bases
Topic: Net Ionic Equations
Replies: 4
Views: 39

Re: Net Ionic Equations

Okay, that definitely makes sense. I think I have a better understanding now that Dr. Lavelle explained the example with Na+ when writing equations with acids and bases, I just wanted to make sure if we had to practice them for the final or not. That really helped, thank you all!
Mon Dec 07, 2020 10:55 am
Forum: Determining Molecular Shape (VSEPR)
Topic: flat plane vs 3D
Replies: 2
Views: 20

Re: flat plane vs 3D

I think that molecules with only two or three regions of electron density would in fact be only "planar" or flat. However, I believe that some planar molecules would not actually be flat because they'd have lone pairs that aren't on that 2D plane. An example is square planar or t-shaped mo...
Mon Dec 07, 2020 10:48 am
Forum: Bronsted Acids & Bases
Topic: Net Ionic Equations
Replies: 4
Views: 39

Net Ionic Equations

Hey guys, I was wondering whether or not we had to know how to write net ionic equations for reactions with acids and bases. It's a topic that I don't really understand well and so was wondering whether I should review it. If it is something that we should know, does anyone have any tips on how to w...
Mon Dec 07, 2020 10:43 am
Forum: Bronsted Acids & Bases
Topic: Carboyxl group
Replies: 4
Views: 43

Re: Carboyxl group

I agree with the previous answer and would just like to add that seeing a carboxyl group indicates that it's a weak acid, not a strong one, so that's definitely something to keep in mind. However, the COOH carboxyl group is stronger than a molecule with just an -OH group because the increased oxygen...
Mon Dec 07, 2020 10:40 am
Forum: Lewis Acids & Bases
Topic: Week 10 Sapling #6
Replies: 2
Views: 31

Re: Week 10 Sapling #6

I would definitely agree with the other answer and add as a guide that most derivatives of ammonia are usually going to be weak bases as well. In addition, strong acids usually have two more oxygen atoms than hydrogen atoms, which accounts for HClO3 and HClO4 being strong acids while HClO and HClO2 ...
Thu Dec 03, 2020 10:08 am
Forum: Bronsted Acids & Bases
Topic: Why is HF a weak acid?
Replies: 5
Views: 81

Re: Why is HF a weak acid?

Okay, that definitely makes sense. I was assuming that HF doesn't dissociate completely because the bond between H and F is so short and thus strong. That makes it easier to generally understand the difference between strong and weak acids. Also, I didn't know that very concentrated solutions of HF ...
Wed Dec 02, 2020 11:34 am
Forum: Bronsted Acids & Bases
Topic: Why is HF a weak acid?
Replies: 5
Views: 81

Why is HF a weak acid?

Hey guys, I was looking at a list of strong and weak acids and noticed that HF is considered to be weak. I was a bit confused because I know that HCl and HBr are both strong acids. I was wondering if anyone could explain why this particular acid is weak while other halogens that bind with hydrogen a...
Tue Dec 01, 2020 12:01 pm
Forum: Sigma & Pi Bonds
Topic: Delocalized pi bonds
Replies: 2
Views: 37

Re: Delocalized pi bonds

Delocalized pi bonds occur in benzene, for example, when each carbon atom has one unhybridized p-orbital. Because each carbon atom is the same distance apart from each other, the unhybridized orbitals aren't really bonding in a way where we can observe separate double and single bonds in the molecul...
Tue Dec 01, 2020 11:58 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Learning ligand names and charges
Replies: 5
Views: 76

Re: Learning ligand names and charges

Okay, that definitely makes sense. I was also thinking that memorizing them would just make answering questions a lot easier. I believe Dr. Lavelle will probably specify which ones we have to learn in a future lecture so once we know which are the most important ones we can start to do so. That defi...
Mon Nov 30, 2020 11:24 am
Forum: Biological Examples
Topic: Hemoglobin vs. Myoglobin
Replies: 29
Views: 215

Re: Hemoglobin vs. Myoglobin

I remember Dr. Lavelle saying that hemoglobin is made up of four myoglobin-like molecules, so does that mean they detach from hemoglobin to form myoglobin? I'm not sure whether this is the case. If anyone has an idea that would be really helpful, I'm a bit confused as to how myoglobin forms as compa...
Mon Nov 30, 2020 11:19 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: EDTA+
Replies: 2
Views: 38

