CHEMISTRY COMMUNITY

Nick Lewis 4F

The rate depends on the slowest step, just like the old phrase your only as strong as your weakest link.

Nick Lewis 4F

Daniel Chen 2L wrote:One of the main things that a catalyst does is change the amount of work that a system does.

Does this have an impact on any of the properties of the other elements involved in the reaction?

Nick Lewis 4F

What is useful about catalysts? Do they lower activation energy or just progress the reaction so it overcomes the activation energy faster?

Nick Lewis 4F

Is one way correct over another? Or are both fine to use where you will get the correct answer either way

Nick Lewis 4F

Hey, just looking back on chem community. Does anyone know what the correct answer was on the final for the question that asked which reaction favored products? It was the last question and had 2 different graphs

Nick Lewis 4F

Why don't we flip the values of standard cell potential for the half reactions when we flip the reaction around to make it oxidation or reduction? I get how to do all the questions and stuff and how to do the calculations but this is something that has not clicked for me conceptually.

Nick Lewis 4F

As we saw on test 2, one of the main things that is tested on concentration cells is the fact that the standard cell potential is always zero. This is something that is worth being noted because it can be used to calculate the cell potential using the nernst equation. I wouldnt be surprised if it ca...

Nick Lewis 4F

If the rate of reaction only depends on how frequently the molecules collide with each other, then what is the point in differentiating zero, first, and second order reactions? My logic here is are these categorizations ways of labelling higher probability zones that they will collide more? Its hard...

Nick Lewis 4F

Does this mean that the Arrhenius equation needs to be used when a catalyst is used and there is a temp change or just if there is a temperature change at all? Also, how does this come into play with a biological example? i.e what does it look like in nature?

Nick Lewis 4F

I think all Dr Lavelle means by this is that a catalyst simply affects the speed of the reaction, not the concentrations of any elements. It reaches the same equilibrium/ end point concentrations, but goes about it in a faster manner

Nick Lewis 4F

Integrated rate laws help you relate the rate law to time in a conceptual way. As shown in the email Lavelle recently sent, there are trends you can remember with the integrated rate laws that result in linear relationships with time

Nick Lewis 4F

Just one quick question to make sure im studying the right information... In the rate law it is written where a is negative and b and c are positive... is this cause reactant concentration goes down while product concentration goes up?

Nick Lewis 4F

What does the electrochemical series look like and how could it be tested?

Nick Lewis 4F

Rust is a natural and pretty go to example of a redox reaction occurring in nature

Nick Lewis 4F

What is the difference between zero, first and second order reactions?

Nick Lewis 4F

I think you should definitely go to Lyndon's review sessions, catch up using only study tools like Khan Academy and just doing as many example problems as you can.Thats all I do and I've always done pretty well above the curve in this class

Nick Lewis 4F

It is the oxidizing agent because it is the one that causes oxidation to happen. It ends up losing electrons by causing another one to gain electrons I think is my understanding of it

Nick Lewis 4F

So does that mean a heavier emphasis will be put on kinetics on the final or is it pretty well rounded?

Nick Lewis 4F

I think its just the more universal syntax but honestly nothing technically wrong with writing it the other way

Nick Lewis 4F

this is currently 6N.1 and I completely agree. Only 1 mole of electrons was transferred and for K I ended up getting e^4.67, or 106.8

Nick Lewis 4F

Can someone explain again why Hydrogen is only capable of +1 ox state?

Nick Lewis 4F

Oxidation is usually exergonic because these reactions release energy, while reduction is usually endergonic because they usually require energy

Nick Lewis 4F

It seems like the oxidation number is just the number of the charge of the ion that is usually formed of that element... is this correct? What is the point in making this distinction?

Nick Lewis 4F

No, I mean there are no other components at work and no matter what you will be able to balance all of these elements in a chemical reaction

Nick Lewis 4F

Balance oxygen by adding h2o, and you balance H+ by adding OH- and can usually play around with the numbers of H and O

Nick Lewis 4F

I don’t think any biological examples were covered distinctly, but I know lavelle incorporates real world examples in almost everything he mentions in lecture. As described before, he talked about organic molucules and natural reactions to demonstrate concepts like heat transfer and enthalpy

Nick Lewis 4F

When did we go over the van hoff equation? Would this be something included on the next test or is it considered a part of the midterm material?

Nick Lewis 4F

Entropy is considered 0 in an isothermal reversible expansion reaction because entropy is a state function and ends in the same final state that it initially starts in.

Nick Lewis 4F

Were no calculations required for the 2nd part? I understood the difference but I went about calculating the entropy different in each part because I knew one was reversible and the other was irreversible. How is it ok to not have to do another calculation when it is specified otherwise in different...

