CHEMISTRY COMMUNITY

Brianna Martilla 1C

Hey everyone, we're heading into our last week of the quarter and I want to remind you that you are amazing and should be proud of yourself. Hopefully this quarter went well for yall. What is the one thing you are most proud of that you did/persevered through/completed this past quarter?

Brianna Martilla 1C

I have always done my notes handwritten because I can format them the way I want and I feel like I remember things better that way.

Brianna Martilla 1C

The final review sessions are really helpful; I definitely recommend going!

Brianna Martilla 1C

Wow, I love everyone's responses. This is something I struggle with a lot, especially this quarter for some reason. I find myself procrastinating on simple tasks, so I try to get rid of the pressure to do those tasks by giving me a time limit that is easily attainable. For example, if I have two ass...

Brianna Martilla 1C

Identify the oxidizing and reducing agents in the skeletal (unbalanced) reaction. Then, balance the reaction, including the phase (solid, liquid, etc.) of each species. The reaction takes place in basic aqueous solution. Cl2O7(g)+H2O2(aq)⟶ClO2^-(aq)+O2(g) Can someone explain how to come up with the ...

Brianna Martilla 1C

Love seeing all of your recommendations; I will be sure to look into them. My favorite book is Jurassic Park by Michael Crichton, but more recently I have read An Absolutely Remarkable Thing by Hank Green (and am currently reading the sequel), and The Kite Runner by Khaled Hosseini.

Brianna Martilla 1C

I would say the final is similar to the midterms. My biggest issue was not having enough time, so you can practice going quicker or try doing the easier questions first so that you don't lose those points.

Brianna Martilla 1C

Mine was a different reaction, but similar steps. You have to split into half-reactions, balance out the oxygens with water, then finish balancing out the hydrogens with H+, and finally add as much OH- as you need on each side to change the H+ to water until everything is balanced. Use the feedback ...

Brianna Martilla 1C

Separate this redox reaction into its balanced component half‑reactions. Use the symbol e− for an electron. Cl2+2Cu⟶2CuCl I am having trouble determining the two half-reactions of this. So I think chlorine is the one being oxidized because it is losing electrons because it normally has a -1 charge, ...

Brianna Martilla 1C

I struggle with procrastination and thinking I have more time than I do, so I also have planners to help me set tasks for the day and visualize what the days ahead of me will look like. I have a school planner and a general planner to include everything that I might forget about. I also have trouble...

Brianna Martilla 1C

Good luck to all of you that still have midterms! Make sure to relax afterward and do something fun. I will be watching YouTube or baking cookies.

Brianna Martilla 1C

I think the grading scale is a standard letter scale up until then. However, last quarter I ended up with a grade higher than I expected based on percentage.

Brianna Martilla 1C

Entropy (S) is different than change in entropy ( $\Delta$ S), which is the change in entropy of the system or surroundings or universe. So use the formulas when finding that change.

Brianna Martilla 1C

This was the problem given formulas, delta g values in a table, and was asking to find the K value. I was able to solve it using delta Gr= -RTln(K), but I was wondering if anyone knew why for the second reaction, the K value was so large. I thought I had to be doing something wrong, but I checked my...

Brianna Martilla 1C

So I think I will be taking 14BL in the winter if it's available, but if it's not I want to take a GE. Does anyone have some recommendations for interesting classes? I feel like there are fewer available than I thought. Anyway, I'd love to hear about your experiences!

Brianna Martilla 1C

They each have their own units being used so they are each applicable to their own problems. I had a hard time differentiating the two for a bit until I paid attention to the units.

Brianna Martilla 1C

Happy Valentine's Day to everyone! Any plans?

Brianna Martilla 1C

Calculate the standard molar entropy of vaporization of water at 29.0 °C , given that its standard molar entropy of vaporization at 100.0 °C is 109.0 J⋅K−1⋅mol−1 and the molar heat capacities at constant pressure for liquid water and water vapor are 75.3 J⋅K−1⋅mol−1 and 33.6 J⋅K−1⋅mol−1 , respective...

Brianna Martilla 1C

Thank you all for the help. I was able to solve it using your directions, but why does the feedback say convert Cv to C? Is there another way to solve or am I misinterpreting it?