Re: EDTA+

If I'm not mistaken, the ability to form a ring is basically referencing how chelates form and integrate the central TM cation as a part of it. In addition, I remember that Dr. Lavelle said that these ligands can rotate in this manner because they have single bonds. Single, or sigma, bonds can rotat...
Mon Nov 30, 2020 11:04 am
Forum: Hybridization
Topic: Valence Bond Theory
Replies: 2
Views: 43

Re: Valence Bond Theory

I was also wondering about this topic, but I think the other answer definitely addressed it well. I believe that a good way to approach Valence Bond Theory is by just thinking about how we visualize bonds between atoms. For example, covalently bonded atoms have electrons in the shared region between...
Mon Nov 30, 2020 10:57 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Learning ligand names and charges
Replies: 5
Views: 76

Learning ligand names and charges

Hey guys, I'm currently looking at Dr. Lavelle's sheet going over ligand names in coordination compounds that he provides on his website, and I'm wondering whether we should start to memorize some of the more unfamiliar ones. Is it a good idea to remember which ligands are polydentates? Or is it fin...
Thu Nov 26, 2020 1:19 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: How to tell whether a ligand is polydentate
Replies: 2
Views: 36

Re: How to tell whether a ligand is polydentate

Yeah, that makes sense. I remember in the previous lecture Dr. Lavelle said that double bonds can't rotate because the pi bonds aren't located on the internuclear axis, so I get why the polydentate ligand would have to have single bonds. That definitely helped, thank you!
Wed Nov 25, 2020 11:39 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: How to tell whether a ligand is polydentate
Replies: 2
Views: 36

How to tell whether a ligand is polydentate

Hey guys, I was watching today's lecture and I think that I got a good understanding of what polydentates are and how they form. However, I was just wondering how exactly we would know whether or not a molecule is polydentate or not. If a question gives us the formula of a molecule, would we have to...
Tue Nov 24, 2020 10:07 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Do we ever need these values backwards? Like polarizability of cations / polarizing power of anions?
Replies: 3
Views: 39

Re: Do we ever need these values backwards? Like polarizability of cations / polarizing power of anions?

I believe that since cations usually have a lower electronegativity than anions, they don't exactly have extra valence electrons in the ionic bond for the anion to distort. This basically means there wouldn't really be much to polarize on a cation due to its lower electronegativity. In general, thou...
Tue Nov 24, 2020 10:00 am
Forum: Hybridization
Topic: Why are lone pairs hybridized?
Replies: 4
Views: 58

Re: Why are lone pairs hybridized?

Ohh, that definitely makes sense! I understand now that the fact that lone pair electrons partly determine the electron arrangement means they do have to be hybridized. I didn't realize that their importance for determining VSEPR shape and interactions could be the reason why we think about them in ...
Mon Nov 23, 2020 11:38 am
Forum: Lewis Structures
Topic: Predicting Molecular Shapes
Replies: 3
Views: 26

Re: Predicting Molecular Shapes

I definitely agree with the other answers and would just add that it's important to keep in mind that lone pairs repel each other and atoms more than atoms repel each other. This means we have to keep lone pairs as far from each other as possible, because they have the strongest repulsion. This is i...
Mon Nov 23, 2020 11:28 am
Forum: Hybridization
Topic: Why are lone pairs hybridized?
Replies: 4
Views: 58

Why are lone pairs hybridized?

Hey guys, I had a question regarding lone pairs when it came to hybridization. I know we use hybridization to explain the observed electron arrangement in the VSEPR model, but I'm having a bit of trouble understanding why exactly we have to consider that lone pairs in an orbital are hybridized. If t...
Mon Nov 23, 2020 11:23 am
Forum: Hybridization
Topic: Unhybridized p orbital
Replies: 2
Views: 51

Re: Unhybridized p orbital

I was wondering this as well, because I wasn't sure if a double bond could involve unhybridized d-orbitals instead of p-orbitals. I'm still not entirely sure, but I don't believe there would be any situation in which this is the case. I think especially since we focus mostly on sp, sp2, and sp3 orbi...
Mon Nov 23, 2020 11:18 am
Forum: Coordinate Covalent Bonds
Topic: How?
Replies: 3
Views: 78

Re: How?

