CHEMISTRY COMMUNITY

Alexa Pham 1D

Yeah, I also separate the cation and anion of the salt and see how each one would react with water -- whether it will produce H3O+ or OH-. The conjugate bases of strong acids won't react with water though so keep that in mind. Same thing goes for conjugate acids of strong bases. So K 2 SO 3 would be...

Alexa Pham 1D

Coordination number of 6 means that there are 6 areas where the ligands are bonded to the metal cation. Using VSEPR knowledge, octahedral would the geometry for a molecule with 6 bonded regions.

Alexa Pham 1D

In the coordination compound naming (the stuff in the brackets), the metal goes at the end. But if we have a cation or anion outside the coordination sphere, they will go in front or in the back respectively.

Alexa Pham 1D

-ate is used when the coordination compound has an overall negative charge.

Alexa Pham 1D

The formula for en is NH2CH2CH2NH2. We know that it's bidentate because of the lone pairs on the nitrogen ends can both bond with the metal cation. And since we know that there are two (en), then that means there are 4 bonding areas with the metal cation. Now we just need to add the bonding areas wi...

Alexa Pham 1D

The more electronegative an atom is, the more it will have the ability to withdraw electrons and stabilize the compound, making it a stronger acid.

Alexa Pham 1D

Yup, the angle would be 180 degrees. If we think about the structure of trigonal bipyramidal, the lone pairs would be on the equatorial area, leaving the two bonded atoms on the axial positions. That is why it's linear.

Alexa Pham 1D

Lone pairs on the central atom are a good indicator to know that the bond angles are less than 90/120/109.5/120 (depends on what the shape is). The lone pairs will cause electron-electron repulsions with the electrons in the bonds near it and that's what causes the bonds to be less than what you'd t...

Alexa Pham 1D

Yeah, I think it's also a good idea to know those simple oxidation numbers because we might asked to find the oxidation number of the metal ion in the coordination compound as a whole.

Alexa Pham 1D

Chlorido and chloro are the same thing so you're technically correct! It seems like chloro is more commonly used though.

Alexa Pham 1D

Hi, I was wondering if AsF2Cl3 is polar or nonpolar. I was thinking that it's nonpolar but I wanted to make sure if you guys think so too. Thanks!

Alexa Pham 1D

In a chelate, would the ligand that connects to the central ion and forms a ring be considered 1 ligand and not 2 ligands? Also, in the example Dr. Lavelle did in today's lecture using Co+2 and NH2-CH2-CH2-NH2, would NH2-CH2-CH2-NH2 be considered a bidentate?

Alexa Pham 1D

Thank you all for the clarification!

Alexa Pham 1D

Can someone clarify what the difference between electron geometry and molecular geometry? Thanks!

Alexa Pham 1D

Hi there, For the final exam, will we be required to memorize the bond angles of certain molecular geometry? Thanks! I believe that we have to have a good understanding on the molecular geometry of the different molecules. This will help us predict the bond angles rather than memorizing them. Howev...

Alexa Pham 1D

Samin Kabir wrote:How can someone determine the polarity of a molecule through the shape of it's lewis structure?

I think we can determine the polarity of molecule through the molecular shape (not Lewis structure) in addition to understanding the dipoles that are present around the central atom.

Alexa Pham 1D

"Regions of electron density = number of hybrid orbitals" Because the carbon in ethene only has 3 electron densities, then there are 3 sp 2 hybridized orbitals. However, because we need to conserve the amount of orbitals from the original 2s and 2p (that would equal 4 orbitals in total), t...

Alexa Pham 1D

When I think of organic compounds, I think of hydrocarbons. Usually, these molecules/compounds play a role in biological systems and are thus called "organic."

Alexa Pham 1D

Hi everyone, in problem #18 of the Sapling homework for week 7/8, there is a question that's asking about which structures are in the same plane. The compounds are H 2 CCH 2 , H 2 CCCH 2 , and H 2 CCCCH 2 . At first I thought all of them would be in the same plane because all of the structures conta...

Alexa Pham 1D

Hi everyone,
I don't think we went over what T-shaped was in lecture so I was wondering if anyone can explain its shape in terms of electron arrangement, lone pairs, number of bonded atoms, and bond angles. Thanks!

Alexa Pham 1D

What are the bond angles of the seesaw molecular shape? And square planar?

Alexa Pham 1D

In SOCl2, what would the bond angle be for the Cl-S-Cl portion of the structure? It looks linear but because there's a lone pair on the S, is it less than 180 degrees?

Alexa Pham 1D

If you think about it in terms of atomic radius and how atomic radius decreases as you move from left to right of the period, it is observed that the p-orbital atoms are closer to the nucleus. The nuclear charge gets larger from left to right of the period, pulling the electrons more. I'm not quite ...

