CHEMISTRY COMMUNITY

Ashley Kim 3H

Your final reaction isn't properly balanced. There should be 3HNO3, 3NO2, and 3H2O

Ashley Kim 3H

Yes, liquids and solids are always ignored in equilibrium calculations

Ashley Kim 3H

qrev refers to the amount of heat that is produced in a reversible process!

Ashley Kim 3H

Yes it is possible, but it would take an insane amount of time

Ashley Kim 3H

I believe that the points are capped at 50!

Ashley Kim 3H

I'm currently taking a cluster so not sure about which GEs are good, but I do know for sure that the Scand and Classics classes are popular

Ashley Kim 3H

I try to run a few miles during the weekend! I love blasting music and forgetting about the work I have by exercising

Ashley Kim 3H

I always take naps after all my midterms. Post-midterm/final naps are the best

Ashley Kim 3H

I think we should be knowing the general oxidation rules, which are helpful when solving problems

Ashley Kim 3H

n in the equation ∆G = -nFE is the number of electrons that are being transferred, which you can find by balancing the half-reactions

Ashley Kim 3H

You have to remove the parentheses for the hydrate! Although I'm not so sure why myself either...

Ashley Kim 3H

I also found it very surprising that most of the midterm was conceptual questions. I will be definitely studying more of those concepts for the final.

Ashley Kim 3H

Work is positive when work is being done on a system, whereas work is negative when a system is doing work.

Ashley Kim 3H

I think for Hess's Law there is some trial and error you have to do when solving a problem. I think I always try to cancel things out in a way so that the products will end up in the products side and reactants will end up in the reactants side.

Ashley Kim 3H

I plan to take 14C during spring quarter and 14BL during summer. While it's useful to have it in person, I heard 14BL is easier online so I'm gonna take it before fall 2021.

Ashley Kim 3H

DeltaE and DeltaU can be used interchangeably!

Ashley Kim 3H

Cis isomers have similar groups placed on the same side of a double bond. Trans isomers have similar groups placed on opposite sides of a double bond.

Ashley Kim 3H

There are different equations involving entropy and you use them based on what the question asks for. Entropy is a measure of how much the energy of atoms and molecules become more spread out.

Ashley Kim 3H

The difference between an isolated and closed system is that a closed system can still exchange energy with its surroundings. An isolated system cannot exchange matter or energy with its surroundings. An example of an isolated system is a thermos or cooler, while an example of a closed system could ...

Ashley Kim 3H

You can tell if the ideal gas is monoatomic, linear molecule or a nonlinear molecule by drawing out its lewis structure. That way, you can determine its 3D structure.

Ashley Kim 3H

Yes, they do matter! Two compounds would have to be the same phase to "cancel out" when using Hess's law.

Ashley Kim 3H

Just as others have states, delta T is for a large overall change in temperature, while dT is for infinitely small changes in temperature.

Ashley Kim 3H

I think the textbook questions and UA worksheets are both extremely helpful. The midterm questions have been very similar to both problem sets. I didn't really attend review sessions but I still did all the worksheets I could find. Sapling is also definitely helpful because it provides a step by ste...

Ashley Kim 3H

The first thing I did was I changed the mass of the ice cub into kilojoules. You can do this by using the molar mass of water to find the amount of moles of ice, and then multiply it by the heat of fusion of water. This amount of energy is the heat required to melt ice. After you get this amount of ...

Ashley Kim 3H

I think that as long as you have 50 posts by the end of this quarter you will be fine. Any other score you have right now will be updated in the future!

Ashley Kim 3H

Start-Up is a popular kdrama that had its final episode not too long ago. My favorite kdramas of all time are She Was Pretty, Strong Woman Do Bong Soon, While You Were Sleeping, and Kill Me Heal Me! I especially loved Kill Me Heal Me.

Ashley Kim 3H

Yeah, I think the test went as I expected. The structure was pretty much the same for Chem14A so there was nothing too surprising. I'm really glad that the problems were similar to the textbook ones because doing all of those really helped me. Reviewing sapling also helped me understand the content.

Ashley Kim 3H

They should be coming out sometime tonight. Good luck everybody, we all did our best :)

Ashley Kim 3H

Yes, thank you Dr. Lavelle for being so accommodating to the digital setting and giving extensions when needed!

