CHEMISTRY COMMUNITY

Omer Lavian 2K

Dear Professor Lavelle, I just want to say that I am honored to have been a part of your class. You are one of the sweetest and most caring teachers I have had the pleasure of learning from both within and outside of UCLA. I cannot tell you how much I appreciate the amount of resources you provide f...

Omer Lavian 2K

Congratulations!

Omer Lavian 2K

A really deep and important question to ponder as you study for quiz 3 and the final.

Omer Lavian 2K

What in titration is organic chemistry?

Omer Lavian 2K

One thing to keep in mind about this that is kind of counterintuitive to me is that neutral halogens are considered electrophiles. When I think of halogens, I automatically remember that they tend to have a -1 oxidation state, which made it hard for me at first to grasp that NEUTRAL halogens actuall...

Omer Lavian 2K

Yes! You're exactly right! The trick is just to know that the order of the reaction and the order for each reactant are separate things.

Sometimes the order of the reactant and the reaction are the same value, but they still represent different things.

Omer Lavian 2K

I heard from someone that there you're "not supposed" to take Chem 14BL at the same time as Chem 14C. Is there some sort of issue with that? Is the workload of those two classes combined considered extremely overwhelming?

Omer Lavian 2K

A galvanic cell uses a redox reaction to create a flow of electrons (current) that can do useful work. For a galvanic cell to work, the redox reaction used must be thermodynamically favorable (delta G must be less than 0, which is the case for a spontaneous reaction), creating a positive voltage. Fo...

Omer Lavian 2K

How does the crystal with no entropy feel?

0 K

Omer Lavian 2K

This question is more conceptual than it is mathematical. If you think back to the equation with Boltzmann's constant, S = KblnW, you see that the entropy depends on W, the number of possible states (often called microstates) in which a material (an atom, a molecule, a substance, etc.) can exist. Th...

Omer Lavian 2K

The problem is asking for the heat capacity of the calorimeter, not the specific heat capacity of the calorimeter. Long story short, if you don't see the words "specific" or "molar" before "heat capacity," then you don't need to worry about mass or moles.

Omer Lavian 2K

If it's any help at all a guide to integration of polynomials and of x^-1 (also known as 1/x) can be found on the constants sheet.

Omer Lavian 2K

Which homework problems go over the heat capacity/calorimetry material we talked about last lecture?

Omer Lavian 2K

What do you call 6.02214 x 10^23 big, white bears?

MOLAR BEARS!

Omer Lavian 2K

I mean water is neutral, so I assume the charge corresponds to the ion and thus the entire complex.

Omer Lavian 2K

Determine whether an aqueous solution of each of the following salts has a pH equal to, greater than, or less than 7. If pH & 7 or pH ' 7, write a chemical equation to justify your answer. (a) NH4Br; (b) Na2CO3; (c) KF; (d) KBr; (e) AlCl3; (f) Cu(NO3)2. I understand that Al3+ and Cu2+ are small,...

Omer Lavian 2K

I know this is explained in the course reader, but it's super confusing to me. How do we determine the correct sig figs when doing a logarithm (for example, to find a pH from an H3O+ concentration) and when using exponents (for example, to find an H3O+ concentration from a pH)?

Omer Lavian 2K

A reactor for the production of ammonia by the Haber process is found to be at equilibrium with PN2 " 3.11 bar, PH2 " 1.64 bar, and PNH3 " 23.72 bar. If the partial pressure of N2 is increased by 1.57 bar, what will be the partial pressure of each gas once equilibrium is re-establishe...

Omer Lavian 2K

(a) Draw the bonding and antibonding orbitals that
correspond to the &-bond in H2. (b) Repeat this procedure for
HF. (c) How do these orbitals differ?

Are we expected to determine the shape of molecular orbitals?

Omer Lavian 2K

(c) Assuming that the initial pressure of X2 was 0.10 bar, calculate the value of K for the decomposition. We are given the original pressure of X2 and are expected to calculate partial pressures based on that for the equilibrium condition of X and X2. Shouldn't we be given the pressure of the syste...

Omer Lavian 2K

Nina, to answer your question, and maybe this will help with the original question as well, for a molecule to be polydentate, it needs to be able to contribute multiple lone pairs at the same time to a central metal atom. This means that a) there must be at least two atoms with available lone pairs ...

Omer Lavian 2K

Sorry for posting so much but Liam, I remember Dr. Lavelle drawing the molecule in class with an N-C-C-N structure. I assume that this gives all the N's a formal charge of zero, whereas you have one N with a -1 charge and another with a +1.