Brianna Martilla 1C

I'm planning on chem 14BL, math 3c, and ls 7b. But if anyone knows of some interesting ge's I'd love to hear them!

Brianna Martilla 1C

Who do you think will win the Superbowl?

Brianna Martilla 1C

I was having trouble with this problem:

2NaN3(s) $\rightarrow$ 2Na(s) + 3N2(g)

Calculate the value of work for the system if 21.1 g NaN3 reacts completely at 1.00 atm and 22 ∘ C.

I think I'm supposed to use PV=nRT, however I'm not sure how to find the number of moles for N2 to plug in for n.

Brianna Martilla 1C

You divide the original delta H value by number of moles, so 358.8/4. Then you divide the given kJ value by that value to get the number of moles of CS2 there are. Finally, multiply the number of moles by the molar mass of CS2.

Brianna Martilla 1C

Love this question! I have been swimming almost every day!

Brianna Martilla 1C

I don't think he's said anything yet. I would wait for an email or for our TAs to say anything.

Brianna Martilla 1C

Sometimes it's not really possible, but I try to ask myself if my answer makes sense. If my answer seems too high or low, I double-check the little things like decimal places.

Brianna Martilla 1C

Hello! I'm currently taking Chem 14BL right now, and I just want to advise that this class, while not the most difficult material, is a lot of work. So if you think you are already going to have a busy schedule next quarter, you might want to consider whether you can handle this extra workload (wee...

Brianna Martilla 1C

For problems where you need to calculate reaction enthalpies using bond enthalpies, is there a standard table of bond enthalpies? When I look them up, there is a wide range of answers, which would have a big effect on the final answer. Thanks.

Brianna Martilla 1C

Reversible reactions can go both ways while irreversible ones cannot (once reactants form products it is difficult/impossible to reverse). I think you would only know experimentally, for example wood burning would be irreversible, while melting ice is reversible because you can freeze it again.

Brianna Martilla 1C

Thank you everyone for the help. Why is it that you kept the first equation the same? Is it because it was the longest and could be canceled out by the others easiest?

Brianna Martilla 1C

Also, do you think we will all be on one large zoom, or further separated like last quarter in our discussion groups?

Brianna Martilla 1C

I mostly listen to alternative or indie rock music, but recently I have enjoyed punk rock or 2000's pop-rock. If anyone has suggestions I'd love to hear them.

Brianna Martilla 1C

Do you mean on the midterm? If so, there is a section on acid and base equilibria, and the corresponding textbook questions are in the syllabus.

Brianna Martilla 1C

You use the ICE box when being asked to find the equilibrium concentration. I think a good way to approach a problem is to see what you are given and what you already know or can determine, and then see what would apply to solve the question.

Brianna Martilla 1C

Man: Is it a crime to throw sodium chloride in your enemy's eyes?

Judge: Yes, that's assault.

Man: I know it's a salt, but is it a crime?

Brianna Martilla 1C

It only has to do with the coefficients.

Brianna Martilla 1C

Thank you everyone for the discussion on this problem! It helped me a lot. Are there any problems like this in the textbook we can practice?

Brianna Martilla 1C

I love the nostalgia of watching Jurassic Park! However I mostly watch YouTube or shows on Netflix like New Girl.

Brianna Martilla 1C

Make sure you calculated the pH, not pOH.

Brianna Martilla 1C

What do you call an acid with an attitude?

A-mean-oh acid

Brianna Martilla 1C

I'm guessing we will have time to get to unit 3, and I'm also guessing our TAs will send an email about it too.

Brianna Martilla 1C

Also remember to pay attention to the coefficients and use the right amount of significant figures.

Brianna Martilla 1C

Yes and yes, I believe. Water is necessary for the H3O+ and OH- to form, but water is not included when solving the equation because it is in large excess.

Brianna Martilla 1C

I had different initial values, but that answer sounds too high. If I recall it is asking for the total pressure, so you plug your x value into the equilibrium row of the ice table, and add all three values together. (My answer was 0.0910 bars for reference.)

Brianna Martilla 1C

Good question! I normally use the Active topics link under Quick links in the upper lefthand corner to read and respond to more recent posts. To post a question, you create a post and put it within a category. To see how many posts you have per week, you go to Your posts under Quick links, and I cha...

