CHEMISTRY COMMUNITY

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Kathryn 3D wrote:Can someone explain 41d - how many atoms in thymine could form a hydrogen bond. The answer is 4 but I only see 2--on either oxygen. Where are the other 2?

The other two come from the two Nitrogens in the structure.

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For #31, would it also be correct to put NO2 in the complex or does it have to be ONO? I would say it has to be ONO, nitrito, because if you write NO2 that can be mistaken with nitro. Which seem similar but are not because the central atom for each differentiates. I think we should specify ONO-, bu...

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Can someone explain 33b? For this question it's crucial to realize that NaOH is a strong base and therefore we know that it completely dissociates. Once we have identified this, we know that 0.55M NaOH will produce 0.55 OH- because it completely dissociates. From here all that is left is plug in th...

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Sydney Takeda 1G wrote:For #31, would it also be correct to put NO2 in the complex or does it have to be ONO?

I would say it has to be ONO, nitrito, because if you write NO2 that can be mistaken with nitro. Which seem similar but are not because the central atom for each differentiates.

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Can someone explain the bond angles in number 18? For number 18, you have to look at the structure with all bonds, atoms, and lone pairs to make it easy to see what is going on. Once you have a structure that includes every thing see what shapes you have for each atom and from the shape determine w...

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Leela_Mohan3L wrote:How do you go about doing #3 in the acid/base section?

Yes, can someone explain how to solve #3 on the second page of worksheet 9 please?

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Kenan Kherallah 1A wrote:Im just wondering why the tail has a -1 charge since for me when I calculated the formal charges of the nitrogens connected to Co I got +1, +1, +1, +1, and 0
Wouldnt that give an overall +4 charge for the tail?

I also have the same confusion can some explain please?

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I understand how to get the formula from this coordination compound name when looking at the answer however I am still confused on a few things. 1) for things that have atoms/molecules outside of brackets, will the charges from the inside and outside always cancel each other out? In other words, wil...

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The easiest way to determine how many ligands are bounded to any central atom is by looking at the Lewis structure, I always do this first. Even if the problem does not ask for it. Another helpful thing is that when a chemical formula has a subscript that usually means that it will be directly bound...

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Andrea pretty much explained it already but to give you an example, we can look at the common reaction of: HCl + H2O --> Cl- + H3O+ and from this we know that HCl is an acid and it produces the Cl- which is its conjugate base, likewise, H2O which is a base turns into H3O+ which is its conjugate acid...

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Disregard my previous post, for some reason it hadn't downloaded all the comments in the thread. I just saw worksheet 9!

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Hi, is there a worksheet for this past weekend? Thank you!

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I understand the argument that sigma bonds are stronger because they have more overlap, but aren't longer bonds weaker because they are more easily broken? aka sigma bonds versus double bonds which are shorter in length as as a result we say they are stronger because they don't break as easily?

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Thank you for the clarification Kassidy! And when determining which has a higher polarizability the size matters more right?

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In determining which molecules have higher polarizing power, what is more significant their charge or their size? For example what is the process we take to determine Rb+ has a higher polarizing power than Sr2+?

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Hi! Although this problem is not asking for the Lewis structure I was wondering what the most stable Lewis structure for ClO2 would be? I got Cl as the central atom with the two O at each side. With two double bonds and 3 e- on the Cl. Is this the most stable structure? The solutions show single bon...

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Oh okay thank you! So the structure that I described above is still one possible structure but it is less stable?

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Hi! Homework problem 3.57b from the 6th edition asks for the Lewis structure of hydrogen sulfite ion and I got a different answer than the one on the answer key. Can someone explain how they got the H attached to O and not S (the central atom)? I got a tetrahedral shape, with S as the central atom a...

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Additionally, a sigma bond is a single bond meaning that two atoms share 2 electrons. While a pi bond is a double bond, however it's important you remember that 1 pi bond also has 1 sigma bond. Now if you look at a triple bond, that has 1 sigma bond and 2 pi bonds. Hope that helps!

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Does anyone know if the different types of bonds will be on test 3? Thanks in advance!

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Other than the VSEPR model, what other concepts will be on Test 3? I thought there was an outline that listed all topics for each quiz but now I can't find it.

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Does anyone know if there are certain atoms that typically get the unpaired electron in a radical molecule?

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Just for clarification when we say radical we can mean both the molecule with the unpaired valence electron OR the single electron as well? The word is used to describe both?

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Hi all!

For this HW problem, why do we have the oxygen in parts a and c have a positive charge of 1 if it is more electronegative than N and C?