Nick Lewis 4F

How can you differentiate when to use -nRlnV2/V1 versus using -PV? I feel like I always get mixed up when I should use which equation. Any tips for knowing which one to use when?

Nick Lewis 4F

What was the equation that Lavelle shared for calculating the change in mols for a combustion rxn? I dont remember exactly what you're referencing, but it is relatively straight forward to calculate the change in moles in a combustion reaction, just make sure you identify the right stoichiometric c...

Nick Lewis 4F

WIll it always be specified if the item is insulated? Like are we expected to know certain things they reference are insulated? What if its hard to distinguish, or is it pretty clear whether or not its insulated?

Nick Lewis 4F

One thing I am a bit hung up on while studying is why temperature is the only variable that can impact K, wheres vol and pressure changes only impact Q. Can someone break this down a little bit for me?

Nick Lewis 4F

Just to put it out there... do we have to be able to recognize the name of stuff like this? Can't you just derive these equations from simpler equations? Essentially im just a little confused why rearrange the equation and call it something else? I dont really see the purpose in this

Nick Lewis 4F

An isothermal process is a change of system where the temperature remains constant. Therefore, delta U would be equal to 0. I agree with this, for example, in pizza rolls review session they showed how when t = o, delta U = 0, therefore q = -w, which can come in useful knowing some of the types of ...

Nick Lewis 4F

So all energetically favorable reactions are spontaneous but not all spontaneous reactions are energetically favorable?

Nick Lewis 4F

Yes, essentially the third law of thermodynamics is saying that at 0 degrees K, there is no vibrational, rotational, or translational entropy. The only possible entropy results from positional and residual. Thus, knowing the Boltzmann equation would come in handy when asked a question about the res...

Nick Lewis 4F

Does anyone know the point in microstates? I understood lavelle's discussion about this and the Boltzmann equation, but am having trouble understanding its applications. What is the point in making these distinctions?

Nick Lewis 4F

What is the difference in isometric/osochoric? Is this something you think we will need to distinguish between on the midterm?

Nick Lewis 4F

Does anyone know if we are going to have to deal with inconsistent pressure? Are we expected to know how to use calculus in this class?

Nick Lewis 4F

What does it mean to be an "internal system"? What is the distinction between types of systems?

Nick Lewis 4F

Pretty much this is a way of saying that pH + pOH = 14, but it is showing it in terms of the concentrations of [H30+] and [OH-]. I know these equations are usually always given on the equation sheet, so u can deduce subsequent equations from it.

Nick Lewis 4F

By saying it is infinitesimal changes, it is pretty much saying it is continuous. Pretty much it will slowly grow to the equilibrium point, not grow or shrink from point to point

Nick Lewis 4F

I believe Professor Lavelle said something about correlating with size. As the person above me said, complexity (higher mass) would probably mean it has a higher heat capacity in comparison to a simple compound with smaller mass. I think thats an accurate description. Pretty much I think if the com...

Nick Lewis 4F

Are there any other laws we have to remember pertaining to this? I know we went over 3 methods to this, but was this the only one given the name of a law?

Nick Lewis 4F

Is it incorrect to use an equilibrium sign for strong acids/ bases?

Nick Lewis 4F

Lavelle talked about autoprotolysis a lot throughout lectures, so I wouldnt be surprised to see it show up on the test. Definitions above are good, i would say definitely know the equation and be able to explain it, which shouldnt be that hard if you have a rough understanding of what it is.

Nick Lewis 4F

As said above, Lavelle made it clear he was not going over new material. He ran through roughly 3 practice problems, and given that there is no class on monday this was a little review for the test in the coming week. Everything on equilibrium, acids/ bases, and ICE charts. Shouldn't be too bad but ...

Nick Lewis 4F

PV= nRT is an overarching equation that can be manipulated to define a lot of different laws within chemistry, but I think the main thing to notice is the effect temperature has on pressure and volume, and the inversely proportional relationship between p and v

Nick Lewis 4F

What exactly does it mean for the reaction to shift left or to shift right? does it mean there is more products/reactants at equilibrium or it has to produce more in the direction to reach the same ratio at equilibrium again

Nick Lewis 4F

Chatelier's principle can be used to see which direction a reaction will proceed in response to a change in concentration or pressure. For example, if more reactants are added, therefore increasing concentration, Le Chatelier's principle tells us that the reaction will move forward in order to mini...

Nick Lewis 4F

From experience in 14A, the homework problems are really more for your understanding than for credit... just pick any problem relating to something we have gone over and he will accept it, it's more repition that will help you study and do better on the tests.

Nick Lewis 4F

It can get easy to get all your units mixed up, so make sure you are consistenly measuring Kc or Kp depending on the context

Nick Lewis 4F

When they say equilibrium lies to the right, it means that the forward reaction needs to carry out more before it reaches equlibrium, so more product needs to be formed

Nick Lewis 4F

On that note, do you guys think we need to know the isolated equations or is the ideal gas law the only thing we really need to remember?