Brianna Martilla 1C

You will need to set up an ice table. For initial SO3, find concentration by doing moles divided by liters, which were given. The .120 moles O2 at equilibrium is in the O2 column and row 'E'. Use the exponents to fill in the 'C' row with x's. Now you can solve for x given the O2 value. Figure out th...

Brianna Martilla 1C

My TA said that we will be approximating 1 bar = 1 atmosphere because they are similar enough when converting between them.

Brianna Martilla 1C

Those additional ones are optional but were helpful to me when I didn't know how to draw molecules, so they can help prepare you for future assigned Sapling problems.

Brianna Martilla 1C

I suggest at least a few times per week, but more if you have time. I guess it just depends on if they work for you too. If you can learn independently, then great. But it's helpful to have an experienced student and others to work with. And before midterms and the final is especially helpful. Also,...

Brianna Martilla 1C

There a lot of resources available for extra help. UA sessions are where you can be given practice problems, whereas office hours are where you would ask for specific problem help. Of course, make sure you are doing the sapling, chemistry community, and textbook problems. To get used to the general ...

Brianna Martilla 1C

pH is determined by -log([H+]), so for part a you just plug in the .025 M for H+ concentration. For part b you take into account the wrong volume flask. You take the -log of 200/250 times the concentration (.025 M). The actual pH should be slightly less acidic.

Brianna Martilla 1C

I love reading all your responses; they gave me some ideas on what to do. I plan on painting and drawing because it was hard to make time for that during school. Anyone have movie recommendations from Hulu or Netflix?

Brianna Martilla 1C

I think I'm going to make flashcards on the main terms and topics because writing them down helps me retain things better. I feel like that requires the least brainpower during a break, because I don't think I will have the motivation to do practice problems.

Brianna Martilla 1C

Based on periodic table trends, an acid is weaker when their bond to H is stronger, because it is harder to give up an H+.

Brianna Martilla 1C

Vivian that is a great suggestion! Yeah I think you have to memorize the strong acids and bases, and the rest will all be weak.

Brianna Martilla 1C

Yes I think so because I remember him saying that the pi bonds don't allow rotation because it connects at the two ends, and rotation would break the bond, so for any double or triple bonds that would happen.

Brianna Martilla 1C

Do not let earning a grade lower than an A discourage you! These tests do not define how much you have learned or are capable of! :) I totally agree! It's too late for me to get an A now considering my past exams, but I've accepted it. I'm still working hard to get a B, even though I wanted to just...

Brianna Martilla 1C

Surprisingly okay. Just focusing on studying for finals and staying optimistic for the time I can finally go to campus.

Brianna Martilla 1C

I found this table to be really useful for studying shapes and angles. https://8dd969e7-a-ff053077-s-sites.googlegroups.com/a/coe.edu/principles-of-structural-chemistry/chemistry-and-climate-change/molecular-shapes/CD%20Spectrum.png?attachauth=ANoY7crF6LZuLn5XS4eaA7LRqj1A37qe5pqikDjjrIUlsarDWzmRkpKP...

Brianna Martilla 1C

Electron affinity is the change in energy when an electron is added and defines how likely that atom is to gain an electron, so the noble gases have full valence shells and don't want any more electrons so they have an affinity of 0. It is true that they can gain electrons in the same shell, but I t...

Brianna Martilla 1C

Each carbon atom would be sp2 because there are three regions of electron density (the two single bonds and the one double bond). You have to count that double bond for the other carbon too. Having a visual makes it much easier to see the regions of electron density for any atom. And this works for ...

Brianna Martilla 1C

Hello, I only use the textbook for practice problems, but those are very helpful. To help understand concepts, I like to watch Youtube videos to hear other people teaching me. I really like The Organic Chemistry Tutor, Professor Dave Explains, and CrashCourse.

Brianna Martilla 1C

Yes, london dispersion forces are always present, but are very weak until they add up when many molecules are present.

Brianna Martilla 1C

The same shape molecule can be polar or nonpolar, so a certain shape is not always one or the other.

