CHEMISTRY COMMUNITY

NRodgers_1C

I'm not sure when we will see our scores in the grade book, but we are able to pick up our physical tests the 2nd week of Winter quarter according to the final exam information page.

NRodgers_1C

Thank you!!

NRodgers_1C

I am sick and, unfortunately, was unable to attend lecture today. I was wondering if anyone would be willing to upload or send me their notes? Thanks so much, I just don't want to miss our last bit of content before the final.

NRodgers_1C

I find some of the readings to be too long-winded or confusing for me to figure out what I actually need to know and understand it. Personally, watching Youtube videos on the same topic and taking notes along with it is very helpful!

NRodgers_1C

I also recommend printing out the "Marshmallow" practice sheet and familiarizing yourself, if not doing, the problems before the review session. Make sure to get there early! Last time I came a couple minutes before it began, had to sit in the back, and found it kind of hard to see and fol...

NRodgers_1C

Hi, also attaching my notes from Wednesday because they're typed if any of you prefer that. :)

NRodgers_1C

Additionally, strong acid produces more protons in solution than a weak acid and are almost completely ionized in solution.

NRodgers_1C

Strong acids lose H+ easily and have longer, weaker bonds. Also if the resulting anion is stabilized by electron withdrawing atoms which delocalize and stabilize the negative charge, the acid will be stronger.

NRodgers_1C

Don't forget that because pH= -log[H3O+]= -log(1.0x10-7) = -(-7)=7 for a change in 1 pH unit, the [H3O+] changes by a factor of 10.

NRodgers_1C

Here is a slide I found useful:

NRodgers_1C

I know for the final Dr. Lavelle recommended we work through the acid rain examples in textbook. Does anyone which section of the book this is in? I haven't been able to find it.

NRodgers_1C

Does anyone have any good youtube video suggestions for doing problems with acids and bases or writing the names of coordination compounds?

NRodgers_1C

I think as long as you complete both the homework for week 9 and 10 on something we have covered after Test 2, you should be golden, considering both homeworks are due at the same time.

NRodgers_1C

I have a question about what we need to memorize, however. I know we need to memorize VSEPR geometries and angles, but what else are we expected to know? i.e. the chromium and copper electron configuration exceptions, etc.

NRodgers_1C

Not having a strong foundation in chemistry coming into this class (I took chem sophomore year of high school and forgot much of it), I find it most useful to break things down a lot. I start from the very basics and work up. It can be discouraging when a good number of people are just relearning to...

NRodgers_1C

I went to a workshop for the first time right before Test 2 and I found it so helpful! Personally, I think these small groups work much better for me than large group review sessions. However, I'm in the same boat where I feel like there's a lot of content to learn and not enough time for me to figu...

NRodgers_1C

Hi this is a table I found in the book that I found to be very helpful in connecting hybridization and molecular shape together. It's from Topic 2F and I have been using it in conjunction with a table of the VSEPR geometries and bond angles.

NRodgers_1C

I have heard that some people have their Test 2 grades in the gradebook, but haven't heard of anyone getting their test back yet.

NRodgers_1C

Can someone confirm that my reasoning is correct for why "Angle b is expected to be around 109.5°?" I understand why angles a and c are expected to be approximately 120° (because the VSEPR geometry is trigonal planar). So we must assume that the O has 2 pairs of lone pairs (to complete the...

NRodgers_1C

For this problem, I just drew out the Lewis structure then counted the regions of electron density on each central atom (both Carbons and the Nitrogen) to determine the hybrid orbitals. From there, I just used my knowledge of bond angles in relation to the VSEPR geometries and number of bonds to det...

NRodgers_1C

One of the bits of required knowledge for the Quantum World unit is: "With respect to electron transitions that give rise to a UV or visible spectrum: understand the difference between electronic transitions in atomic orbitals (atomic spectroscopy) and electronic transitions in molecular orbita...

NRodgers_1C

Dr. Lavelle said the test will cover all material covered after the midterm up to the first slide shown in class on Monday, Nov. 18th.

NRodgers_1C

Is the reason sulfur can have three double bond an exception to the octet rule? It can expand into its d-orbital?

NRodgers_1C

I used the trends of the periodic table to compare the polarizing power. First, I recognized that Be2+ was the most electronegative and as the most highly charged, had the greatest polarizing power. Then to compare Rb+ and Sr2+, I again compared electronegativity and atomic radius. Rb+ is less elect...

NRodgers_1C

2D.3: "Which of these compounds has bonds that are primarily ionic? (a) BBr3 ; (b) BaBr2 ; (c) BeBr2." I understand why BBr3 is not a good option, but how are we able to establish that "the electronegativity difference is greater between Ba and Br than between Be and Br, making the Ba...

NRodgers_1C

So the recommended problem sets from the syllabus that we've covered for Test 2 it would be 2D, 3F, and 2E?

NRodgers_1C

What did the chemistry teacher say to deter his students from cheating during the test?

"I got my i-on you"

NRodgers_1C

In the syllabus it lists that the topics in the Chemical Bonds unit are: (ionic and covalent bonds; Lewis structures of inorganic, organic, and biological compounds; resonance structures; formal charge; Lewis acids and bases; coordinate covalent bonds; octet rule exceptions; ionic versus covalent bo...

NRodgers_1C

1E.7 Determine whether each of the following electron configurations represents the ground state or an excited state of the atom given.

Is the reason we can conclude that a, b, and c are excited because the orbital diagrams do not follow the typical rules we use for filling?

NRodgers_1C

1.E.5: "Which of the following statements are true for many-electron atoms? If false, explain why. (d) Zeff for an electron in a p-orbital is lower than for an electron in an s-orbital in the same shell." I understand that the answer given is "True", but I'm just trying to clarif...