I agree with the other answer and would like to add that coordinate covalent bonds often form whenever the Lewis acid has an atom with an incomplete octet. An example is BF3. Because boron has an incomplete octet in this molecule, we can assume that it will in fact willingly accept the electron pair...
Thu Nov 19, 2020 10:18 am
Forum: Octet Exceptions
Replies: 5
Views: 88

Okay, that makes sense. I was also confused with that example, because I'd expect oxygen to have the radical and thus allow for a formal charge of 0 for both atoms. However, I guess that in this situation we just attach the radical to whichever atom is less electronegative like you said. I also see ...
Wed Nov 18, 2020 11:53 am
Forum: Octet Exceptions
Replies: 5
Views: 88

Hey guys, I had a question about octet exceptions. Whenever a molecule has a radical, how do we decide which atom gets that one electron? I think we would have to use formal charge, but I'm still unsure because I don't know if we would still have to use that process. If someone could give advice for...
Tue Nov 17, 2020 10:33 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability and Polarizing Power
Replies: 5
Views: 31

Re: Polarizability and Polarizing Power

I would also add that cations become more polarizing (or better at distorting the cloud of the anion it gets near) when they're smaller and have a more positive charge. This means that as you move up and to the right on the periodic table, cations become more polarizing. Meanwhile, anions become mor...
Tue Nov 17, 2020 10:27 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Factors Affecting Electron Energy in Multi-Electron Atom
Replies: 5
Views: 48

Re: Factors Affecting Electron Energy in Multi-Electron Atom

Yeah, the fact that shielding is going to affect the energy of the electrons in multi-electron atoms seems to be important, and it definitely makes sense. I also found that older post to be helpful, as it explained how both shielding and the presence of nodes are going to be the reason why we don't ...
Mon Nov 16, 2020 11:00 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Factors Affecting Electron Energy in Multi-Electron Atom
Replies: 5
Views: 48

Factors Affecting Electron Energy in Multi-Electron Atom

Hey guys, I was going over the quantum section to review for this week's midterm and I realized I was a bit confused about one of the topics. Specifically, it's the bullet point on outline 2 that says "Describe the factors affecting the energy of an electron in a multi-electron atom." Does...
Mon Nov 16, 2020 10:54 am
Forum: Trends in The Periodic Table
Topic: Oxygen Exception Ionization Energy
Replies: 12
Views: 87

Re: Oxygen Exception Ionization Energy

I think we learned about this exception when covering trends in the periodic table. It was mentioned when the textbook talked about ionization energy, electron affinity, atomic radius, etc. In lecture, I think Dr. Lavelle talked about this rule for oxygen in lecture 12 (since that was the one that c...
Mon Nov 16, 2020 10:43 am
Forum: Trends in The Periodic Table
Topic: Oxygen Exception Ionization Energy
Replies: 12
Views: 87

Re: Oxygen Exception Ionization Energy

I believe that a big part of this is because fluorine is a halogen. Because its electron affinity is so high, this discrepancy that we see in oxygen when it comes to ionization energy doesn't really happen in group 17 elements. The way I think about this exception is that we only pay attention to it...
Mon Nov 16, 2020 10:37 am
Forum: Electronegativity
Topic: Homework Problem 3F.5
Replies: 7
Views: 96

Re: Homework Problem 3F.5

For this problem, it's important to keep in mind which intermolecular forces these molecules will have. For example, the London forces in a molecule of NaCl are going to be stronger than the London forces in HCl, because larger atoms are more polarizable (since their increased electrons make it easi...
Thu Nov 12, 2020 9:47 am
Forum: Lewis Structures
Topic: Line structures
Replies: 3
Views: 25

Re: Line structures

Ohh okay that definitely makes sense. I knew it had to do with the simplified form of the benzene ring that we looked at in class but I wasn't entirely sure, so I wanted to check. I'll just assume that whenever there's a line with no atom attached at a corner, then it's meant to signify a carbon ato...
Wed Nov 11, 2020 9:55 am
Forum: Lewis Structures
Topic: Line structures
Replies: 3
Views: 25