Ashley Kim 3H

They should be coming out sometime this evening :)

Ashley Kim 3H

I'm planning on taking it for session A, which already has a designated professor. Session C does not seem to have one yet!

Ashley Kim 3H

Work is the energy transferred by the system to its surroundings, and its equation is W=-PΔV

Ashley Kim 3H

HClO3 is considered a strong acid. So is HClO4 :)

Ashley Kim 3H

Kelvin and Celsius are two different units of temperature. The equation to calculate either one is kelvin = celsius + 273.15

Ashley Kim 3H

If in the expression (x)/(initial concentration) x 100 is less than 5%, you can ignore the x value!

Ashley Kim 3H

Percent ionization is the percentage of the compound that has been ionized or dissociated.

Ashley Kim 3H

Heat is required if a substance goes from liquid to gas. In the phase change diagram, the process of liquid to gas, or fusion, has the same temperature over time because the bonds need to be broken.

Ashley Kim 3H

For an acid, when pH>pKa, the charged species is dominant. On the other hand, if pH<pKa, the neutral species is dominant. Hope this helps!

Ashley Kim 3H

Yes, I believe that that is correct!

Ashley Kim 3H

When bonds are being broken, energy is required. On the other hand, energy is released when bonds are formed.

Ashley Kim 3H

When I study, I listen to lofi and there a ton of playlists on YouTube. These days I've been listening to a lot of j-pop like Yoasobi because it's super catchy. I also listen to a lot of k-indie and kr&b :)

Ashley Kim 3H

The first thing you would have to do is setting up an ICE chart with HA <-> H+ + A-. With the given initial concentration of the acid, you would create an expression and have to solve for x in a quadratic equation. Once you get x, which is the concentration of H+ ions, you can solve for pH by taking...

Ashley Kim 3H

Percent ionization is the percentage of the compound that has been ionized or dissociated. Percent protonation refers specifically to the percentage of hydronium ions that was dissociated.

Ashley Kim 3H

I don't think there are any other pure liquids we should be memorizing, but if there are, they would be notated as a (l) in the chemical equation.

Ashley Kim 3H

You would pick the solution that is less than the initial concentration when using quadratic equations.

Ashley Kim 3H

In this problem, you can solve for Kb because Ka is given since Kb = Kw/Ka. After you get the value of Kb, you would set up an ICE chart to make an equation for Kb. In this case, it would be Kb = [HOCl][OH-]/[OCl-]. Since HOCl and OH- would be regarded as "x" by using the ICE chart, you ca...

Ashley Kim 3H

For this problem, you set up the equation for Q, which is ([NH3]^2) / ([H2]^3 * [N2]) as mentioned above. You would then plug in the given concentrations for each reactant/product and get a value for Q. After compared the value of Q to K, you would see that K>Q, which means that more products are fo...

Ashley Kim 3H

My favorite comfort movies include the Studio Ghibli films or old Disney movies for nostalgia :)

Ashley Kim 3H

For sapling, you can get the free trial, but even then it's due on Week 2 so you don't need to worry too much about it. There's also an online PDF available for the textbook so you can access it without Sapling.

Ashley Kim 3H

A pure substance is anything thats a pure liquid or a solid. For a liquid, this means that they are not aqueous and are usually notated with a (l) in a reaction. Ultimately, a pure substance does not affect the concentration in a reaction.

Ashley Kim 3H

The first sapling HW is due on Week 2 :)

Ashley Kim 3H

I would definitely do all the textbook problems and going to as many UA sessions as you can. If you can't make them, try to find the worksheets they make. All of those worksheets and the textbook have problems that are very similar to the ones on the midterms and final. Also, stay on top of your poi...

Ashley Kim 3H

There's a list of strong acids and bases you can find online and I think we have to memorize them. Anything not on that list would be considered weak. There's also a list from sapling if it helps: https://sites.google.com/site/chempendi ... cids-bases

Ashley Kim 3H

Acids cannot have a negative pH; the pH scale ranges from 0-14.

Ashley Kim 3H

Generally, a strong base has OH- ions and a strong acid has H+ ions. A strong base also has a higher pH while a strong acid has a lower pH. Thus, in this problem we are essentially ordering the molecules from most basic to most acidic. Ca(OH2) is a stronger base than RbOH because it contains one mor...

Ashley Kim 3H

H2CO3 is a stronger acid because C is more electronegative than Ge. We can see the electronegative trend with a periodic table; up a column is more electronegative. As others mentioned, because C is more electronegative, it would be easier for the H+ ions to dissociate in water and is thus a stronge...