Table of molecular shapes being polar or nonpolar:

[url]
https://www.pinterest.com/pin/215117319680930383/[/url]

Brianna Martilla 1C

I would practice drawing them the geometric way with the bolded wedge and dashed wedge, instead of just lines, so that you can keep visualizing each molecule.

Brianna Martilla 1C

Yes, I think all molecular shape bond angles can differ slightly from what is expected based on what atoms are in it. For example, SF4 has a see-saw geometry but has bond angles of 173 degrees and 102 degrees.

Brianna Martilla 1C

I think it can give us a general idea of the shape, but is not always quantitatively accurate, because if the surrounding atoms are not all the same, the bond angles will differ slightly than 'expected'.

Brianna Martilla 1C

Well remember a full valence shell would be 8, so the answer is going to be 8 or less. The way I thought of it was the 3d^3 is the description of the last electrons of the electron configuration, so there must be 3 valence electrons. Another way to think of it is that Mn would normally have 7 valenc...

Brianna Martilla 1C

The ground state electron configuration of Ag is [Kr] 5s^{2}4d^{9} , however its actual configuration based on experimentation is [Kr] 5s^{1}4d^{10} so Ag(+1) would be [Kr] 4d^{10} because you take away one electron to make it a positive charge, which you take away from the s subshell because it is ...

Brianna Martilla 1C

The way I think of it is that the stronger the intermolecular bonds, the more energy is required to break those bonds. Heat is a form of energy that will break those bonds and cause it to change states (liquid to gas phase change). This is why hydrogen bonds between water are so important, because i...

Brianna Martilla 1C

Hey! I'm honestly really struggling, especially with this class. I only took the basic high school chemistry and took calculus instead of physics, so I find this content very confusing and difficult. I have never struggled with a class like this and I feel like it's even worse through online. I fee...

Brianna Martilla 1C

I like step-up sessions because they have prepared problems from the topic you are currently on. Drop-in is more for if you have a specific question like a textbook problem you wanted help on. Each has its advantages depending on what you need.

Brianna Martilla 1C

Because electrons all have a negative charge, they will repel each other. This is also why positively charged protons attract electrons.

Brianna Martilla 1C

I also find it hard to study because of distractions at home, such as my family members, noise, my phone, etc. I try to isolate myself from distractions as best as possible and PLAN what I am going to do and by when. Making a plan is like creating short term goals for the day, and will motivate you ...

Brianna Martilla 1C

So I'll admit I did not do very well on the midterm. I missed some conceptual problems and also made errors in my calculations that led to wrong answers. Congrats to everyone who did do well though! If you also didn't do well, how do you motivate yourself or make yourself feel better? If you did do ...

Brianna Martilla 1C

Silver halides are just an exception to the rules about covalent bonds, that you couldn't figure out on your own without experimentation. So you are correct if you refer to other bonds and their characteristics.

Brianna Martilla 1C

For finding formal charge in general, I found this video really helpful. It has multiple examples and is easy to understand.

https://youtu.be/C2l-76VP8s0

Brianna Martilla 1C

The orbital is the magnetic quantum number ( m_{l} ) whereas the subshell is the angular momentum quantum number (l). Orbital is given in terms from -l...0...l, and describes the pathway of an electron in a certain shell, while subshell is the l value, and is a math function that describes the wave-...

Brianna Martilla 1C

I recall Professor Lavelle saying that there are also g, h, i (and so on) subshells, but we won't need to worry about that, especially in this class.

Brianna Martilla 1C

Remember that when you start writing the electron configurations for d-block metals that the d-block goes before the s-block. So d-block metals will usually have 2 valence electrons because of this. There are some exceptions where there is only 1 valence electron, for example, copper, which is why i...

Brianna Martilla 1C

Yes, you are correct. You fill up the 4s orbital first because it has lower energy and orbitals are filled from lowest to highest energy. Once the d orbital is full, it has more energy now and 4s is no longer the lowest energy, so 3d electrons must be removed first. Essentially 4s is only lower when...

Brianna Martilla 1C

Orbitals are like a math function because it is like a prediction and description for its location in relation to the nucleus. I think of it as a coordinate system where the nucleus is the origin. He doesn't want us to think of it like hotel rooms because the three quantum numbers are not the litera...