Line structures

Hey guys, I had a question about one of the bullet points on this unit's outline. It says, "Draw line structures of organic compounds." I was a bit confused as to what exactly this means. Are line structures different from Lewis structures? And if so, is there a particular process we have ...
Tue Nov 10, 2020 10:15 am
Forum: Resonance Structures
Topic: oxidation numbers in regards to resonance
Replies: 2
Views: 28

Re: oxidation numbers in regards to resonance

I was also confused about this problem. However, like the other answer stated, using oxidation number to determine the most likely structure requires you to find the Lewis Structure in which formal charge is closest to the oxidation number you found. But this can be misleading, like in this problem....
Tue Nov 10, 2020 10:11 am
Forum: Octet Exceptions
Topic: Group 13
Replies: 3
Views: 45

Re: Group 13

Yeah, I agree with the other answers. I was also previously wondering whether this was the case for group 13 elements. However, Dr. Lavelle explained that because they only have 3 valence electrons, it's hard for them to complete an octet since this would require 5 electrons to be accepted. This is ...
Mon Nov 09, 2020 11:02 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Does polarizability increase left to right?
Replies: 4
Views: 32

Re: Does polarizability increase left to right?

Yeah, that definitely makes sense. If polarizability decreases as you move up and right on the periodic table, then anions with more charge (moving left across a period) will be more polarizable. That really helped, thank you!
Mon Nov 09, 2020 10:01 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Does polarizability increase left to right?
Replies: 4
Views: 32

Does polarizability increase left to right?

Hey guys, I know that the polarizability of anions increases as you move down a group in the periodic table because the electrons of that anion are further away from the nucleus (and thus it's harder to maintain them). However, I was wondering whether polarizability increases as you move to the left...
Mon Nov 09, 2020 9:55 am
Forum: Resonance Structures
Topic: structure of lower energy
Replies: 5
Views: 17

Re: structure of lower energy

Yeah, that is exactly what you would have to do in this situation. Since the lowest formal charges on the atoms would indicate that the atoms are more stable (and in general lower in energy), you have to use the formal charge equation FC = V - (1/2S + L) to distinguish between the possible Lewis Str...
Mon Nov 09, 2020 9:43 am
Forum: Ionic & Covalent Bonds
Topic: Sulfate
Replies: 8
Views: 28

Re: Sulfate

Sulfur can have an expanded octet because it has valence electrons in the n=3 shell. This means it can basically utilize the 3d subshell when bonding, allowing it to have more than 8 electrons surrounding it in a Lewis Structure. Keep in mind that this would not work with the elements that don't fil...
Thu Nov 05, 2020 10:31 am
Forum: Octet Exceptions
Topic: Are all octet exceptions more reactive?
Replies: 5
Views: 63

Re: Are all octet exceptions more reactive?

Yeah, that definitely makes sense. I get that this would really only be the case for radicals due to their unpaired valence electrons, while in the other octet exception situations the atoms don't have a lone electron. I also get why the others don't cause as much "damage" as the radicals ...
Wed Nov 04, 2020 12:02 pm
Forum: Octet Exceptions
Topic: Are all octet exceptions more reactive?
Replies: 5
Views: 63

Are all octet exceptions more reactive?

Hey guys, today in lecture Dr. Lavelle explained that radicals are really reactive and unstable because they don't fall under the octet guideline. This made me confused whether this was the case for the other octet exceptions, like incomplete octets and expanded valence. If anyone has any idea wheth...
Tue Nov 03, 2020 9:32 am
Forum: Trends in The Periodic Table
Topic: Electron affinity and Ionization energy
Replies: 7
Views: 60

Re: Electron affinity and Ionization energy

I agree with the last post and would just add that both electron affinity and ionization energy increase as you move right across a period and as you go up in a group. This is because as you go in this general direction, atoms are more reluctant to let go of the electrons they already have. At the s...
Tue Nov 03, 2020 9:24 am
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 4
Views: 34

Re: Drawing Lewis Structures

I totally agree that figuring out the atom with the lowest ionization energy will help determine the best Lewis Structure. In addition, formal charge can also help us find out which arrangement of atoms is best. If you're unsure about which structure is the best, you can find the formal charges of e...
Mon Nov 02, 2020 10:55 am
Forum: Formal Charge and Oxidation Numbers
Topic: Why do we use formal charge?
Replies: 14
Views: 115

Re: Why do we use formal charge?

