CHEMISTRY COMMUNITY

Jingyao Chen 4H

I know that for ethylenediamine it’s (en). On the review worksheet (Q29) there’s also an abbreviation of (ox). Does anyone have a complete list of ligands that have abbreviations that we need to know for the final?

Jingyao Chen 4H

For 21, how do we know oxidation number of Fe?

Jingyao Chen 4H

I just finished the last class of chem 14A Fall 2019 and just wanted to say thank you Dr. Lavelle for the past quarter!

Jingyao Chen 4H

For #17, what does it mean by the “hybridization of each lone pair”? Is it supposed to be the hybridization of each central atom?

Jingyao Chen 4H

For number 41(c), it asks which pair of atoms on thymine are most tightly bounded and why, between C=C, C=O, and C=N. However, O don’t see a C=N bond in the structure. Is there a mistake?

Jingyao Chen 4H

Is there a way to see past exams/finals problems for this class? Do they have it in the library? I hope to find questions that are similar to the actual final in order to prepare for my final this quarter.

Jingyao Chen 4H

Since the midterm was relatively difficult, is there any resources that we can get to get to practice difficult problems for the final exam? Like I understand the homework problems and the lecture knows, but is there a way to try difficult problems that are similar to the difficulty of the midterm, ...

Jingyao Chen 4H

I know that the final exam will be cumulative. However, does anyone know if the majority of the content will be focused on the things after the midterm, or will it be evenly spread out?

Jingyao Chen 4H

Does anyone have any recommendation as to studying for the final exam? Has any one heard any good advices from previous students?

Jingyao Chen 4H

It is cumulative, and make sure you review problems that you’ve missed on previous exams.

Jingyao Chen 4H

No. There will not be hybridization on test 2. But I still recommend studying it early since it will eventually be on the final :)

Jingyao Chen 4H

An easy way to consider it is just another electron density region. For four, it's sp3. If there's one more, it moves on to the d orbitals.

Jingyao Chen 4H

Adding on, the overlap means the overlap in the possible regions that electrons will be there. Therefore, the greater the over lap, the more electrons there are for sharing/interacting, resulting in a strong bond.

Jingyao Chen 4H

Yes, lone pairs are counted. The thing that "doesn't count" is a double bond. It "doesn't count" in terms of it is considered the same as a single bond.

Jingyao Chen 4H

The purpose of hybridization is to result in an overall lower energy level. Therefore, I think as long as there's bonds that involves the p orbital, there will be hybridization between s and p to form an energy level in between.

Jingyao Chen 4H

This is an interesting article. Most solids expand when they are heated. However, scandium fluoride, shrink when it is heated. This is because even though the bonds are stable, the fluoride atoms are free to move a bit. This mix of rigidity causes the crystal to buckle. Here’s the link: https://www....

Jingyao Chen 4H

Symmetry in the Lewis dot structure could indicate that it’s also symmetric when it is in 3D, but I would recommend just draw out the 3-dimensional figure and determine polarity based off of that.

Jingyao Chen 4H

They should be the same thing. I recommend that one the test, the safest way is to use the name that Dr. Lavelle uses in lecture slides.

Jingyao Chen 4H

A thing to remember is that there are polarity between bonds, and there’s also polarity of the overall molecule. Bonds could be polar, but in certain cases, because the molecule is symmetric, the overall molecule is not polar. Symmetry and the overall 3D shape is the thing that you should base off p...

Jingyao Chen 4H

I know we didn’t really go over ion dipole and ion induced dipole in class. However, I noticed that there’s also an intermolecular force called ion induced dipole. What is the difference between ion dipole forces and ion induced dipole forces? Is it similar to dipole induced dipole in the sense that...

Jingyao Chen 4H

Melting/boiling point depends on intermolecular forces. The stronger the forces, the higher the melting and boiling point. The reason that number of electrons and size matters is because larger molecules and more number of electrons contribute to higher LDF, which is still going back to LDF. Even th...

Jingyao Chen 4H

The energy of a bond that you are referring is probably the energy it takes to break a bond. In the very beginning, these values are experimentally observed. To calculate it, there is a formula: delta G = delta H - T*delta S, which we haven’t learned yet.

Jingyao Chen 4H

Intramolecular forces/bonds will always be stronger than intermolecular forces. For intramolecular forces, a good way to remember covalent bond is the strongest is to think that they are sharing electrons.

Jingyao Chen 4H

The answer above did a really good job answering the question. Just to add on, LDF is present in any molecules. This is the force that every molecule has, so don’t forget that when answering questions. Moreover, just a reminder that LDF is an very important force for molecules with large amounts of ...

Jingyao Chen 4H

Van der Waal Forces include dipole-dipole forces and LDF. In the lecture notes, however, Van der Waal is written as another name for LDF. I would recommend just use the name LDF when you are referring to the induced dipole moments between molecules.

