CHEMISTRY COMMUNITY

Omar Selim 1D

It is reaction dependent and there is no general assumption that can be made unless give the problem's specifics

Omar Selim 1D

Lavelle's emails provide all the information we need to know about the final.

Omar Selim 1D

Regular calorimeters assume constant pressure while bomb calorimeters assume constant volume. They are both isolated systems

Omar Selim 1D

He said he'd update us tomorrow so I feel like we shouldn't worry or stress about it right now and instead just focus on studying and it'll work out.

Omar Selim 1D

People can stay focused in different ways. I like to drink coffee or tea while i study because it keeps me awake and alert

Omar Selim 1D

I think we can assume that the final will include about equal amounts of most outlines

Omar Selim 1D

The final will be take-home and straight forward according to the email sent a few hours ago.

Omar Selim 1D

The study guide would be all of Lavelle’s outlines from the beginning of the quarter

Omar Selim 1D

You should have 100 posts

Omar Selim 1D

Convention states that the anode (oxidation) should be on the left

Omar Selim 1D

We will probably get them back in time before the final to look over it

Omar Selim 1D

I remember the question. For that, you needed to consider enthalpy change by relating equations

Omar Selim 1D

Lavelle mentioned in class that test 2 will cover outline 4 (that wasn't on the midterm) and outline 5. It is important to understand that none of the concepts can be taken in isolation and an understanding of previous concepts and outlines is necessary to do your best on test 2.

Omar Selim 1D

Fundamentally, oxidation happens at the anode and reduction happens at the cathode. In terms of writing it out, you typically include the anode on the left and the cathode on the right.

Omar Selim 1D

You have to differentiate between the ions you are looking at. One of the elements gains electrons while the other loses. the mnemonic to help you remember the definitions of oxidation and reduction if that was your confusion is OIL RIG: Oxidation Is Losing; Reduction Is Gaining.

Omar Selim 1D

I don't believe there is a difference in efficiency. They serve the same purpose in balancing charges and the distribution of ions.

Omar Selim 1D

Hi everyone,
My question refers to salt bridges and what they provide to each part of the diagram. I was confused on how they play a role in balancing charges? Do they provide electrons to one side or ions? Also, why don't they dissociate completely dissociate in the solutions they're in?

Omar Selim 1D

A salt bridge essentially allows the "circuit" to be complete. It allows for a constant flow of charge without an immediate stop as a result of charge build-up. It essentially balances charge in ot=rder to keep the system going.

Omar Selim 1D

There is no curve in the class, but points and grade correlation are not determined until after the final exam has been posted. Your scores on the tests are not indicative of what your final grade will come out to be as Dr. Lavelle might adjust it slightly at the end of the quarter depending on what...

Omar Selim 1D

The material covered in test 2 will not include information from the coming weeks. He postponed it in order to give us more time to study for it.

Omar Selim 1D

In order for a reaction to be considered spontaneous, the value of delta G must be a negative number. delta g = delta H - TDELTAS. If delta g is 0, the reaction is at equilibrium.

Omar Selim 1D

I believe the best way to understand the concept of a salt bridge is to liken it to a closed circuit. In order for a circuit to be complete, there must be a closed-loop in order for charges of positives and negatives to get balanced and have somewhere to go. The salt bridge essentially completes the...

Omar Selim 1D

Hi all,

So I'm having trouble figuring out when to use delta G = -RTlnk vs. the other equations for delta G. Is there a reason you would pick one equation over another? and what do you do differently when it is determined at constant pressure vs. volume

Omar Selim 1D

On his syllabus it says that he does not curve but that grades will be determined at the end of the quarter

Omar Selim 1D

An adiabatic system means that the system is isolated and therefore delta U = w + 0(q)

Omar Selim 1D

Yes, however, it is helpful to know the equations before hand because the units, definitions, and terms are not provided

Omar Selim 1D

Yes, it is one of the topics Lavelle discussed in lecture and it is included in outline 4

Omar Selim 1D

Are there video outlines for any of the recent topics?

Omar Selim 1D

How do we access the course reader?

Omar Selim 1D

Which equations should we memorize/ will need to know off the top of our heads for the midterm?

Omar Selim 1D

Internal energy is just the energy found within a system without any interference from the world beyond. It is the concept of energy only being from the kinetic and potential energy already found within a system

Omar Selim 1D

Is enthalpy just the change in energy? what does it mean to have a positive or negative change in enthalpy? When would such changes occur?

Omar Selim 1D

I am still a little bit confused on the difference between a closed and isolated system. Could someone provide the definitions and explain the differences?