That makes sense, I didn't realize it was about maximizing the stability of the compound itself. I get now that a negative formal charge would mean the atom wants to get rid of excess electrons, while a positive charge means it wants to gain more. A formal charge of 0 would thus make it more stable....
Mon Nov 02, 2020 9:58 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configurations
Replies: 2
Views: 29

Re: Electron Configurations

I agree with the previous answer and would just like to add that once the 3d subshell is actually filled, it then becomes lower in energy than the 4s one. This is the reason why we usually write 3d before 4s for electron configurations even though on the periodic table itself, 4s comes before 3d. It...
Mon Nov 02, 2020 9:53 am
Forum: Formal Charge and Oxidation Numbers
Topic: Why do we use formal charge?
Replies: 14
Views: 115

Why do we use formal charge?

Hey guys, I just had a question about making Lewis structures. I know that we have to use formal charge in order to distinguish between possible structures of a compound and figure out which is the most probable one. However, I'm kind of confused as to why this is the case. What does formal charge h...
Mon Nov 02, 2020 9:50 am
Forum: Trends in The Periodic Table
Topic: Oxygen vs Nitrogen and Fluorine
Replies: 4
Views: 38

Re: Oxygen vs Nitrogen and Fluorine

Yeah, I definitely agree with the previous post. Oxygen has a paired orbital which is why it manages to get rid of it more readily than nitrogen (which doesn't have any paired orbitals). In addition, the reason oxygen has a lower ionization energy than fluorine is because of the trends of the period...
Thu Oct 29, 2020 2:17 pm
Forum: Ionic & Covalent Bonds
Topic: Is ionic or covalent stronger?
Replies: 31
Views: 369

Re: Is ionic or covalent stronger?

I was also confused about this. I think ionic bonds are stronger, especially as the electronegativity difference between two bonded atoms increases and as the ionic character of the bond increases. Since increased ionic character means the bond is less covalent, it would mean that ionic is stronger....
Wed Oct 28, 2020 9:58 am
Forum: DeBroglie Equation
Topic: When to Use De Broglie
Replies: 16
Views: 127

When to Use De Broglie

Hey guys, I had a question about when to use the De Broglie equation. When you're solving a photoelectric effect problem and the wavelength of an ejected electron is given, do you still have to use the De Broglie equation rather than the E=ch/(wavelength) equation? I think the latter is only for pho...
Tue Oct 27, 2020 9:16 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: atomic spectroscopy vs. molecular spectroscopy
Replies: 2
Views: 29

Re: atomic spectroscopy vs. molecular spectroscopy

I had this same question regarding that part of the outline. However, I think for that topic we just have to understand that molecular spectroscopy is a bit more complicated as a result of multiple electrons, especially compared to the atomic spectroscopy for hydrogen. In multi-electron atoms and mo...
Tue Oct 27, 2020 9:09 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: wavefunctions - midterm
Replies: 3
Views: 54

Re: wavefunctions - midterm

I believe for the midterm, we just have to have an idea about wavefunctions in general and their connection to Schrodinger's Equation. Dr. Lavelle mentioned how it's necessary to see that the orbitals we visualize are wavefunctions that worked when using Schrodinger's Equation to find energy. Thus, ...
Mon Oct 26, 2020 11:07 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Units for Heisenberg Indeterminacy Equation
Replies: 6
Views: 45

Re: Units for Heisenberg Indeterminacy Equation

That definitely makes sense! I always miss the per hour thing too haha. But now I'll definitely make sure that the units are always kg and m/s when doing problems with Heisenberg's Principle. Thank you guys!
Mon Oct 26, 2020 9:59 am
Forum: Balancing Chemical Reactions
Topic: Tips for Complicated Chemical Reactions
Replies: 6
Views: 72

