CHEMISTRY COMMUNITY

Norah Gidanian 3D

If you get two positive values it is likely that one of the values was larger than the initial concentration you are given therefore you would omit that one because you cannot end up with a negative concentration.

Norah Gidanian 3D

K is the value when the concentrations have reached equilibrium while Q is a form of the equilibrium constant expect the reaction has not yet reached equilibrium.

Norah Gidanian 3D

I dont think it makes a difference it would just be easier to do kp if you are given partial pressures. But you must make sure that all of your units are the same so if you got partial pressure and molar concentrations you should convert one of them to be the same as the other and then calculate K

Norah Gidanian 3D

I am pretty sure that it is just a constant we are supposed to memorize that was determined experimentally.

Norah Gidanian 3D

https://www.khanacademy.org/science/ap- ... -principle
I found this video really helpful

Norah Gidanian 3D

My resolution is to get more on top of my work and not procrastinate as much

Norah Gidanian 3D

I wasnt sure where to put this question because there is no forum for acid and base equilibrium but one of the textbook questions asks for the ph and gives us the [H3O+]=1.5mol/L so I took the negative log of 1.5 and got -.176 but the answer key says it is .176. Can anyone explain why

Norah Gidanian 3D

Yes it means that the equilibrium lies more to the right. If K is larger than 1 then it lies more to the right and favors the products

Norah Gidanian 3D

Yes you are right the only things we submit are the sapling questions but there will be more in the upcoming weeks I believe he only posted the first one so far. Textbook problems are also assigned as homework but they do not need to be turned in for a grade

Norah Gidanian 3D

Im not sure if the reasoning behind them are the same but Yes it does seem like they follow the same trends

Norah Gidanian 3D

I think it depends on the question but if you have one of the gases in partial pressure and the others in concentration you will need to convert them all to the same type either concentration or pressure.

Norah Gidanian 3D

Does anyone know how to determine the stability of the reactants vs products based on the kc values? and what does it mean

Norah Gidanian 3D

Does anyone know when we will be done learning about chemical equilibrium and moving onto the next section?

Norah Gidanian 3D

is HCl+ NH3 = NH4Cl a neutralization reaction? no because it is not making salt and water? This is still an acid-base reaction right?

Norah Gidanian 3D

Can someone explain why ionic bonds are soluble in water? Is it because the bonds are weaker because the electrons are being pulled to one side so it makes the bond weaker and easier to break apart in water?

Norah Gidanian 3D

The people above said it best but yes we do not need to know which one of the two it would be but I am pretty sure we should know that the heme complex ligand is square planar and that the three most common shapes are tetrahedral square planar and octahedral.

Norah Gidanian 3D

I was confused about this too but I went to a TA and they said that trigonal planar species can be either monodentate or bidentate. I was confused because in class dr. Lavelle did an example of a trigonal planar and said that the other atoms were too far away to bond. Can anyone explain this.

Norah Gidanian 3D

You would have to look at the charge of each of the ligands. Then once you figure that out you look at how many there are and then if there is a net charge on the compound you must use the charge of the ligands to figure out what the charge of the metal should be in order to equal that net charge. I...

Norah Gidanian 3D

Why would CO32- ion be polydentate. On the lewis structure there are two oxygens which have a lone pair but wouldn't the shape being trigonal planar prohibit it from binding to the same cation? I thought that the oxygens would be too far away from one another to bind to the same cation.

Norah Gidanian 3D

This was really helpful thank you! Its so much easier to do the questions when we can actually visualize the shapes!

Norah Gidanian 3D

I hope everyone had a meaningful and restful Thanksgiving break! I know it was much needed after our midterm!

Norah Gidanian 3D

Does anyone know if we will be taking it in breakout rooms like we did for our midterm? How are we planning on zooming and using respondus?

Norah Gidanian 3D

An easy way to remember is that sigma bonds are always single bonds and then pi bonds are when there are double or triple or more bonds. In that case, one of the bonds in the double or triple will be sigma and the other two will be pi bonds

Norah Gidanian 3D

I think it is named differently because that is not part of the coordination compound. The things outside of the brackets are treated and names as they normally would be if you saw them alone.

Norah Gidanian 3D

Does anyone know when they will start studying? I am nervous that its going to be hard studying the old material while still learning new things.

