CHEMISTRY COMMUNITY

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kinetics determines the speed of a reaction so it deals with the rate of a reaction. thermodynamics determines the energy/heat that is required/released from a reaction.

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kinetics determines the speed of a reaction so it deals with the rate of a reaction. thermodynamics determines the energy/heat that is required/released from a reaction.

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what does it mean for a gas to be ideal monoatomic

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ΔGº is the standard free energy which means the free energy at standard state, 25 degrees C/298K while ΔG is the free energy at any particular temperature.

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At lower temperatures, the particles have less energy and moves around a lot slower compared to a higher temperature. therefore, less particles are colliding into each other to continue a reaction.

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I believe changing the temperature in which the reaction is happening and adding a catalyst would cause a change in the rate constant.

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dP/dt shows the instantaneous rate in which the product is formed.

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intermediates are usually not seen in the overall reaction equation because it gets consumed while catalysts are included and it is used to help speed up a reaction by lowering the activation energy of the reaction.

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I believe stoichiometric coefficients and reaction rate orders are not related.

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how do you know that you have to separate the fe and o as o2?

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you would use the half reactions which includes the number of electrons transferred and can be determined by looking at the charge differences. then you make Sure both half reactions have the same number of electrons transferred so you might have to multiple one or both by a number and this would fi...

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Enot is when the reaction is under standard conditions and you would take the enot value of the reduction half minus the enot value of the oxidation half to get the cell potential aka enot. for e, it is for reactions not under standard conditions and you would use the Nernst equation

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yes I believe so. the presentation where he first talks about kinetic is the start of a new outline which is not on the midterm

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n for these problems is just the number of electrons that are being transferred and you can do this by splitting the equation into the two Half reactions. then you want to make sure that both reactions have the same number transferred so you might have to multiple one or both by a certain amount.

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why are molecules considered oxidized when they gain an element for example NO2- to NO3-

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what is an easy way to remember how to calculate oxidation numbers?

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definitely some pixar originals like monster inc

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how would a closed system be able to exchange energy

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im planning to do both 14bl and 14c next quarter

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delta u = 0 when both q and w are 0 or if the heat cancels out with the work

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a positive delta s means the reaction can continue spontaneously while a negative delta s means the reaction is not able to continue spontaneously

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what is the difference between a closed system and an isolated system?

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if work is being done on a system then it would be positive

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exothermic reactions are reactions where more energy is released than actually absorbed. therefore, it is easier for more reactions to release energy rather than find energy to absorb to continue reactions

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I was told that the number of posts was counted at the end of the quarter but its suggests to do 5 posts a week so you are able to be up to date with your posts n also get help with current topics of the week

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definitely feel that. usually get super stressed when a lot of my work starts loading up but ill take one day to really just relax and not think about school work. I like to go outside and just enjoy nature and one day of not doing work is not going to hurt.

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when q<k that means that there are more reactants which also means the the forward reaction is favored to create more product

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I remember working on one of the achieve homework and the feedback told me to think about the relationship between Cv and Cp and I am not sure how they are related. Can someone please explain it?

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q will be a negative value when it releases heat aka an exothermic reaction. on the other hand, a positive q value would be when a reaction requires heat aka an endothermic reaction.

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I've been having a little bit of trouble with this problem as well. I was able to get the correct answer for part b but im not sure what I am doing wrong when calculating path a when I am following the equations like the other responses are saying. I use the ideal gas law to find the number of moles...

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cp is heat capacity for constant pressure while cv is the heat capacity for constant v.

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Delta U = qv if the reaction is done under constant volume. This is because in constant volume, there can be no volume change no there is no work of expansion. Therefore, w=0, so the equation deltaU = q + w just turns into deltaU=qv where qv is the heat transfer of a system under constant volume. w...

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hi can someone please explain the key points of external and internal pressures? is internal pressure what is going on inside a beaker? I'm a little confused about external pressure

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hi, can someone give a summary of what kind of thermodynamic problems we are doing? I'm a little confused with what is going on in the lectures at the moment. what type of problems would we use the integral to solve or was that just a conceptual thing?

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I think usually these problems are expressed by kj but some problems may ask for something different.

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melting would be considered an endothermic reaction because heat is required for a solid to melt into a liquid.

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what I've done to study last quarter was to take notes of the notes I took in lecture so I end up with a more compressed version of my notes. I also like to do the practice problems that are listed on the syllabus for more help n practice.