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Well in a lot of cases not all of the atoms can have a formal charge of zero. In Lewis structures, I think we want as many atoms to have a formal charge of 0 as possible, but its especially important that the central atom have a formal charge of 0. Additionally there are only a few atoms that can h...

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Are negative formal charges more preferable in terms of stability over positive formal charges?

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Hey so some of the problems from the homework for the Chemical Bonds section asks us to give the chemical formula when we are given the name of a compound. The problems I am referring to are from chapter 3 #25 and 27 (from the 6th edition). I was able to figure out the chemical formula for most of t...

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Question 6b is asking if a Helium atom or a "new" element GarBreadium have longer wavelengths. The answer key says the GarBreadium will have a longer wavelength but isn't it He because it is less heavy, therefore the denominator in de Broglie's equation \lambda =h/m\cdot v be smaller, corr...

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So we are not taking into account the spin of the electrons? I thought that the energy of an electron did not change if the electron had spin up or down. So for a 4p orbital, would we not have: n=4, l=1, m_l=1,0,-1 and m_s = +1/2,-1/2; a total degeneracy of 6?

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Hi,

Is there any way we can get an answer key for the test we do in discussion section so we can work out the problems we got wrong for preparation for midterms and future tests?

Thank you in advance!

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Okay this makes a bit more sense now! So these are the electron configuration for the ions now what if we were ask for the electron configuration of Nickel (Ni)? Would it be [Ar]3d^8 4s ^2?

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The f-block is added right after element number 57, Lanthanum (La).

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Can someone explain the answers to these two question please. (c) is asking for ground state electron configuration for Ga3+ and (d) is asking for Tl3+. Why the electron configuration for the ion Tl3+ is [Xe]4f^14 5d^10? I thought it was [Xe]4f^14 5d^8 6s^2? Same thing with Ga3+, I thought it was [A...

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Yea! It is easier to remove the electrons that are on the outer shell. I think it helps if you start with the electron configuration of Cu first which from lecture we know it is one of the special exceptions as (Cu): [Ar] 3d^104s^1. From there you can see that the electron configuration for the ion ...

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Hi! So this is the one electron configuration that I got right out of all 4 parts. As you might recall from lecture, copper (Cu) is one of the exceptions that Dr. Lavelle talked about. So the electron configuration of just Cu is [Ar]3d^104s^1. However the question is asking for the electron configur...

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So if the radius is given that is the electron's uncertainty in position? Or do we have to multiple it by 2 so it can be the diameter?

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Like everyone already said, the mass of an electron will be given to us. Here is the link to the formula and constant sheet that will be provided to us for tests, midterms, and exams. https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf

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I was wondering the same thing since in a couple of the HW problems it ask in what spectrum a certain wavelength falls into. Thanks for the clarification! I will make sure to know the wavelength for visible, ultraviolet, and infrared. But do we also need to know the frequencies of these?

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Hi! Where do these workshops take place? I would like to attend.

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If we forget to do the 3 post one week, do we automatically loose those 3 points? Does anyone know if there is a way to gain them? Thank you!

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I got it now! The energy of the photon that should be used to solve for wavelength in part c is in fact 2.25 x 10^-17J which is obtained from adding up the energy from part b (1.66 x 10^-17J) to the kinetic energy (1/2mv^2) of the electron. Once you do that you should get 2.25 x 10^-17J which is use...

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I am having the same problem, I am getting 12nm for the wavelength instead of the 8.8nm that the solutions manual says. My answer for part b was 1.66x10^-17J, not 2.25x10^-17J. How did you get 2.25x10^-17J?

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I personally always like to write out the SI units for Joules in order to make sure the units match with everything else and I am not using the wrong variable. However in terms of when you actually NEED to write out the SI units, I would say whenever the question asks you to, otherwise there is no n...

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Hi, so just to clarify the v in the equation E=hv is not velocity but frequency?

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Hey, can someone explain why (2.5x10^16 1/s) is used as the velocity and not the velocity that was given at the beginning of the problem (3.6x10^3 km/s)? Thank you in advance!

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The variable h in this equation, as my classmates have said, is Planck's constant and it's equal to 6.626*10^(-34). It has units of [J*s] which can also be converted to [kg*m^(2)*s^(-1)]. It will be given to us on exams.

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I think when taking values from the period table it's safe to use 4 sig figs.

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Turns out the 6th Edition is on reserve!

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Hi! I have the 5th edition of the textbook but the page numbers are not provided for this version on the syllabus. Is the textbook not available for reserve at the library? Because I came to Powell but they only have the 5th edition textbook too! Can someone please help me ? I have discussion tomorr...

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Alright, thanks again!

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I was wondering where they got the temperature change to be 298K, is this the standard temperature to use if the temperature is not given in the problem?
Thank you.

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