Re: Tips for Complicated Chemical Reactions

I completely agree with the other responses and would like to add that it's important to just focus on balancing one element at a time and not rushing, because it can be really overwhelming to simultaneously focus on balancing multiple at a time. Also, if any element appears on its own (like H2 or O...
Mon Oct 26, 2020 9:52 am
Forum: Photoelectric Effect
Topic: Lyman Series
Replies: 30
Views: 199

Re: Lyman Series

Yeah, we should assume that the final energy state in the Lyman series is n=1. This is because the jump from n=1 to other energy levels requires a lot of energy, specifically from light in the UV region (which is where the Lyman series is found). Since the Balmer series is visible light and thus can...
Mon Oct 26, 2020 9:48 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Units for Heisenberg Indeterminacy Equation
Replies: 6
Views: 45

Units for Heisenberg Indeterminacy Equation

Hey guys, I had a question regarding the units for the Heisenberg Indeterminacy Equation. I know for the De Broglie Equation, we have to make sure mass and velocity are in kg and meters/second (respectively). However, I wanted to make sure that this was also the case for the Heisenberg Principle. So...
Thu Oct 22, 2020 10:53 am
Forum: *Shrodinger Equation
Topic: Schrodinger's Equation
Replies: 5
Views: 85

Re: Schrodinger's Equation

I was a bit confused as well about the relationship between Schrodinger's Equation and the orbitals, but I think in general we just have to be aware that his equation gives us a mathematical model that we use to visualize orbitals. In addition, the variable "E" in Schrodinger's equation gi...
Wed Oct 21, 2020 11:16 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Final vs Initial State
Replies: 4
Views: 40

Re: Final vs Initial State

Yeah, it definitely makes sense to keep track of what you're entering in so that you get an answer that makes sense. I also like to use that other formula because it helps me understand what I'm doing a bit better, and I can clearly see the difference between the initial and final levels. Thank you ...
Wed Oct 21, 2020 9:50 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Final vs Initial State
Replies: 4
Views: 40

Final vs Initial State

Hey guys, I had a question about the equation v = -R(1/n^2 - 1/n^2). I was trying to understand how you would know when using this equation which "n" is the initial state and which is the final state. I know you have to always subtract by doing final energy level minus initial energy level...
Tue Oct 20, 2020 9:07 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Absorption vs Emission Spectrum
Replies: 4
Views: 45

Re: Absorption vs Emission Spectrum

I completely agree with the other answers and would just like to add that an absorption spectrum looks like an electromagnetic spectrum (for visual light as an example) with black lines on the colors. These black lines represent the wavelengths of light that are absorbed by the hydrogen atom, which ...
Mon Oct 19, 2020 1:47 pm
Forum: DeBroglie Equation
Topic: Maximum wavelength?
Replies: 3
Views: 43

Re: Maximum wavelength?

Yeah, the fact that mass will dominate when it comes to the De Broglie equation definitely helped me understand it better. Also I agree, Dr. Lavelle clarified a few of the things that were previously confusing me during lecture today, especially about detectable wavelength. Thank you for the help!
Mon Oct 19, 2020 10:54 am
Forum: DeBroglie Equation
Topic: E=pc and E=pv
Replies: 10
Views: 81

Re: E=pc and E=pv

Since we often refer to the speed of light, which is velocity, we use the letter "c" to specifically reference that value. Thus, in this case, we can use them interchangeably in order to derive the De Broglie wavelength equation. If you write c in place of v, you are saying that velocity i...
Mon Oct 19, 2020 10:01 am
Forum: DeBroglie Equation
Topic: Maximum wavelength?
Replies: 3
Views: 43

Maximum wavelength?