Brianna Martilla 1C

You can tell it is excited if the electron configuration has a section that is not 'full'. For example, if you were given 1s^{2}2s^{2}2p^{6}3s^{1}3p^{2} , you may realize that the 3s^{1} is not full, and should be 3s^{2} if it were in its ground state, yet the electron configuration keeps going. Thi...

Brianna Martilla 1C

I loved Gravity Falls as a kid and still do now. Some great shows I've watched recently are New Girl, Sherlock, and Bojack Horseman. I also plan on watching Brooklyn 99.

Brianna Martilla 1C

This looks like the same example Professor Lavelle did in his lecture on October 14. You rearrange E=hv and c=lambda*v to get lambda=(hc)/E. E is given and h and c are constants.

Brianna Martilla 1C

I was also having trouble with this problem but I figured it out. After rearranging the de Broglie equation and E=1/2mv^2, you should get $E=\frac{1}{2}m(\frac{h}{m\cdot lambda})^{2}$ to solve for the energy of the electron.

Brianna Martilla 1C

The E. coli bacterium is about 1.9 μm long. Suppose you want to study it using photons of that wavelength or electrons having that de Broglie wavelength. What is the energy of the electron? I figured out the answer to the first part of the problem, but I'm having trouble with this part. The feedback...

Brianna Martilla 1C

What is the minimum uncertainty in the speed of an electron confined within a lead atom of diameter 350. pm? Model the atom as a one-dimensional box with a length equal to the diameter of the actual atom. I was trying to solve a problem using the equation \bigtriangleup p\bigtriangleup x\geq \frac{h...

Brianna Martilla 1C

I am wondering if sapling is not in the same order for everyone because some of my questions 1-19 do cover material we have not yet learned such as quantum numbers and some questions past 19 cover material that we have learned such as DeBroglie. Is there anyway that a list of the specific questions...

Brianna Martilla 1C

Yes that is correct. Electrons have wavelike properties because they can be diffracted by light, and particle-like properties because they have a mass that can collide with other masses (other particles/electrons). The reason larger objects in classical mechanics do not possess wavelike properties i...

Brianna Martilla 1C

I highly doubt they would ever take away time from the midterm from us. I took a Respondus test for another class and the timer at the top didn't start until I finished taking the pictures and setting up. Also, my TA said if we want we should show up early to the discussion so that we can set up, an...

Brianna Martilla 1C

Use lambda=h/mv. h is a constant and velocity is given to us. To find m, divide the mass of two fluorine molecules by Avogadro's number to get the mass of one particle, then convert that value to kg because h, Planck's constant, is in units of Js, or kg*(m^2)*(s^-2)*s. Lastly, remember to use the co...

Brianna Martilla 1C

I believe the problem will state it is diatomic.

Brianna Martilla 1C

Whenever I am given a problem I always see what is given and what I am being asked to find. We are given the value for energy and we are asked to find the wavelength. We can use E=hc/lambda, rewrite that as lambda=hc/E, then solve for lambda because h and c are constants. Just make sure to convert y...

Brianna Martilla 1C

Hey everyone I have a clarification question. I know that we organize and separate waves by their wavelength, but does the frequency have any effect on what type of wave it is? I understand what each term means and its significance to solving equations, but I was just wondering if frequency has a di...

Brianna Martilla 1C

From what I've noticed Professor Lavelle stresses doing the homework problems which are on the syllabus. When I do the problems, I make sure not to check the textbook answer guide until I am done so that I'm not relying on it subconsciously. Also of course going to the drop-in sessions, office hours...

Brianna Martilla 1C

I have not attended a full one, but instead I like to pop in and listen. They were doing practice problems one at a time, chosen by the UA.

Brianna Martilla 1C

It's a bit late, but someone posted these videos about the Heisenberg Uncertainty Principle. by Mackenzie Van Valkenburgh 3G » Sat Oct 17, 2020 7:25 pm These videos give some background information and explanations of the Heisenberg Uncertainty Principle. I found them helpful, so hopefully someone e...

Brianna Martilla 1C

I think we will be allowed to use the one on his website, but I'm not sure about the conversions. I would just know m to nm because it is common for the quantum questions.

Brianna Martilla 1C

Thank you Mary, I finally got it!

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