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when removing a reactant, the reaction would then shift towards the reactants to make up for the "missing" reactant when in equilibrium

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percent ionization is typically only important for the use of problems with weak acids/bases. it tells us the amount dissociated in a solution which would help us find the [H3O+] or [OH-] produced. To find the numerical value of the percent ionization, you would take the calculated amount of H30+ or...

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with problems that involve calculations, I typically do not round until the last step so I would keep the value of x on my calculator and use that to calculate the ph and then rounding to the needed sig figs after.

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k would refer to the general equilibrium constant but with reactions dealing with acids and bases, Ka can also be used to describe the acidity constant while Kb would be the basicity constant

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when you see that a reaction's Q is equal to its K value, then that means the reaction is at equillibrium

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everything but liquid and solids are included with the calculations of an ICE table

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with equilibrium problems I like to think of the reaction as a scale. if something is added to one side, the other side must increase as well to balance it out. with endothermic reactions, heat is added to the reactant side so as a result, more products will form, favoring the products side. with th...

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spectator ions are the ions in a chemical reaction that don't change so it would be seen in both the reactants and products side. they're usually taken out since they don't do anything to the equilibrium constant or any other calculations.

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solids and liquids are not used in the equilibrium constants so it would not have an effect due to the reaction changes.

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Le Chatelier's principle just makes sure that a reaction is at equilibrium by shifting the reaction into different directions depending on the changes that have been made to a certain reaction.

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When there is a solid or liquid in an equation for an equilibrium problem, do we include its numbers to calculate K or Q or do we only use the numbers for (aq) and (g).

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Both Q and K is calculated with products/reactants. When Q is greater, that would mean there are more products in the reaction so a reverse reaction would occur to get the reaction back to equilibrium by producing more reactants.

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yes. whenever q=k that means that the reaction is at equilibrium.

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I think someone had this question in my discussion. I believe my ta said that for gasses, Kp would have to be used.

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yes, sigma bonds are always the first bond to form and pi bonds will be formed after this and the number of pi bonds would depend whether its a double or triple bond

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a ligand is just a compound that is attached to the central metal atom

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I did not even think about memorizing the biological compounds but now that I have seen your post I will definitely go over them again. thanks for the reminder!

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yes, I believe he did mention something about the 3+ charge on the Fe

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thank you shiley! I have been kinda confused with lewis and bronstead acid and bases and this simple explanation made it a little more easier to understand.

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Dr. Lavelle,
It has been really nice to be in your class during my first quarter at UCLA. Thank you for putting so much effort into providing so many extra resources to make sure we succeed. I am looking forward to another quarter with you in 14b.

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the conjugate base is basically the atom that would accept the proton if the reaction were to be reversed.

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I think it Is a good idea to know them but I wouldn't stress too much about it bc I remember my ta saying that the finals will be more focused on the longer topics that we went through and the acid base section was not too long.

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the percent yield equation is actual yield, which is the amount you get from an experiment, divided by the theoretical yield, which is the amount of product you should get that you calculated multiplied by 100 to get the percentage

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I emailed my ta and he told me the questions I got wrong but to get more details you would have to go to office hours.

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I like to listen to music and also sit outside with no distractions to relax.

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a non polar molecule is a molecule where the dipole moments in the molecule all cancel out, usually there would be the same atom all around and the center atom doesn't have any lone pairs. a polar molecules is a molecule where the dipole moments do not cancel out so there will be a net dipole moment...

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the strength of the intermolecular forces of the molecules is one of the most important factors of determining the boiling/melting points.

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VSEPR stands for valence-shell-electron-pair-repulsion and its a 3-d model of the lewis structure which shows the shape of molecules more accurately.

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it would be the most stable when the formal charge of the central atom is 0

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formal charge is for all elements in a molecule. usually it is best to have a formal charge of zero on all atoms in a molecule and if the molecule has a charge then the formal charge should match up to that charge

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I dont think electronegativity and charge have a correlation. I would usually just use periodic table trends to help me compare electronegativity of different atoms.

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what does it mean for a molecule to contain a delocalized pi bond?

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yes that would be fine, the [Ne] tells you the electron config for ne with 10 electrons. as long as the rest of the config matches the number of electrons of the atom, it should work

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there isn't a set rule on what type of bonds you should use. rather try focusing more on formal charge and getting all the atoms to have a formal charge of 0

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in covalent bonds, electrons are shared between two atoms. however, in ionic bonds, one atom/element is donating an electron to the other atom/element.