Hey guys, I had a question about the De Broglie equation. I understand that there is a minimum wavelength that makes some objects (that are large) hard to study because their wavelengths are lower than what we can actually observe. However, I was wondering whether there was a maximum wavelength and ...
Mon Oct 19, 2020 9:54 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: How to calculate ΔP and ∆x
Replies: 3
Views: 35

Re: How to calculate ΔP and ∆x

I totally agree with the other answer, I would just like to add that when determining the values for uncertainty of p and x, make sure to look whether there is a +/- symbol in front of the given information. For example, when the problem tells you that the velocity is known up to +/- 3 m/s, then you...
Mon Oct 19, 2020 9:50 am
Forum: DeBroglie Equation
Topic: Wavelike Properties [ENDORSED]
Replies: 9
Views: 147

Re: Wavelike Properties[ENDORSED]

That's true, I didn't think about that; a really big object that's moving really slow might in fact have different traits in the de Broglie wavelength that aren't just how much you notice it. In addition, the kinetic energy perspective you used kind of helped me understand what I was asking to begin...
Fri Oct 16, 2020 9:57 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty of mass?
Replies: 3
Views: 56

Re: Uncertainty of mass?

That definitely makes sense, thank you so much! I also don't think we would have to find the uncertainty for much other than an electron or maybe large objects just to show that their wavelength is too short to study, but I just wanted to make sure. Thanks!
Thu Oct 15, 2020 10:33 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty of mass?
Replies: 3
Views: 56

Uncertainty of mass?

Hey guys, I have a question about the Heisenberg Uncertainty Equation and whether or not you can use it for things other than electrons. Usually, problems ask about electrons and the uncertainty in their position/momentum, which is why the mass is always the same (while the volume is usually uncerta...
Wed Oct 14, 2020 10:02 am
Forum: Properties of Light
Topic: Finding kinetic energy
Replies: 3
Views: 66

Re: Finding kinetic energy

Hey, one thing to make sure is that you're using the right units. The mass of the electron is usually given and it is written in kilograms, but if the velocity isn't written in meters/second then you will have to perform unit conversion to get it into that form. Besides that, one thing that sometime...
Tue Oct 13, 2020 8:24 am
Forum: Photoelectric Effect
Topic: Photoelectric effect post assessment #27
Replies: 3
Views: 31

Re: Photoelectric effect post assessment #27

Hi, yes that would definitely be correct! You have the frequency of a photon, and thus, in order to obtain its energy, you would plug it into the equation E = hv. Once you multiply the given frequency by Planck's constant, you should get the energy per photon. I hope that helps!
Tue Oct 13, 2020 8:20 am
Forum: Properties of Light
Topic: Sapling Textbook 1A.15
Replies: 2
Views: 70

Re: Sapling Textbook 1A.15

Hi, I would definitely agree with the above response and just add that since this is occurring in the ultraviolet spectrum of hydrogen, it's in the Lyman spectrum, which indicates that the hydrogen atom will come down to a ground state of n=1. This helps us understand the values that we get and thus...
Mon Oct 12, 2020 11:42 am
Forum: Quantum Numbers and The H-Atom
Topic: Atomic Spectra Equation [ENDORSED]
Replies: 3
Views: 59

Re: Atomic Spectra Equation[ENDORSED]

Yes, that definitely helps! It makes sense that when you observe this experiment in terms of the emission (rather than absorption) of photons, then the equation would have a negative sign in front of it. Also looking at the equation, it makes sense that as n increases, the energy moves towards 0, so...
Mon Oct 12, 2020 10:06 am
Forum: DeBroglie Equation
Topic: Wavelike Properties [ENDORSED]
Replies: 9
Views: 147

Re: Wavelike Properties[ENDORSED]

I understand that larger mass may make wavelengths less noticeable, but so would a lower velocity. Does that technically mean that wavelengths can be observed in objects with large mass and low velocity? Or, must it be a small mass and high velocity as the professor said? I was also wondering wheth...
Mon Oct 12, 2020 10:00 am
Forum: Properties of Light
Topic: Lyman, Balmer, Paschen, Brackett Series
Replies: 3
Views: 60

Re: Lyman, Balmer, Paschen, Brackett Series

I was also confused when it came to understanding the different series of spectral lines. However, my understanding is that you have to be aware that when an electron returns to ground state in the Lyman series (which occurs in UV light), it returns to the energy level n=1. This will often help in c...
Mon Oct 12, 2020 9:52 am
Forum: Quantum Numbers and The H-Atom
Topic: Atomic Spectra Equation [ENDORSED]
Replies: 3
Views: 59