Ashley Kim 3H

Ligands are simply ordered in alphabetical order!

Ashley Kim 3H

This problem is essentially combining concepts we learned from the last midterm. In this problem, we can find the compound's molecular formula by using the mass percentage composition. By finding the molecular formula, you can draw its lewis structure.

Ashley Kim 3H

I've been watching a lot of anime over quarantine and I'm currently watching Hunter x Hunter! I also loved Stranger Things, The End of the F***ing World, Erased, ATLA, and On My Block.

Ashley Kim 3H

Yes, bent and angular mean the same regarding the lone pairs that result in its shape.

Ashley Kim 3H

Not sure if it will be more heavily based on the topics towards the end of the quarter, but we should be familiar with all content from the entire quarter because it is cumulative. The format should all be MC though.

Ashley Kim 3H

We can determine the number of sigma and pi bonds depends on what type of bond it is (single, double, or triple). As we know, triple bonds are stronger than double, which are stronger than single.

Ashley Kim 3H

Hi, you don't necessarily have to do 5 posts each week but it's a good idea to so you can keep track of the amount of posts you have. To answer your question, you should just make sure you have 40 by the end of this week!

Ashley Kim 3H

The subshell f starts on the 4th level (4f) but is only seen in 6th period elements. The fact that they have different quantum numbers may be a little confusing!

Ashley Kim 3H

A water molecule is not linear but bent. This bent structure explains why the two lone pair electrons would be next to each other rather than on opposite ends. The lone pair electrons in the water molecule are most stable when next to each other.

Ashley Kim 3H

Yes, valence shell configuration includes both ground state and excited state configuration.

Ashley Kim 3H

Both CH4 and CCl4 are single bonds. But the reason why CCl4 has a higher boiling point is because it has more electron shells. This makes the polarizability increase, thus increasing the strength of LDFs, which then increases the boiling point.

Ashley Kim 3H

Yes I believe that is correct but I doubt we would have to know that for our midterm!

Ashley Kim 3H

For the last midterm I definitely benefitted a lot from doing a ton of problems. I tried to do all the UA worksheets and textbook problems and looked over sapling again. I honestly found the textbook problems to be the most helpful for the test.

Ashley Kim 3H

I saw a post that explained that we can't expect it to be exactly the same with the asynchronous format, but it's most likely so.

Ashley Kim 3H

No, I believe today's lecture content is not on the midterm since it was on the VSEPR model which isn't part of our syllabus for the upcoming test.

Ashley Kim 3H

For this problem, you have to determine which elements in the urea molecule that the water would form hydrogen bonds with. Hydrogen bonds are formed with the elements F, O, and N. You can use this information to find how many hydrogen bonds a urea molecule can have, thus giving us the amount of wate...

Ashley Kim 3H

Are you referring to electronegativity trends in general? Because if so, the electronegativity trend happens to be that across a period is more electronegative, and up a group is more electronegative.

Ashley Kim 3H

There are three oxygen atoms surrounding the central carbon atom, and two of the oxygen atoms have a single bond while the other has a double bond. The oxygen atoms with a single bond have a negative charge, and this is because of formal charge.

Ashley Kim 3H

Just like the answer above mentioned, we would have to observe the molecule's solubility to determine if it has ionic or covalent properties. Other than that, I'm pretty sure any problem we are given related to this would be more specific and not involve an ambiguous value between 1.5 and 2.

Ashley Kim 3H

Hi, I don't think we actually have to draw the double bonds shorter than single bonds for accuracy. I think we should just be able to know that single bonds are longer than double bonds, which are longer than triple bonds.

Ashley Kim 3H

I always listen to some good music before test anxiety so I feel more confident going into the test! When I'm actually taking the test, I make sure to read each question super carefully because they can get tricky. After I look at the answer choices, I always use process of elimination to determine ...

Ashley Kim 3H

I love that principle too, it's really helpful with figuring out electron configurations. Thank you for sharing!

Ashley Kim 3H

Hi, because they gave that the bond length for the perchlorate ion is 144pm for all four bonds which is close to the double bond between Cl and O, we can determine that the bonds in the ion are probably all double bonds. Because the resonance structures C and D have mostly double bonds, I inferred t...