Norah Gidanian 3D

Can someone explain why the answer to naming this compound:
[Co(NH3)3(OH2)3]2 (SO4)3
would be triamminetriaquacobalt(III) sulfate and not bistriamminetriaquacobalt(III) trisulfate

Norah Gidanian 3D

Could someone explain what I did wrong? I know that there are three regions of electron density and one lone pair. Wouldn't the smallest bond angle between the two sets of bonded electrons be less than 109.5? Since there are three regions of electron density the electron density shape would be trig...

Norah Gidanian 3D

Use Lewis structures and the VSEPR model to give the VSEPR formula for each of the following species and predict its shape: b) iodine trichloride Can anyone explain why the lewis structure is the way it is? I thought there had to be 32 valence electrons but when I look at the answer key and count al...

Norah Gidanian 3D

Can anyone explain how you would get the lewis structure of SnCl2? I cant seem to get it right.

Norah Gidanian 3D

Consider the bonding in H2C═CHCHO. (a) Draw the most important Lewis structure. Include all nonzero formal charges. (b) Identify the composition of the bonds and the hybridization of each lone pair—for example, by writing σ (H1s,C2sp2). Can anyone explain how you are supposed to determine the hybrid...

Norah Gidanian 3D

Noting that the bond angle of an sp3 hybridized atom is 109.5° and that of an sp2 hybridized atom is 120°, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased?

Can anyone explain why the answer would be increasing?

Norah Gidanian 3D

for ClF3 why do you make the 2 lone pairs from the equatorial axis and not from the axial. Since there are 5 regions of electron density. Wouldnt making the two atoms on the axial axis the lone pairs cancel the dipoles out?

Norah Gidanian 3D

I believe that B and Al dont need an octet as well.

Norah Gidanian 3D

Yes! I have been thinking about this too. I am always worried about grades but hopefully the grades for this midterm will come out quicker. I hate waiting lol

Norah Gidanian 3D

Yes. You should remember that all molecules will have LDF forces. But the bigger the molecule the more LDF forces it will have making the forces stronger.

Norah Gidanian 3D

I had mine on Wednesday and I thought it went pretty well. There were only a couple questions that I had to think about for a little while before knowing what to do but after applying what we learned I think I did it correctly.

Norah Gidanian 3D

Silver is an exception. You just have to remember that because it can fill up the shell it would want to do that because it will make the molecule more stable. So instead of filling up the s subshell it will fill up the d subshell and then leave one empty in the s subshell.

Norah Gidanian 3D

Yes Molecules that have a higher melting or boiling point means that they have stronger intermolecular forces. If a molecule has hydrogen bonding it will very likely have the highest boiling point because it has very strong intermolecular forces. That is why waters boiling point is so high

Norah Gidanian 3D

Can someone explain why AgF is more soluble in water than AgI? I understand the fact that polarizability plays a role in this and that since I is larger it is more polarizable so AgI has more covalent character. But arent covalent bonds weaker than Ionic bonds so wouldnt have more covalent character...

Norah Gidanian 3D

Can anyone explain what electrostatic potential energy is? I know he explains it in one of his lectures but I am still confused on what it represents. Does it represent the energy of the electron?

Norah Gidanian 3D

How do you see if there is a dipole moment in a molecule? What are you supposed to look at? And does knowing if a molecule has a dipole moment show you if it is polar or non polar?

Norah Gidanian 3D

How can you tell if NH2OH is polar or non polar? Is it because there is a dipole moment and it is arranged asymmetrically? Can someone explain how you have to determine if a molecule is polar or non polar

Norah Gidanian 3D

How come in class today in the lewis structure of BeCl2 Be did not have an octet? I thought that all atoms have to have an octet. And how come this is not an ionic compound because isnt it a bond between a metal and a nonmetal? Do we draw lewis structures for ionic compounds too?

Norah Gidanian 3D

Draw the Lewis structure, including typical contributions to the resonance structure (where appropriate, allow for the possibility of octet expansion, including double bonds in different positions), for (a) periodate ion; (b) hydrogen phosphate ion; (c) chloric acid; (d) arsenate ion. Can anyone exp...

Norah Gidanian 3D

How does a hydrogen bond work because wouldnt that mean that the hydrogen then has 4 electrons on it and doesnt Hydrogen always only have one bond? We said that hydrogens are the exception to the octet rule. So how come it can have more than 2 bonds?