Atomic Spectra Equation[ENDORSED]

Hey guys, I was wondering if someone could help me understand an aspect of the atomic spectra equation, En = -hR/(n^2). Specifically, the negative sign in front of the equation confuses me a bit. Is it because when an electron lowers from one energy level to another it emits photons (which have ener...
Fri Oct 09, 2020 11:01 am
Forum: Properties of Light
Topic: Speed of Light in Equations
Replies: 6
Views: 26

Re: Speed of Light in Equations

I'm pretty sure that yes, we must assume that it is occurring in a vacuum. When we look at the photoelectric effect, for example, we will also see that the idea of the experiment occurring in a vacuum comes up once again. Thus, even if it isn't explicitly stated, we should assume that it is.
Wed Oct 07, 2020 1:39 pm
Forum: Properties of Light
Topic: Focus 1A Question 11, Series of Light
Replies: 3
Views: 27

Re: Focus 1A Question 11, Series of Light

I researched this a little bit and, from what I can gather, the lines that are grouped together all have the same starting energies. For example, in the Balmer series, electrons always start and return to n=1. Similarly, in the Lyman series, they always start and return to n=1. Hope this helps! Yea...
Wed Oct 07, 2020 12:39 pm
Forum: Properties of Light
Topic: Focus 1A Question 11, Series of Light
Replies: 3
Views: 27

Focus 1A Question 11, Series of Light

Hey guys, I had a question about problem 1A.11 that asks about the spectrum of hydrogen and its line series (like the Balmer series and Lyman series). The problem is the following: In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series (for examp...
Wed Oct 07, 2020 10:00 am
Forum: Molarity, Solutions, Dilutions
Topic: Fundamentals G.25
Replies: 4
Views: 57

Re: Fundamentals G.25

That's the method that I used! I was also a bit confused after doubling the volume so many times and finding the final value. I ended up with 8.1 * 10^-31 moles of x and assumed that this should simply be the answer. However, in the context of the problem, since it asks us to analyze the health bene...
Wed Oct 07, 2020 9:48 am
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 22
Views: 348

Re: Bond Length

I have not learned anything about Angstroms and cannot find a lot about it online. Can someone walk me through how to solve the problem below? All of the organic compounds contain C and H as their essential elements, the bond length of C-H is 110 pm. Express the C-H bond length in Angstrom. Basical...
Tue Oct 06, 2020 10:56 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Self Test E.5B
Replies: 3
Views: 35

Re: Self Test E.5B

I was also confused about whether "formula units" asks for moles or the actual quantity (as in using Avogadro's number). I believe that when the question asks you to find the "amount" of formula units, then it wants you to find moles. However, when the question asks for the "...
Tue Oct 06, 2020 10:50 am
Forum: Significant Figures
Topic: Tips for counting sig figs?
Replies: 9
Views: 86

Re: Tips for counting sig figs?

I agree with the other answers to this question, and would maybe add that it's important to remember that the rules for adding and subtracting sig figs are different than for multiplying or dividing them. When adding and subtracting sig figs, the number with the lowest amount of digits after the dec...
Mon Oct 05, 2020 1:38 pm
Forum: Balancing Chemical Reactions
Topic: Help Balancing this Equation, Problem L.35
Replies: 6
Views: 74

Re: Help Balancing this Equation, Problem L.35

Ohh okay that makes sense, I was also considering that maybe it was an error in the textbook. I kept trying to balance the oxygen atoms and it just wouldn't work. This new formula, meanwhile, seems like it can be balanced. Also, thanks for letting me know that Dr. Lavelle has a page on his website w...
Mon Oct 05, 2020 11:08 am
Forum: Balancing Chemical Reactions
Topic: Help Balancing this Equation, Problem L.35
Replies: 6
Views: 74

Help Balancing this Equation, Problem L.35

Hey guys, I had a question regarding problem 35 from the Fundamentals L section of the book. It reads as the following: Sodium bromide, NaBr, which is used to produce AgBr for use in photographic film, can itself be prepared as follows: Fe + Br2 = FeBr2 FeBr2 + Br2 + Fe3Br8 FeBr2 + Na2CO3 = NaBr + C...