Alexa Pham 1D

So to sum up, when the question is asking for which compound has the higher melting or boiling point, it is asking for which compound has the stronger intermolecular interactions? I just want to make sure that it's ok to think about melting and boiling point in the same way when it comes to these ty...

Alexa Pham 1D

Following the logic that Na becomes very stable after losing 1 electron as it attains noble gas configuration, can we also say that Na has higher 2nd ionization energy relative to Al? Yes! When an atom has the noble gas configuration, it's a lot harder to remove or add electrons since it's comforta...

Alexa Pham 1D

Does a molecule with an ionic bond have a higher BOILING point than a molecule that has hydrogen bonding? And how would you rank these molecules in order of decreasing boiling point: C3H7OH, N2, C4H8, LiCl?

Alexa Pham 1D

How do we know when two atoms have a coordinate covalent bond and when two atoms don't? For example, if we were to draw a Lewis structure on some molecule that has coordinate covalent bonds, how would we know that there are those coordinate covalent bonds in the molecule?

Alexa Pham 1D

Lewis acids accept electrons and Lewis bases donate electrons. A way that I try to remember it is that Lewis Acids Accept electrons. And then I just remember that the other one donates.

Alexa Pham 1D

Generally, it should be the least electronegative atom in the center.

Alexa Pham 1D

I think generally yes. I've been putting the atom with the least ionization energy or least electronegative in the center since it can make more bonds too.

Yes, the P goes in the center of POCl3.

Hope this helps :)

Alexa Pham 1D

How do you know that there's a triple bond between the carbon atoms in the acetylide ion? I drew the Lewis structure with a single bond between the carbon atoms and it still had the right amount of total electrons. But I guess that's not the correct Lewis structure for this ion.

Alexa Pham 1D

Those were great explanations! I fully understand it now :)

Alexa Pham 1D

I'm still not quite sure how phosphorus is allowed to have an expanded octet. Specifically, what's the deal with the d-orbital for phosphorus? Thanks!

Alexa Pham 1D

Thanks guys! I think I understand. Just to clarify, when draw the Lewis structure for NO3-, we have to make sure that the octet for each atom is filled first? I think was focused on how nitrogen can only make 3 bonds so that's why I couldn't quite understand why N has 4 bonds in the Lewis structure ...

Alexa Pham 1D

Also, I don't know if I should apply this but in high school chemistry, I learned that nitrogen can only have 3 bonds. So why is it that the nitrogen in NO3- has 4 bonds?

Alexa Pham 1D

I'm just a bit confused still because in the image, it looks like nitrogen only has 4 valence electrons when it should have 5?

Alexa Pham 1D

In Dr. Lavelle's lecture, he went over the Lewis structure of NO3-, the nitrate ion. I'm confused to how both of the single bonded oxygens were able to achieve a full octet, since the "-" in NO3- will only allow the molecule to have one more electron. I hope my question makes sense, it's a...

Alexa Pham 1D

Can Lewis structures be used to represent ionic bonding?

Alexa Pham 1D

kg is an SI unit. Also, in de Broglie's equation, Planck's constant (in the numerator) has the units Js. Remember that J is equal to kg m^2 s^-2. We need to cancel the kg out with a kg in the denominator so that we can eventually get the unit m for wavelength.

Alexa Pham 1D

Yes so something that you should know is that in the ultraviolet light spectrum, the final energy level is always n=1. I believe this is the Lyman series. For the visible light spectrum, the final energy level is n=2 (Balmer series). Now you can use E=-hR/n^2 to find the differences in energy level....

Alexa Pham 1D

Susanna Givan 1L wrote:Is c a constant?

Yes, c is a constant for the speed of light (3.0 x 10^8 m/s)

Alexa Pham 1D

Incident light just refers to the light that is hitting the metal (in the photoelectric effect experiment).

Alexa Pham 1D

Z represents the atomic number according to the lecture slides.

Alexa Pham 1D

Yes, I believe that it correct!

Alexa Pham 1D

I just want to make sure my understanding of writing e- configurations is correct.

Do we write scandium e- configuration as [Ar]3d^1 4s^2 and NOT as [Ar]4s^2 3d^1 because shell n=4 has a greater energy than shell n=3?

Thanks!

Alexa Pham 1D

I remember that in one of Dr. Lavelle's past lecture (Week 1, I believe), he went over the SI unit prefixes. For example, G (giga), M (mega), p (pico), etc. Do we have to memorize all these prefixes or only a select few? I'm worried that I won't be able to calculate things correctly on the midterm i...