Norah Gidanian 3D

How do we know that Br2 is a liquid and I2 is a solid. I know he explained in class that since I2 has more electrons and is more polarizable it is a solid but why does that make sense. Since solids are not easily distorted in real life, I thought the molecules are really stuff and do not move around...

Norah Gidanian 3D

Can anyone explain what a dipole is? What would be considered a dipole?

Norah Gidanian 3D

Do we just need to memorize which atoms are exceptions or is there a way to tell? Also what are all of the exceptions we should have memorized.

Norah Gidanian 3D

Does anyone know if this class uses a point system or a percentage system to calculate our grades?

Norah Gidanian 3D

I was wondering if there was a faster way to do resonance structures. Maybe through a formula or maybe by looking at the numbers of each atom.

Norah Gidanian 3D

Are electronegativity and electron affinity basically the same thing? From what I have been reading on the two they seem very similar and I am having trouble understanding the difference between them

Norah Gidanian 3D

Just came across this really funny chemistry joke!
Have you heard the one about a chemist who was reading a book about helium?
He just couldn't put it down.
Thought I would share it

Norah Gidanian 3D

You should definitely watch Love island (UK). It is one of my all time favorite shows. It is so funny and entertaining and their accents make it even better.

Norah Gidanian 3D

Anthracene has the formula C14H10. It is similar to benzene but has three six-membered rings that share common C—C bonds, as shown below. Complete the structure by drawing in multiple bonds to satisfy the octet rule at each carbon atom. Resonance structures are possible. Draw as many as you can find...

Norah Gidanian 3D

Can someone explain why the atomic radius decreases as you move across a period? If there are more electrons shouldnt electron-electron repulsion push them farther away, making the radius larger?

Norah Gidanian 3D

Give the number of valence electrons (including d electrons) for each of the following elements: (a) Sb
Can someone explain why the answer is 5? I thought it was 15 because it says including d electrons. I got the electron configuration to be [Kr] 5s2 4d10 5p3. Doesnt that add up to 15?

Norah Gidanian 3D

Can anyone explain how you would know how to arrange these atoms and ions according to radius: Rb+ Rb and Rb-

Norah Gidanian 3D

If I had copper electron configuration and wanted to make copper 2+ where would the electrons come out of? Would one come out of the 4s and then the other from the 3d?

Norah Gidanian 3D

[Xe] 4f14 5d10 6s2 6p2- this is the electron configuration for lead

Can anyone explain where the 4f14 came from. I thought that was accounted for in the electron configuration for Xe.

Norah Gidanian 3D

Can you have an atomic radius for one atom that is not interacting with any other atoms? Like for example would there be an atomic radius for Chlorine?

Norah Gidanian 3D

Can anyone explain why there is a 4s2 in the examples he was doing like Chromium and Vanadium. I understand where the 3d electron part is coming but why is there a 4s2?

Norah Gidanian 3D

Does anyone know how many questions will be on the midterm?

Norah Gidanian 3D

Copper(II) nitrate reacts with sodium hydroxide to produce a precipitate of light blue copper(II) hydroxide. (a) Write the net ionic equation for the reaction. (b) Calculate the maximum mass of copper(II) hydroxide that can be formed when 2.00 g of sodium hydroxide is added to 80.0 mL of 0.500 M Cu(...

Norah Gidanian 3D

Hi, I was wondering if we can go back and forth between questions on the midterm. I was under the impression that we could not and I dont think I was able to during my practice test but some other students said that we could go to previous questions and see the future ones. Does anyone know for a fa...

Norah Gidanian 3D

Can someone explain what the wave-function represents. Im still a little confused on what it is exactly.

Norah Gidanian 3D

The average speed of a diatomic fluorine molecule at 25 ∘C is 442.4 m⋅s−1 . What is the average wavelength of a fluorine molecule at this temperature? Assume that the molecule acts as a single particle. Can someone walk me through doing this? I keep trying to do it and am not getting the correct ans...

Norah Gidanian 3D

How many orbitals can have the following quantum numbers in an atom: (a) n = 2, l = 1; (b) n = 4, l = 2, ml = 22; (c) n = 2; (d) n = 3, l = 2, ml = 11?

How would you do part c without being given the value of l?

Norah Gidanian 3D

Hi,

I found a really helpful video explaining the four quantum numbers!

https://www.youtube.com/watch?v=KrXE_Sz ... e=youtu.be

Norah Gidanian 3D

Hi,
I was wondering if we needed to buy a webcam/ if anyone did already or if we can use our phones.