Omer Lavian 2K

Also the SO42- ligand has 4 atoms with lone pairs, but it isn't shaped in a way that would indicate that it is tetra dentate. My guess is that like carbonato, it can be mono or bidentate. Thoughts?

Omer Lavian 2K

Also the SO42- ligand has 4 atoms with lone pairs, but it isn't shaped in a way that would indicate that it is tetra dentate. My guess is that like carbonato, it can be mono or bidentate. Thoughts?

Omer Lavian 2K

17.33 Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center: (a) HN(CH2CH2NH2)2; (b) CO3 2!; (c) H2O; (d) oxalate. What makes a ligand able to be polydentate? Addition...

Omer Lavian 2K

Arrigato Mr. Sulfato!

Omer Lavian 2K

I saw someone ask a question about hybridization beyond sp3 here. Will we be expected to know about that for the midterm, the final, or for any other parts of this course?

Omer Lavian 2K

Thank you!

Omer Lavian 2K

3.111 A common biologically active radical is the pentadienyl radical, RCHCHCHCHCHR%, where the carbons form a long chain, with R and R', which can be a number of different organic groups, at each end. Draw three resonance structures for this compound that maintain carbon’s valence of four. I'm conf...

Omer Lavian 2K

To answer your first question, IN GENERAL, going from left to right across a period on the periodic table, ionization energy increases because while the principle quantum number stays the same (or goes down one in the case of period one elements), the positive charge of the nucleus increases slowly ...

Omer Lavian 2K

I think I figured out the issue. The answer shows that sulfur can still have a formal charge of 0 without breaking the octet rule. I suppose that means that breaking the octet rule should be a last resort for if the formal charges can be brought closer to 0. It doesn't seem to be necessary in this e...

Omer Lavian 2K

I can't figure out how to post a picture on this forum! I wish I could so we can look at it together. The way I drew it gave sulfur two double bonds and two single bonds, giving it a formal charge of 0.

Omer Lavian 2K

The problem asks to write the Lewis Structure for HSO3-. The solution manual bonds the hydrogen to one of the oxygen atoms, but can't you bond the hydrogen atom to the sulfur atom? With an expanded octet, the formal charge of sulfur is zero either way, and the only atom with a non-zero formal charge...

Omer Lavian 2K

Let's use the example of benzene. As you can see on page 81 of the course reader, there are two different possible Lewis structures for benzene. In this case, this simply means that the double bonds and single bonds in the ring can be rearranged, resulting in two different possible Lewis structures....

Omer Lavian 2K

Thank you!

Omer Lavian 2K

Determine whether each of the following electron configurations represents the ground state or an excited state of the atom given. I can't pull up a picture of the diagrams for the problem for some reason, but here are the configurations given, at least based on how I interpreted the diagrams. (a) C...

Omer Lavian 2K

Thank you!

Omer Lavian 2K

Delta E doesn't represent energy. It represents a change in energy. If an electron transitions from a higher principal quantum number to a lower one, it releases energy, causing a negative delta E and the release of a photon (Think about it this way. If you applied the same equation to a shrinking b...

Omer Lavian 2K

1.) Yes. Generally speaking, photoelectric experiments are performed using UV light since it often has sufficient energy to eject electrons from metals. 2.) Yes, I also got 1.99 x 10^-18 J for one photon for question #16. Just good old fashioned E=hv. You seem to have that in the bag! For question #...

Omer Lavian 2K

Number 13 in the Pre-Module Assesment for the Heisenberg Uncertainty Principle states: Two students are 'studying' together when Bob says "I do love you Alice" and Alice responds "But how can I be sure?" Would using Heisenberg's uncertainty principle help them determine or resolv...

Omer Lavian 2K

Homework problem 1.11 asks: In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series (for example, Balmer series, Lyman series, Paschen series), as shown in Figs. 1.10 and 2.1. What is common to the lines within a series that makes grouping them to...

Omer Lavian 2K

Imagine two sine waves (sort of like the waves Dr. Lavelle has drawn for us in class) of the same wavelength, frequency, and amplitude (distance from the equilibrium position, the point between the peak and the trough, to either a peak or a trough). If the peaks of one wave line up with the peaks of...

Omer Lavian 2K

Hey I'm so down for this. I live in building C!

Omer Lavian 2K

You've never heard of sodium hydroxide? It's so basic!

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