Jingyao Chen 4H

For double bonds, two pairs of electrons are sharing, instead of one pair. Therefore, the bond is stronger, and therefore makes the two atoms closer to each other. Double bonds take more energy to break than single bonds.

Jingyao Chen 4H

It is correlated in someone. Polarity can be referred to in terms of bonds and in terms of a molecule as a whole. Within a bond, as long as the electronegativity of the two atoms are not the same, the result is a polar bond (unequal sharing of elections). In the context of a molecule, however, it’s ...

Jingyao Chen 4H

Adding on, free radicals is one of the theory regarding human aging. Some people believes that because of these free radicals that go around and damage cellular contents, the resulting consequence is the process of human aging.

Jingyao Chen 4H

This is a very interesting and exciting news! A catalyst consisted of platinum nanoparticles is able to cleave plastic’s carbon to carbon bond to produce liquid hydrocarbon, which could be further used to do a lot of work.
https://www.sciencedaily.com/releases/2 ... 075131.htm

Jingyao Chen 4H

Bond length refers to intramolecular forces, such as ionic bonding and covalent bonding. These intramolecular forces result in the formation of molecules and compound. The attractions between these molecules and compounds are intermolecular forces.

Jingyao Chen 4H

An easy way to remember the trend of electronegativity is to think about the concept of electronegativity. Electronegativity is the tendency to grab electrons. The atoms on the right side of the periodic table want to grab electrons to reach octet. Therefore, the electronegativity increases as you m...

Jingyao Chen 4H

Because electrons occupy greater volume, which means less repulsions, and therefore more stability.

Jingyao Chen 4H

Cations are ions that gets electrons stripped away. They lose electrons to reach octet to become more stable. On the contrary, anions likes to gain electrons to reach octet and become more stable. They are important because after ions are formed, ionic bonding can form.

Jingyao Chen 4H

During the lecture, copper is one of the exceptions. The electron from 4s2 moves to the e energy level because it’s more stable. Therefore, when one electron is needed to be removed, it is moved from the 4s1 level. Cr is also the other exception.

Jingyao Chen 4H

The electrons in 5s and 5p are in a high energy level than 4d. Therefore, valence electrons, and the electrons that gets stepped away first are in 5s and 5p.

Jingyao Chen 4H

Yes, we will be given a periodic table and most of the formulas on tests.

Jingyao Chen 4H

I believe it is just the next decimal place of the molar mass. It could be that we don’t need to go that far for using molar mass, but just for your information, the next decimal place is there.

Jingyao Chen 4H

Yes. It is a constant and is universally agreed/defined as the length traveled by light in a vacuum condition in 1⁄299792458 seconds.

Jingyao Chen 4H

Yes. Photons and electrons have both particle and wave light properties. They behave like waves together in a group. Moreover, based on the wave-particle duality, large objects have wave properties as well. However, this can’t really be proved because it’s hard to observe=serve, based in their large...

Jingyao Chen 4H

For these equations, the E in the equations are all energy for the energy of a photon, so the equations are interchangeable because they apply to the same thing. Therefore, you can decide which equation to use based on the variables you are given and the variables that you want to solve.

Jingyao Chen 4H

https://www.scientificamerican.com/article/how-do-the-chemicals-in-sunscreen-protect-our-skin-from-damage/ This article talks about uv’s damage on the skin and the mechanism of sunscreen. When UV shines on skin, it excites photons. When the electron falls, it releases energy which promotes biologica...

Jingyao Chen 4H

A research has shown that students who had protein drinks actually done better than students on caffeine! So next time when you want to study, try grab protein drinks, not coffee! :)

Jingyao Chen 4H

I’ve learned from my cluster professor today that when you drink coffee, the milk in the coffee actually has opposite effects, because the milk protein is sticky and binds to a lot of different things. So next time, when you want to drink coffee, go without milk or with soy milk! :)

Jingyao Chen 4H

I’m not a hundred percent sure if they will be on the test, but I feel like you should just try to learnt he conversions as early as possible :)
A lot of the future chemistry problems involve conversions, especially in thermodynamics.

Jingyao Chen 4H

Thank you Dr. Lavelle for making the concepts super easy to understand. You are a wonderful teacher. With your lectures, I was able to grasp new concepts in a very short amount of time. Thank you!

Jingyao Chen 4H

Thank you all for this info! Maybe I should practice doing homework with pen.

Jingyao Chen 4H

I’m currently in the same situation as you. One suggestion adding on to all the ones above would be trying to forget the fact that you’ve learned chemistry in high school. When I think that I’ve taken AP chem and have received a good score, I might not be as focused in lectures because I think that ...

Jingyao Chen 4H

Thank you so much for sharing this! I have just began this course, and I will make sure to follow your advice. Thank you!

Jingyao Chen 4H

For the rest of the problem, you can see that from all of the balanced equations, for every 8NaBr to be produced, 3Fe is needed. You can then start with the dimensional analysis. First convert the ton of NaBr to grams, then use molar mass to get the number of moles in 2.5ton of NaBr. Then you can us...

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