Ashley Kim 3H

This is because of the Aufbau principle, which means that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. In general, 4s is filled before 3d because it is lower in energy. However, there are two exception to this rule which is with a half full 3d ...

Ashley Kim 3H

Yes, I believe that in this question you just assume that PCl3 is the limiting reactant and you can only use that value to solve for the mass of HCl.

Ashley Kim 3H

Hi! For this question, you would first use DeBroglie's equation ( v = h/m*lambda) to find the velocity of the electron with the given wavelength and the mass of an electron (9.11 x 10^-31kg). After finding the velocity, you can plug the value into the kinetic energy equation 1/2mv^2.

Ashley Kim 3H

Since this problem is dealing with uncertainties, you would just ignore the value 8x10^6 m/s and use Δv= 0.01x10^6m/s instead.

Ashley Kim 3H

For the s,p,d,f orbitals, electrons will generally fill up the lower energy orbitals first. This is why 4s is filled up first before the 3d because the 4s orbital is lower in energy. This is known as the Aufbau principle, which means that electrons fill atomic orbitals of the lowest available energy...

Ashley Kim 3H

Yeah I'm pretty sure the test policies for the midterm would depend on your TA !

Ashley Kim 3H

Hi, to find the energy of the electron, the problem gives a hint that the electron's energy is a function of mass and velocity. So to find the energy, you need to first find the velocity of the electron using DeBroglie's equation (v=h/m*lambda). After you find the velocity, you plug that into the ki...

Ashley Kim 3H

Hi, one mistake that often happens is switching up 3 and 2. I don't know if this is the case, but make sure that 2 is N1 and 3 is N2 in the Rydberg equation! After you plug those numbers in and get the frequency, you can use the equation lambda = c/v to get the wavelength.

Ashley Kim 3H

In the Rydberg formula, N1 means the final energy level and N2 means the initial early level. Since in this case 5 is N2 and 2 is N1, this means that the electron travelled from energy level 5 to energy level 2. The electron is not getting excited, but rather emitting energy.

Ashley Kim 3H

As others mentioned, I think it's a good idea to know what energy level transitions each series fall under but I don't think we need to know about them in too much detail!

Ashley Kim 3H

"What is the minimum uncertainty in the speed of an electron confined to within a lead atom of diameter 350. pm? How would you model the atom as a one-dimensional box with a length equal to the diameter of the actual atom?" I'm using the equation [(Mass of the electron)(delta v)](delta x)=...

Ashley Kim 3H

Thank you so much for your explanation! I also realized that I solved it wrong. I realized that I should just use the ΔE(k)=1/2m(Δv)^2 formula for the first part of the question, and I would multiply that answer by avogadro's number for the second part since it's asking for "per mole of hydroge...

Ashley Kim 3H

I'm pretty sure we won't be expected to know the specific wavelengths for each color, but as mentioned above, knowing the ranges would be a good idea.

Ashley Kim 3H

When the peak interacts with another trough, they essentially "cancel each other out" and would result in a smaller wave. On the other hand, if a peak interacts with another peak, the amplitudes are added together and become bigger.

Ashley Kim 3H

The answer for this would be D! Heisenberg's principle doesn't really apply to large objects so uncertainties aren't measurable.

Ashley Kim 3H

Hi everybody! I'm struggling a bit with number 20 for the Heisenberg uncertainty principle post-module questions. 20. Use the above uncertainty in velocity to calculate the electron's uncertainty in kinetic energy. Then calculate the uncertainty in kinetic energy per mole of electrons (that is, per ...

Ashley Kim 3H

Yes I believe so, because the extra m in mmol and mL would cancel each other out since they're both measured in "milli".

Ashley Kim 3H

I think that while the definitions of reagent and reactant are different, the terms limiting reactant and limiting reagent are the same and can be used interchangeably as mentioned earlier. It can also be called a limiting agent.

Ashley Kim 3H

We use 100g because it makes it easier to imagine the sample mass. Since we already found the mass compositions of each element, we can just use those percentages and treat them as if they were grams. By converting them to grams we can then convert to moles to find the empirical formula.

Ashley Kim 3H

Yes, you can always assume that O2 is one of the reactants. A combustion reaction involves a hydrocarbon (molecule with just carbons and hydrogens) and O2 as the reactants and with H2O and CO2 as the products.

Ashley Kim 3H

Yup, there are always problems that don't provide a balanced equation. It's always a good idea to double check!

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