Norah Gidanian 3D

It is using this value called h bar where there is a bar on the line of the h. When you substitute h bar into the equation you will get h/4pi.

Hope this helps

Norah Gidanian 3D

All of these replies are really helpful! I think that an electron is ejected once it is really far away from the nucleus that it doesn't have a pull towards it. When an electron is excited, it still has some pull towards the nucleus and will come back down.

Norah Gidanian 3D

Hi
The work function and threshold energy I believe are the same thing. It is just the minimum amount of energy required to remove an electron.

Norah Gidanian 3D

Hi! I believe that all objects have wavelike properties but they are only noticed for very very small objects.
Hope this helps

Norah Gidanian 3D

Hi, I watch all the lectures during the specified time and have been watching the four modules for each unit before we begin the unit so I am prepared and know what to expect for class. I also do the textbook notes as we go through the lectures. I am probably going to re-do all the textbook and sapl...

Norah Gidanian 3D

For the first worked example we did in class today (10/16/20) could we also use the equation v=-R(1/n^2-1/n^2)? I know there is a specific equation we use for the hydrogen atom but would the other equation I just stated work as well?

Norah Gidanian 3D

The question gives you the information that: Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1 and asks you to find the kinetic energy of the ejected electron. I am not sure how to go about doing this, but ...

Norah Gidanian 3D

the wording is a little bit confusing but he is basically stating that if the energy of the photon is larger than the energy required to remove the electron, then the electron will move. If you read it slowly and emphasize the word unless it makes it more clear. He is saying that only when the energ...

Norah Gidanian 3D

In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series (for example, Balmer series or Lyman series, as shown in Fig. 1A.10). What is common to the lines within a series that makes grouping them together logical? Can someone explain this? I cant s...

Norah Gidanian 3D

Hi! So for this question you are probably having trouble balancing because there is a typo in the problem. On Dr. Lavelles website there is a link that says that for question L.35 "In the third reaction step the compound "FeBr2" needs to be "Fe3Br8"" Hope this clears th...

Norah Gidanian 3D

To do this problem I actually used a different formula. I used v=R(1/(n1)^2 - 1/(n2)^2) where R is Rydberg's constant = 3.29 * 10^15 Hz. Using the given frequency I plugged each number into the given formula (v=1.14*10^14 Hz, and n1=4). From there I solved for n2 and ended up getting an energy leve...

Norah Gidanian 3D

To do this problem I actually used a different formula. I used v=R(1/(n1)^2 - 1/(n2)^2) where R is Rydberg's constant = 3.29 * 10^15 Hz. Using the given frequency I plugged each number into the given formula (v=1.14*10^14 Hz, and n1=4). From there I solved for n2 and ended up getting an energy leve...

Norah Gidanian 3D

An excited hydrogen atom emits light with a frequency of 1.14 x 1014 Hz to reach the energy level n = 4. In what principle quantum level did the electron begin? Can someone walk me through how to do this? I used the deltaE formula to get E4-Ex. I used E=hv to get the energy emitted because they gave...

Norah Gidanian 3D

The meter was defined in 1963 as 1,650,763.73 wavelengths of radiation emitted by krypton-86 (it has since been redefined). What is the wavelength of this krypton-86 radiation? To what region of the electromagnetic spectrum does this wavelength correspond (i.e. infrared, ultraviolet, x-ray, etc.)? W...

Norah Gidanian 3D

Concentrated hydrochloric acid is 37.50% HCl by mass and has a density of 1.205 g/m^3. What volume (in milliliters) of concentrated hydrochloric acid must be used to prepare 10.0 L of 0.7436 m HCl(aq)? Does someone mind walking through the steps necessary in order to complete this problem. We did it...

Norah Gidanian 3D

A reaction vessel contains 5.77 g of white phosphorus and 5.77 g of oxygen. The first reaction to take place is the formation of phosphorus(III) oxide, P4O6: P4(s) 1 3 O2(g) S P4O6(s). If enough oxygen is present, the oxygen can react further with this oxide to produce phosphorus(V) oxide, P4O10: P4...

Norah Gidanian 3D

Hi, I am confused on how to approach this question: A 1.50-g sample of metallic tin was placed in a 26.45-g crucible and heated until all the tin had reacted with the oxygen in air to form an oxide. The crucible and product together were found to weigh 28.35 g. (a) What is the empirical formula of t...

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