Nick Lewis 4F

Why in some of the examples in the book (pg. 723) are anion ligands like CN- named cyanido, but then in other complexes named cyano? IF it is overall positively charged is it cyano and if the complex is overall negatively charged is it cyanido? Or is it just IUPAC confusion, and I should only use th...

Nick Lewis 4F

FOr [Fe(NCS)(OH2)5]2+ how do you name iron at the end? I know you use ferrate for a negatively charged complex, but what do you use when it is positively charged?

Nick Lewis 4F

Normally Carbonate is monodentate, because it only has 120 degrees between its Oxygens, so two oxygens cannot bind to the same metal. However, in some cases carbonate bonds to two different metals, making it bidentate. If it is bonding to two different metals, then isn't it not a coordination compo...

Nick Lewis 4F

Does anyone know what Dr. Lavelle means when he says:
atom with lone pair --- spacer atom --- spacer atom --- atom with lone pair
The only part i dont understand is spacer atom. What does spacer atom mean? Conceptually I see why C is the correct answer i am just unfamiliar with this terminology

Nick Lewis 4F

On the exam, are we allowed to write oxalato as (ox) or do we have to say (C2O4)? Can we say (en) or do we have to say NH2CH2CH2NH2? Is one better than the other or are they interchangeable without losing points?

Nick Lewis 4F

For example, on 9C.1, the transition metal is named cobalt for part B, but it is cobaltate for part C. How do you know which name to use? if the complex is anionic, do you name the transition metal + -ate or was this just a coincidence? Sorry, i dont remember what the rule for naming coord. compound...

Nick Lewis 4F

I know usually you can just determine spectator ions based on the ions that are not present in the reaction formula where you only write the ions that contribute to the actual reaction that occurs. Will we have to know how to identify them for the final/ write out these equations?

Nick Lewis 4F

Does anyone have a definite answer about if we need to know a list of strong acids and bases?
I remember we are only going to have to determine the pH of strong acids, but will we be asked to identify/ differentiate strong acids from weak acids

Nick Lewis 4F

I understand Ka and Kb, but what is a conjugate seesaw? How will questions be brought up on this topic on the final?

Nick Lewis 4F

Is it only a stereocenter if all the atoms are different, or can 2 or more atoms be the same?

Nick Lewis 4F

What does an industrial example look like? Does industrial refer to the context of how the compound is applied, or something else? Trying to study and see if this is something i need to study more

Nick Lewis 4F

Can someone explain to my what denticity measures? I have been following pretty closely but the language is getting really complex and I am getting really confused

Nick Lewis 4F

Is H20 amphiprotic?

Nick Lewis 4F

Did Lavelle go over these theories in class? I don’t have any recollection of it and don’t wanna get hit by a curveball on the final. Where do they originate from, how would it be tested , etc.

Nick Lewis 4F

Are the biological implications relevant for this class? I thought Lavelle just likes discussing the implications but it’s not actually necessary to know for the tests. I could be wrong but that was just my understanding up to this point

Nick Lewis 4F

How do these topics come into question on the test? I don’t really understand the concept of naming these things and their application

Nick Lewis 4F

I missed this lecture. What is a coordination compound and what is a ligand? I am so confused it all sounded so complicated and I had to miss lecture so I feel really behind.

Nick Lewis 4F

Is donating a proton really the same as accepting an electron pair? What is the distinction and when does it come into play or are they exactly the same thing just interchangeable terms?

Nick Lewis 4F

Does it matter in what order we draw the atoms in the molecule? I forget what Dr. Lavelle said about structuring our drawing, although I know he said we need to know how to identify the molecules.

Nick Lewis 4F

Does anyone know the shape of a molecule that has 2 bonding pairs of electrons and 3 unbonding pairs of electrons? Just trying to think of different combos that didnt come up during lecture.

Nick Lewis 4F

Yes, i think the terms are interchangeable. Pretty much the cation donates the electrons to the anion that holds all the electrons after and accepts the electrons.

Nick Lewis 4F

Do you have any example questions of how this would be tested? I understand the concepts but dont see how it could be tested on a test

Nick Lewis 4F

Have we gone over sigma and pi bonds yet? Do we have any more information about what exact material will be tested?

Nick Lewis 4F

Essentially, does this mean that boiling points have a direct correlation to electronegativity? I would think that if an atom is more electronegative then there is a stronger bond and thus a higher boiling point.

Nick Lewis 4F

What do sigma bonds look like versus pi ponds? Can you visually differentiate between the two or is it just a convention to describe them?

Nick Lewis 4F

What does hybridization look like? Is it just a way to describe how the electrons are arranged, or do the geometric e- distributions blend together and there a greater region where e- can be located?

