CHEMISTRY COMMUNITY

ngarcia

When interpreting line structures, how do you determine how many hydrogen atoms are present?

ngarcia

For the Chem 14A final, should we know how to determine if a molecule or ion is paramagnetic or diamagnetic?

ngarcia

If the complex ion (what is inside the brackets) is the cation, will it always be written first? And, vice versa if it is the anion?

ngarcia

I have noticed that two common neutrally charged molecules within coordination compounds are H2O and NH3. Are there any other common neutrally charged molecules that I should familiarize myself with in regards to coordination compounds?

ngarcia

How do you know when a coordination compound with 4 ligands form a tetrahedral complex or a square-planar complex?

ngarcia

When naming a coordination compound, how does the complex ion being the anion or the cation affect the name?

ngarcia

Can someone please explain the difference between pH and pOH?

ngarcia

On MyUCLA, there are two rooms listed for my final exam location. How do I know which one is the true location I have to go to for my exam?

ngarcia

A chelate is a complex containing a ligand that forms a ring of atoms that includes the central metal atom. Chelating ligands can bind cations tightly. Bidentate, tridentate, and hexadentate are examples of chelates.

ngarcia

Besides myoglobin and hemoglobin, what other biological applications of coordination compounds should we be aware of?

ngarcia

When writing out hybridization notation, does the d orbital come before s and p? For example, "dsp^3" instead of "sp^3d."

ngarcia

If my discussion is on Thursday (Thanksgiving Day), when would I turn in my Week 9 homework assignment?

ngarcia

In today's lecture, Professor Lavelle used cis-dichloroethene as an example of a polar molecule and trans-dichloroethene as an example of a nonpolar molecule. This made me very confused because they have the same structure (according to the powerpoint), but the arrows were in different areas. Can so...

ngarcia

Do the numbers accompanying the A, X, and E depend on electron pairs or individual electrons?

ngarcia

Just to be safe, I would familiarize myself with all of the VSEPR shapes.

ngarcia

We haven't gone over hybridization yet, so I would not expect it to be on the test. However, Professor Lavelle did say that he has one more page of information (which he will be going over in Monday's lecture) that will also be included on the test.

ngarcia

A molecule with a seesaw molecular geometry means that the molecule has four bonding pairs and one lone pair.

ngarcia

How do you know when a bond angle is "slightly less" than the expected bond angle measure?

ngarcia

Yes. Typically, the atom that is alone or has the lowest quantity in the formula is at the center of the Lewis structure.

ngarcia

Also, note that dispersion forces, induced-dipole-induced dipole forces, London forces, and Van der Waals forces are all the same.

ngarcia

Why does a hamburger yield lower energy than a steak?

Because it's in the ground state.

ngarcia

Why did the white bear dissolve in water?

Because it was a polar bear.

ngarcia

Laughing Gas: He He He

ngarcia

Does "Ep" stand for potential energy? Or something else?

ngarcia

I told a chemistry joke...

there was no reaction.

ngarcia

Does the arrow that represents the dipole always point toward the negative charge?

ngarcia

Can someone give me an example of solving for a dipole moment using numerical values? Is the charge (q) used in the dipole moment formula determined by their group on the periodic table?

ngarcia

Highly distorted electrons are described as being highly polarizable. But, how do you determine if an electron is a highly distorted electron?

ngarcia

If ionization energy and electron affinity are high, then an atom will have high electronegativity. Does this mean ionization energy and electron affinity positively correlate with electronegativity?

ngarcia

Even though we have our midterm next week, will we still have five textbook problems and five chemistry community posts due?

ngarcia

What is a resonance hybrid? How do you determine how to draw a resonance hybrid?

ngarcia

When drawing Lewis structures, should I always aim for a 0 formal charge? Is this possible for all Lewis structures?

ngarcia

What are the exceptions in drawing Lewis structures?

ngarcia

Can someone please explain why the electron configuration chart shortcut is inaccurate? If I use it, how must I change my answer to be correct?

ngarcia

Can someone define an effective nuclear charge? What makes it an effective nuclear charge?

ngarcia

In today's lecture, Professor Lavelle's PowerPoint noted two exceptions that we need to know when determining atomic states/orbitals. Under "need to know two exceptions," the slide said "half full d^5 and full d^10 subshell have lower energy." Did I misunderstand what the two exc...

ngarcia

In today's lecture, Professor Lavelle brought up how 3d comes before 4s, contrary to what most of us learned in high school. Can someone explain why this is the case?

ngarcia

Will Professor Lavelle ever ask us to draw out orbitals and their corresponding planes for future tests?

ngarcia

Can someone please explain why particle properties stop electrons from being ejected when light intensity increases. Thank you!

ngarcia

So, I understand how allowed values are determined for the magnetic quantum number. However, I am confused about how you determine the base (x, y, or z) of the orbital. In today's lecture, Professor Lavelle's example gave n=2, l=1, and m-base l=-1. The answer was that the electron was in a 2p-base x...

ngarcia

According to SI units, mass is in kg. Nevertheless, always make sure you keep your units consistent while doing the math, especially when you have to deal with kg vs. g. Then, convert into the desired units at the end.

ngarcia

The diffraction patterns that are produced by electrons are similar to those of water waves when they enter two holes in a barrier to create separate wave fronts that combine and interact with each other. These waves can be formed from constructive interference (waves in phase) and destructive inter...

ngarcia

Just to clarify, increasing light intensity increases the number of photons. And, if, and only if, the energy per photon is greater/equal to the energy needed to remove an electron, then increasing light intensity results in more ejected electrons. However, one cannot assume that electrons are being...

ngarcia

https://phys.org/news/2019-10-approach- ... cular.html

For everyone in Lavelle's Chem 14A lecture going over The Quantum World.

ngarcia

Thank you so much for sharing your bits of wisdom with us! I will definitely reach out to you if I come across obstacles this quarter and the next.
While you were at UCLA, did you overlap biology and chemistry? If so, what was that like? Any advice for balancing and keeping up with both?

ngarcia

Hi all,

For our first test, will it mostly consist of math-centered problems or will it also include vocabulary-related questions?

Thank you!

ngarcia

How far off were your calculations? If they were close enough and were able to get you to the correct answer, then I think you're doing great!

ngarcia

Are there any compound formulas that we should know by heart going into this course, especially once we get to writing out chemical equations ourselves?

ngarcia

To solve problem G 19 Part B, I calculated the number of moles of HCl I would get from 25 mL of 0.366 M HCl. This would equal 9.15x10^-3 mol HCl. Then, take that answer and divide it by 125 mL to solve for the molarity of the diluted solution. The answer you get is 0.073.

ngarcia

Hi all,

I am currently working on problem G.25. If you dilute 10. mL of a solution and double the volume 90 times, would you simply multiply 10. mL by 90 and cancel out the mL/L with the molar concentration of the substance to find the number of molecules (using Avogadro's number)?

Thank you!

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