Omar Selim 1D

Since the midterm is soon, you can pick any of the topics we've already gone over. It might be most helpful to review topics from the most recent lectures

Omar Selim 1D

Diatomic molecules such as H2, O2, N2, F2, I2, CL2, and Br2 all have an enthalpy of formation of 0 because it is their naturally occuring state. There is no enthalpy of formation for the way something is already formed. However, if you were to change the molecule, then there would be an enthalpy of ...

Omar Selim 1D

As long as all the calculations are correct and the units match up then you can use either one. However, changing units constantly may result in accidental mix ups, so you should be fine as long as you stay consistent

Omar Selim 1D

A bomb calorimeter is a more robust and accurate calorimeter. It can withstand more pressure, so it is typically more often used

Omar Selim 1D

In an isolated system, energy is transferred, so q=0, q=0, and delta u also equals 0

Omar Selim 1D

A solvent is the substance in excess that other reactants are being dissolved in. E.g. Water is a solvent. Salt is a solute

Omar Selim 1D

In an exothermic reaction, heat is found on the right side of the equation, therefore, by adding heat, you would shift the reaction away from where there is an excess so it would shift to the left (reactants).

Omar Selim 1D

I would email the TA from last quarter's discussion section asking when a good time would be to come and pick up the tests

Omar Selim 1D

Temperature and heat are different in that for a sample of boiling water, the temperature would remain the same until it undergoes a phase change while heat would be continuously added

Omar Selim 1D

Steam causes burns due to the high amount of heat transferred from the steam to skin. It has a large Q and H value.

Omar Selim 1D

All the necessary information regarding what is needed for a problem would be provided. It is best to know how to calculate Delta H in case it is one of the values unaccounted for, but otherwise, it would be provided. We are not expected to memorize any values.

Omar Selim 1D

Ask your TA because it varies depending on the TA's preference. Just to be sure, I recommend posting at least 5 times a week.

Omar Selim 1D

A stress applied to the system is any altercation made that shifts the reaction rates. Stressors include temperature, pressure, the removal or addition of a product or reaction, and the addition of a different reactive sbstance

Omar Selim 1D

Energy is released when bonds are formed because the atoms go to a lower energy state that is more stable.

Omar Selim 1D

I would read the textbook first as it is the most in depth review of the lecture material you could get. I would then review the lecture notes then do the homework, going over how to approach the homework problems if you get them wrong.

Omar Selim 1D

Kw = 1.0 *10^-14 is the equilibrium constant for water, which is also defined as Kw = Ka * Kb. The two definitions you gave are interchangeable for the most part

Omar Selim 1D

Dr. Lavelle has the test and exam schedule on the class webpage. For test 1, it will be starting on Tuesday the 21st in your discussion section

Omar Selim 1D

Test 1 is starting on Jan 21st in your discussion section. Dr. Lavelle has the tests/exam schedule up on the class page

Omar Selim 1D

The TAs said that it is graded based on a demonstrated effort of answering 5 questions. This is due to the fact that we have access to the solution manual so grading on how many are correct wouldn't be as effective and would dissuade students from actually trying

Omar Selim 1D

Outline 1 and everything mentioned in the assigned readings/homework assignments/lectures. I believe that test 1 will hold us accountable for everything up until the lecture right before the test

Omar Selim 1D

The best way to determine that is through lectures and the readings on the syllabus. I believe that in the syllabus Dr. Lavelle mentioned that 1 question on every test will be from the homework problems, so those are also a great way of studying.

Omar Selim 1D

You'll be able to start picking them up next week from Young Hall. Room 3034 I believe. I'm not sure when the last day to pick them up is but Dr. Lavelle sent out the info in an email a few weeks after the final.

Omar Selim 1D

It is helpful to understand the general proportionalities between the different units of pressure because although we will be getting a conversion sheet, sometimes you may have used a wrong conversion that you could easily identify based on what you would approximate it to be.

Omar Selim 1D

What is a hydrogen bond site? and for hydrogen bonding to occur do both compounds need to contain a hydrogen bonded to F O or N or can you have one compound that involves a bond between H and F O or N and the other compound to just be an F O or N not bonded to a H. For example is the bond between H3...

Omar Selim 1D

Do you hybridize coordination compounds and the ligands they contain? and if so how?

Omar Selim 1D

There are also certain ones you should commit to memory. Those being:
EDTA (can be hexadente)
Ethylenediamine (can be bidente)
diethylenetriamine(can be tridente)
oxalato (can be bidente)

Omar Selim 1D

Are we expected to know how to draw different coordination compound structures? do we need to know how to draw chelating coordination compounds?

Omar Selim 1D

to what extent do we have to understand the topic of isomers and the idea of cis vs trans? do we have to be able to identify different types of isomers on the final?

Omar Selim 1D

It would be helpful to understand the general concept. The equilibrium constant is set up mainly to show what the reaction favors and what the complex's ligands are most likely to be. When analyzing reactions involving the equilibrium constant, it is generally a formation of the products over the re...