Nick Lewis 4F

This is a good question- usually the shorthand convention is to use the last noble gas and then write out the configuration. However, when you first learn them, they usually want to see you write them out all the way. It isn't too difficult and pretty self explanatory.

Nick Lewis 4F

I think Ep is always negative because when 2 molecules interact, it is usually a likely reaction when Ep is negative. It is likely to happen and when they interact, energy is released, hence the negative sign.

Nick Lewis 4F

Isn't there a greater shielding effect because iodine has a larger atomic radius than the other molecules? Im having trouble conceptualizing this becuase I would think F2 would have a stronger interaction because fluorine is the most electronegative atom and I thought they want the electrons the most.

Nick Lewis 4F

Can someone explain how shielding works? I understand the concept as when there are more expanded shells of electrons the electrons are further away and the ones in the furthest shell are not pulled on as much, but is it the idea that the ones closer to the nucleus are "stealing" more of t...

Nick Lewis 4F

If one dipole is induced and the induces another dipole, how does this interaction even begin? I am having trouble rationalizing this conceptually because I don't see how these molecules can induce a dipole when there is not something with a charge to incite it.

Nick Lewis 4F

Does it count as a resonance structure if it isn't the best way of arranging the compound? For example, we went over how to draw N2O at the review session and there were a bunch of different ways, but they weren't necessarily the best. Are resonance structure any variable form, or just variable form...

Nick Lewis 4F

How do you compare the electronegativities of elements across rows/ columns? Like how do you compare oxygen and chlorine when they are in equivalent positions of comparison? IS this something we would have to know how to explain on the midterm?

Nick Lewis 4F

What is the basis of the octet? LIke where does the logic come from and like how do we know some only want 8 when other elements want more or less? I know its the s2 and p6, but why does this mean Be, B can't have 8?

Nick Lewis 4F

Can someone explain why sulfur and those other atoms can take more than 8 electrons? I remember Dr. Lavelle had a good explanation in class but I am having trouble coming up with his explanation while trying to study.

Nick Lewis 4F

I thought we were gonna be given partial credit, but my TA saw one tiny sign mistake in my problem and took away all points for that question (8 POINTS). When I asked him about it he said "you say wrong answer, you get no credit"... anyone else have this problem? Already made sure I switch...

Nick Lewis 4F

Nare Arakelian Dis 3E wrote:Why is 3d at a lower energy level than 4s?

3d is at a lower energy level than 4s because it is at the n = 3 level. At the n = 3 level, there is less energy then the 4s. Dr. Lavelle went over how to determine these quantum numbers in lecture and has shown the differences in energy at each n level.

Nick Lewis 4F

How can they measure the electron affinity? The way I think of it, I thought it was just described as how badly an atom wants to gain an electron. SO it takes less energy to add one as you move across the periodic table cause it gets closer to filling the octet. How can there be a negative energy?

Nick Lewis 4F

I unfortunately had to miss this lecture, but I was reviewing the notes from class and got a little confused when I was looking at this. this is E = q1q2/r. How does one determine the charge of each electron, and how can you experimentally determine the distance between these charges? Just curious b...

Nick Lewis 4F

I'm sure the textbook messed up. The first 2 electrons will occupy the 1s orbital, thus denoted as 1s2. It then follows the sequence of 1s2 2s2 2p6...
It doesn't really get messy in configurations until you reach period 4 where 4s fills before 3d.

Nick Lewis 4F

I think there's a lot of ways you can elaborate on learning in class. What I do is I review my notes, see what resources are online on Dr. Lavelle's website, and then sometimes I will look up topics online and read about them. I will go on youtube and find people that explain concepts more in depth ...

Nick Lewis 4F

I have a general question. The electron density distributions were illustrated for s p and d orbitals. What exactly do these show? For example, p-orbitals show 2 lobes on either side of the nucleus. Can electrons be found anywhere within the lobe on either side, or is it just on the border of these ...

Nick Lewis 4F

What about when there are 2 electons in the s-orbital? Is it easier to remove 1 electron over the other depending on where they are orbiting around the nucleus, or is it just as easy to remove one electron as it is the other? Just wondering if this is relevant because I think it could be interesting...

Nick Lewis 4F

How does linear momentum relate to the De Broglie equation? I know the equation shows that wavelength = planck's constant / momentum, but what exactly does this mean? Does it just mean that an object with higher momentum will have a shorter wavelength? Cause it shows an inversely proportional relati...

Nick Lewis 4F

Isn't spin up and spin down just relative? Couldn't it be that one electron spins to the left and one electron spins to the right? The only thing I am confused about is does this mean that the electrons are spinning in exactly 2 different directions? I'm just having trouble conceptualizing this conc...

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