Alexa Pham 1D

I know that on Dr. Lavelle's chemistry site, there's a link to a sheet of "Constants and Equations" so maybe check that out! However, I'm not entirely sure if we will be using that one or if Dr. Lavelle will email us another one for the midterm.

Alexa Pham 1D

Hi Maddie,
Yeah, Dr. Lavelle spoke about the black body being able to absorb all radiation but I don't think any content more than that would be tested.

Alexa Pham 1D

I was going to ask the same thing too. Thank you for pointing out the mistake, I thought I was misunderstanding what the "change in velocity" was and as a result, was quite confused.

Alexa Pham 1D

I noticed that in the lecture slide, there was E=pc and E=pv. What is the difference between these two equations?

Alexa Pham 1D

I think you mean E=hc/λ , not E=hc/v, so I will explain the difference between E=hv and E=hc/λ . Both equations find the same thing, which is the energy. However, depending on what information is given in the problem, you'd use one over the other. For example, if they asked to find the energy of a p...

Alexa Pham 1D

D is the answer. The unexpected outcome of the photoelectric effect experiment was that increasing light intensity does not mean more electrons will be ejected from the metal. This led scientists to realize that light has properties of particles too! If light only followed the wave model, increasing...

Alexa Pham 1D

Yes, electrons that drop to n=1 describes the Lyman series while electrons that drop to n=2 describes the Balmer series. A drop to n=1 (Lyman series) will emit UV radiation while a drop to n=2 will emit visible light, so that is another way you can distinguish the two.

Alexa Pham 1D

I just realized that I was putting in the wrong value for Planck's constant the whole time :((((
I thought it was 6.26 x 10^-34 but it's actually 6.626 x 10^-34

Alexa Pham 1D

This is a general question regarding the textbook questions I was doing for this section. When I was doing the textbook problems using the formulas we learned in "the quantum world," I would always get an answer that was slightly off from the answer key and I'm confused why I keep getting ...

Alexa Pham 1D

Reactants and reagents are interchangeable terms so there is no difference. Therefore, you don't need to calculate them in a different way.

Alexa Pham 1D

Yes you are correct. It just depends on whether you're looking at the wave model of light or the quantum one. If we look at the wave model of light, then the intensity is the wave's amplitude. If we look at the quantum description of it, then the intensity of light is proportional to the number of p...

Alexa Pham 1D

I think it's usually a value that's given in an equation. Or you could solve for it if they give you the energy of the photon. If that's the case, then you'd have to make the kinetic energy portion equal to 0 in order to find the minimum amount of energy (aka work function) needed to emit an electro...

Alexa Pham 1D

Don't forget to convert GHz to Hz. :)

Alexa Pham 1D

When I compare continuous and quantized, I think of this analogy...
Continuous is like an analog clock, and quantized is like a digital clock.
So basically, quantized refers to having discrete values.

Quantized also refers to individual molecules/atoms.

Alexa Pham 1D

I think you just need to plug the given values into the equation: E (photon) - work function = kinetic energy

And E (photon) is also equal to (Planck's constant x frequency)

Alexa Pham 1D

You would need to find the factor by which you multiply the subscripts of the empirical formula with. This can be found by dividing the molar mass of the molecular formula (usually given in the problem) by the molar mass of the empirical formula! Hope that helps.

Alexa Pham 1D

I usually assume that equations with stoichiometric coefficients are balanced BUT I think it's best to always make sure. I need to get into the habit of doing this too!

Alexa Pham 1D

Yeah, I also agree with the other posts -- I assumed it was a 1:1 ratio. But I'm still curious as to why we should assume that?

Alexa Pham 1D

Hi, I know it's only Week 1 and we're reviewing Fundamentals but I was a bit confused what E = pc meant when watching the "Wave Properties of Electrons and The De Broglie Equation" audio-visual focus module. If someone could explain it to me, I'd really appreciate it!

Alexa Pham 1D

Since empirical formulas give us the relative ratio of atoms in a compound, yes, they are helpful when we want to find molecular formulas of compounds.

Alexa Pham 1D

I think generally yes.

Alexa Pham 1D

Diluting a solution will decrease the molarity -- but not by decreasing moles, rather, by increasing the solvent. The moles stay the same because adding more solvent will not somehow increase or decrease the moles, only the volume. Remember the molarity = moles/volume. Increasing volume will increas...

Alexa Pham 1D

So what I did first was check what the relationship between the molarity before and after if the volume was doubled. 0.10 M (10 mL) = x (20 mL) x = 0.05 Notice that the volume is 0.10 M before doubling the volume. After doubling the volume, you get 0.05 M which is half of the initial molarity. Now t...

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