NRodgers_1C

1.E.1 "Which of the following increase when an electron in a lithium atom undergoes a transition from the 1s-orbital to a 2p-orbital? (a) Energy of the electron. (b) Value of n. (c) Value of l. (d) Radius of the atom. Which answers would be different for a hydrogen atom and in what way would th...

NRodgers_1C

Does anyone know what portion of questions on the midterm will be from each section we've done? i.e. 2 Fundamental-focused questions, 6 Quantum-focused questions, etc.?

NRodgers_1C

I'm working on this problem and noticed we have to convert ounces to kilograms. Do we have to know this conversion or will it be given? If we do, is there an easier way to get there (i.e. ounces to pounds first)?

NRodgers_1C

Will we be given the mass of the proton/neutron on the formula sheet? Or are we expected to know it?

NRodgers_1C

Where does an electron in the s block live?

An eS-state!

NRodgers_1C

I'm stuck on part B and what equation to use. I got the wavelength of the ejected electron from part A to be= 2.0x10^-10 m. With part B asking "How much energy is required to remove the electron from the metal surface?" would we use the equation for the work function, (E= hv) - Φ = E =½ mv...

NRodgers_1C

I'm doing problem 1B.15 part A right now: "The velocity of an electron that is emitted from a metallic surface by a photon is 3.63x10^3 km/s (a) What is the wavelength of the ejected electron?" My initial instinct to use the equation c=λv in the form λ=c/v using the speed of light and the ...

NRodgers_1C

Does anyone know if this unit conversion is given on the formula sheet or must be memorized?

NRodgers_1C

To confirm: the electrons are acting as the particles? Also: Do short wavelengths always have high frequencies and long wavelengths always have low frequencies? Acknowledging the intensity of the light doesn't effect how many electrons are ejected, is it the length of the wavelength (short or long) ...

NRodgers_1C

Here are some frequently used symbols and their meaning: λ= wavelength (Greek letter lambda) c= the speed of light, =3.00x10^8 m/s v= velocity ΔE= Change in energy p= mv (mass x velocity) (gives momentum of a particle) h= Planck’s constant, =6.63x10^-34 J*s R= Rydberg constant, = 3.29x10^15 Hz n= en...

NRodgers_1C

I'm also having trouble with this problem. I found v using the equation v=c/λ and then used that in the equation ΔE= hv. However, from there I got a little lost. I used the equation En= -hR/ n^2 using n=1 to find Ei. I then plugged in ΔE and Ei into ΔE= Ef-EI to get Ef which I set equal to En= -hR/ ...

NRodgers_1C

Working on the next part of the problem I realized my mistake! I was using wavelength (λ) in my equation ΔE= hv instead of frequency (v). (Lol)

NRodgers_1C

1A.9 "A college student recently had a busy day. Each of the student’s activities on that day (reading, getting a dental x-ray, making popcorn in a microwave oven, and acquiring a suntan) involved radiation from a different part of the electromagnetic spectrum. Complete the following table and ...

NRodgers_1C

This how I concluded "C. The extent of the change in the electrical field at a given point decreases" was the correct answer: In the equation ΔE=hv, ΔE (representing the change in energy of a photon) is proportional to its velocity (aka its frequency) by Planck's constant, h=6.626x10^34 J*...

NRodgers_1C

I'm also having trouble seeing how the chemical equation from part a. relates to the equation from part b. I don't understand how to write "the net ionic equation for the reaction."

NRodgers_1C

For some textbook problems, it asks us to "write the formula for nitric acid" or for "lithium sulfide." For the test, do we need to know how to write the formulas for some of the compounds? How would you do this?

NRodgers_1C

E.9 "Epsom salts consist of magnesium sulfate heptahydrate. Write its formula. (a) How many atoms of oxygen are in 5.15 g of Epsom salts? (b) How many formula units of the compound are present in 5.15 g? (c) How many moles of water molecules are in 5.15 g of Epsom salts?" Can someone expla...

NRodgers_1C

Problem: "In a nanotechnology lab you might have the capability to manipulate individual atoms. The atoms on the left are gallium atoms (molar mass 70 g/mol), and those on the right are atoms of astatine (molar mass 210 g/mol). How many astatine atoms would the pan on the right have to contain ...

NRodgers_1C

Has anyone been able to access their E-book purchased through the UCLA store? I know a lot of people are having trouble with their access code not working. Macmillan keeps telling me that UCLA has to resolve the issue and UCLA keeps telling me it's an issue with the publisher. As of now, I'm doing m...

NRodgers_1C

He doesn't post his lecture slides per se, but if you watch the Audio-Visual Focus-Topics, it's basically like watching the lectures again (at least for the first 4 videos). You can see the slides and pause the videos to take notes.

NRodgers_1C

Does anyone know when our 5 posts are "due" on chem community, as in when they are totaled up for the week? Is it Friday before our respective lectures or before midnight, etc.? Thanks.

NRodgers_1C

Hi everyone. I know it's been a while since I've had to do operations using scientific notation, so here is a quick review I put together if anyone else needs it.

NRodgers_1C

*Repost of my answer to a similar question* Most metals when they react with sulfur will produce a metal sulfide (“compounds that contain a metal atom and the sulfide ion”), meaning the typical chemical equation for a metal sulfide would be MS^2- where M= the metal and S^2- = the anion of sulfur. Fi...

NRodgers_1C

Most metals when they react with sulfur will produce a metal sulfide (“compounds that contain a metal atom and the sulfide ion”), meaning the typical chemical equation for a metal sulfide would be MS^2- where M= the metal and S^2- = the anion of sulfur. First, we have to find the unknown molar mass ...

Search found 54 matches