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double bonds are shorter because more electrons are being shared between two atoms. therefore, they are more attracted to one another and pulled in more leading to a shorter bond length compared to a single bond.

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what is the difference between electronegativity and electron affinity? do they both not talk about an element being attracted to another element?

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a resonance structure simply means that there is a bond in the lewis structure that can be moved around without changing the components of the lewis structure. any one of these resonance structures should be fine.

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I just remember this by drawing arrow on my periodic table. ionization energy, electron affinity and electronegativity all increase from left to right and down to up while atomic radii increases from right to left and up to down

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the other one would have a double bond between the other o and c

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905775737 wrote:I was having trouble downloading the software, so I had to go into my settings and change some stuff in the privacy settings. I had to manually "allow" the software to be downloaded.

are you using a MacBook?

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is anyone else having issues with loading the midterm practice problem on respondus? I've tried multiple times but I only see a white screen and in the upper right corner, when I hover over an icon, it says that the site is blocked or something similar to that. does anyone know what to do to fix this?

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I think I remember my ta saying we can take the exam on our iPads, but I was wondering if we are allowed to use our iPad as "scratch paper" or do we need physical paper n pencil.

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a unit with a negative exponent like s^-1 simply just means it is "per" unit, so for this it would be per second.

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205793570 wrote:I am probably missing a key point from the lectures but I always see that we use a 9.1x10^-31, What does it represent? when do we use exactly?

if I remember correctly I think that is the mass of an electron. this value is also on the constants and equation sheet.

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these are just two different ways to the write the equation but they mean the same. they are just written differently so that one can be used easily for wavelengths and the other for frequency.

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does anyone know if the test is open notes or not?

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I'm still a little confused about quantum numbers. do the numbers just correspond to the electron in the highest orbital? I copied down the chart that dr. Lavelle gave in our notes that shows n=3 and the corresponding boxes with the quantum numbers but I am just not too sure about what these quantum...

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is anyone else having issues with loading the midterm practice problem on respondus? I've tried multiple times but I only see a white screen and in the upper right corner, when I hover over an icon, it says that the site is blocked or something similar to that.

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I think dr. Lavelle mentioned that we won't actually have problems where we need to use the equation but he gave it to us to build a foundation for understanding the concept.

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similar to katrinahuwang_1L, I learned in high school by using this chart: 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p and the arrows will go diagonally from right to left. I'll follow the pattern that the arrow creates while counting the the number of electrons until I reach the needed...

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if a nodal plane is where there is zero electron density, would it still be possible for an electron to appear here for a short amount of time since aren't electrons constantly moving around, so what would prevent it from appearing on these nodal planes?

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I was also quite lost after that lecture. has anyone found any YouTube videos that would go more in depth and explains it a little more?

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I think Dr. Lavelle sent out an email recently saying that the week 4 Wednesday lecture information will not be on the midterms.

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I have never had to remember molar masses of elements for any of my previous chem classes. I believe we should have access to a periodic table during exams so that should not be an issue.

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Usually, I would try to not estimate/round my answers until the end of the problem where I get my final answer. However, sometimes when there are multiple parts, I would apply sig figs at the end of each part.

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Usually, I would try to not estimate/round my answers until the end of the problem where I get my final answer. However, sometimes when there are multiple parts, I would apply sig figs at the end of each part.

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Yes! I think it is a good habit to just double check is equations are balanced before starting an actual problem. It is much better to do so than to realize halfway through the problem that the equation wasn't balanced.

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The actual yield is usually less than the theoretical yield because of different factors during the actual experiment. For example, one common factor that causes an actual yield that is less than the theoretical is that some of the solution sticks to the side of the container.

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I absolutely love rainbow goldfish, especially the green ones haha.

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I've been interested in going into the med-field, specifically to become a pediatrician, but I've been lacking a sense of motivation recently. However, reading your post brought back my hopes and excitements of pursuing this career goal!

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I thought those videos technically don't have a set due date, but they are highly recommended to use because they add onto the topics we are learning about in class.

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After seeing the original post in this thread, I immediately thought to my previous job as a waiter before moving to Westwood! The FDA and local county health department has many regulations in place about how food should be stored, what temperatures it must be heated to, etc. We always had to use ...

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