Omar Selim 1D

Most likely, I would assume, they would be up by Wednesday's lecture in order to give us adequate time to go over them before the final

Omar Selim 1D

consider lewis structure, orbitals, and electron pairs which also get hybridized

Omar Selim 1D

It is material that most likely will be covered in the next lecture but if you are preparing early, it is always better to over prepare than under prepare

Omar Selim 1D

I would assume it would not be on the final and that only lecture content and readings will be covered

Omar Selim 1D

The final will be cumulative of everything since the beginning of the quarter

Omar Selim 1D

I feel like it would be best to prepare with the mindset that all topics would be covered equally

Omar Selim 1D

sigma bonds are harder to break than pi bonds because the former are a result of end-to-end bonding while the latter consist of side-to-side bonds

Omar Selim 1D

Are hydrogen bonds stronger or Ion-dipole?

Omar Selim 1D

Ionic character depends on the difference in electronegativity values. The greater the difference, the more ionic

Omar Selim 1D

It all has to be memorized, but i found that ionce you understand 1 row, the rest become easier

Omar Selim 1D

The boiling point and melting point depend on the strength of the bonds. Typically stronger bonds mean a higher boiling/melting point

Omar Selim 1D

The letters represent: the central atom, bonds, and lone pairs
- A = Central atom
- X = Bonds
- E = Lone pairs

Omar Selim 1D

The best way to determine whether or not a molecule is non-polar or polar is by analyzing the vectors of electron distribution and pulls depending on electronegativity

Omar Selim 1D

Because each element has different bond lengths depending on what it is being bonded with, we would probably be given the bond lengths in a question

Omar Selim 1D

We talk about hybridization a lot, but what does it actually mean for certain bonds to be hybridized? and do we hybridize all molecules?

Omar Selim 1D

The result of higher strength intermolecular forces, resulting from the hydrogen bonds between the water molecules, it is harder to break apart those bonds, which causes surface tensions

Omar Selim 1D

For anions, polarizability increases the more electrons it has. For cations, it depends on how small and how charged the ions are

Omar Selim 1D

Yes, electronegativity describes the pull of electrons. It increases up and to the right of the periodic table

Omar Selim 1D

You don't know the mass of a photon so debroigle's equation would not be applicable

Omar Selim 1D

When thinking about what defines an orbital or subshell with respect to quantum numbers, Ml would refer to orbitals while L refers to the s, p, d. f,.. subshells.

Omar Selim 1D

It is either on My UCLA under "discussions" or the actual lecture

Omar Selim 1D

There's less energy in the 3rd energy level than the 4th, because of the reality that it takes more energy to maintain stability in the 4th energy level

Omar Selim 1D

There's no formula but there are very specific lengths for certain bonds that I doubt will be expected knowledge to know on the test

Omar Selim 1D

It's good practice to understand the whole concept of valence shells, but also understand that the bohr model is not always representative of reality

Omar Selim 1D

Elements in row 3 and beyond is usually the rule of thumb because they have empty orbitals

Omar Selim 1D

The homework problems are helpful once you already understand the information so I recommend going to review sessions/ watching helpful chemistry videos then doing the homework problems slowly and making sure you understand why you got a certain answer

Omar Selim 1D

When thinking about electron affinity think about how close the electrons are to the nucleus (where the protons are). Electron affinity increases the closer the electrons are to the nucleus, so it increases as it goes up and to the right

Omar Selim 1D

Do different resonance structures affect the polarity of molecules?

Omar Selim 1D

Ionic bonds occur after electrons have been completely transferred over while covalent bonds are the sharing of ekectrons.

Omar Selim 1D

Probably try to be as accurate as possible but you don't have to be exact. As long as you have the right attempt, you don't need to use a protractor or anything that specific

Omar Selim 1D

Possibly because the light is not diffracted enough due to the size of the water droplet, or the rainbow could be very small and hard to notice

Omar Selim 1D

Molarity is moles/liters. It refers to the concentration of atoms/molecules in a solvent. When something refers to transferring a specific molarity of a substance, it is talking about a certain concentration of that liquid

Omar Selim 1D

Our TA said grades would be input as soon as assignments go in and they can be checked on MyUCLA

Omar Selim 1D

Ionization energy is the amount of energy it requires to remove an electron from an atom's valence shell, which is similar to the definition of work function

Omar Selim 1D

The constant refers to the amount (6.022*10^23) in a mole of a unit. It could be either a molecule, or an atom as long as it is 1 unit.

Omar Selim 1D

Sig Figs are important and you should keep them in mind while you're doing a problem but only round at the end

Omar Selim 1D

Why does a shorter wavelength mean there is more energy?

Omar Selim 1D

Electronegativity is the strength atoms have in puling other electrons to complete their valence shell

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