CHEMISTRY COMMUNITY

Sophia Peavy Lec 1

Yes and we can see in an equation based on the arrow too if it goes in both directions. We discussed that phase changes are always reversible when we do problems with them.

Sophia Peavy Lec 1

Hi it should just be the 8.3145 value typically, but you use any R value that cancels out the other units in your problem.

Sophia Peavy Lec 1

Dr. Lavelle,

Thank you for showing up to each lecture with positive and happy energy. It made my mornings much more bearable and more motivated to pay attention and work hard!

Sophia Peavy Lec 1

Hi! So on the left it is the ln(8) and then one thing to make sure is that your Ea is in the same units as R. After this it should just be cross-dividing and solving for T2.

Sophia Peavy Lec 1

Hi! So to do this question you just plug the Ea into the Arrhenius equation and then you can divide the catalyst solution by the noncatalyzed solution which will give you how many times faster the catalyzed reaction is compared to the noncatalyzed reaction.

Sophia Peavy Lec 1

I dont recall learning this equation, I just figured it out through the practice problems. But I think that you also could derive it if need be, but it isnt really necessary

Sophia Peavy Lec 1

Hi yes that was all right! I conceptualize it by thinking if there are more positions for the molecules like with gas and then liquid then there is higher entropy. Also, increasing molecular complexity directly goes up with entropy.

Sophia Peavy Lec 1

I think there typically is not more than 1 catalyst but it is possible to have 2 that work together. Not sure how to figure out the strength though, interesting question! That definitely wont be on the exam though.

Sophia Peavy Lec 1

^^ most of the practice problems ignore the A from the reaction altogether and therefore just assume that it is equal to 1 so unless given you can essentially just ignore it.

Sophia Peavy Lec 1

Yes that is correct! A positive voltage is needed for E in order for it to be spontaneous and opposite for Gibbs.

Sophia Peavy Lec 1

Yes it is the frequency of the molecules colliding!

Sophia Peavy Lec 1

Hi! So yeah you do the exact same thing as you would do with acidic conditions which is where you get the H+. But you are going to add OH- to both sides so that this H+ will combine with the OH- to form a water molecule and you are left with the OH- molecules on the other side of the equation since ...

Sophia Peavy Lec 1

Hi there I am a bit confused as well. What context did he say that E naught is always 0? I dont think this is possible since this means that there would be no cell potential and no reaction would take place. But I am not sure.

Sophia Peavy Lec 1

Yes, and they will never be in the overall reaction. So it is just something that is needed in the in-between processes to get the final products.

Sophia Peavy Lec 1

Hey yall I was wondering if anyone has some good videos for practicing kinetics problems including the Arrhenius equation, I think I need to watch people work out some problems. Thank you!!

Sophia Peavy Lec 1

No, I think as long as the correct terms cancel out and you are left with the equation that you need it doesn't matter :)

Sophia Peavy Lec 1

In the examples we looked at galvanic cells use spontaneous reactions to generate the current flow whereas with concentration cells have similar compositions of each of the products and solutions and as they reach equilibrium I believe they generate the current of energy.

Sophia Peavy Lec 1

Electrolysis is the process of using energy to drive a nonspontaneous reaction, so I think this would just be used when we want to push a reaction to occur when it wouldn't typically do it on its own (ex maybe the activation energy is too high for the rxn to occur naturally)

Sophia Peavy Lec 1

I think voltage is the same as potential difference since it's like the sum energy of the reaction.

Sophia Peavy Lec 1

I believe they may be referring to any reaction that is not yet in equilibrium? Not sure though what was the context for this?

Sophia Peavy Lec 1

^^ I think we typically find that in this class partial pressure is equated to molarity for gases since it also is relating to its concentration

Sophia Peavy Lec 1

Hi there. So for this problem you don’t need to include the water in balancing the half reaction. You can first balance the half reactions on their own and figure out everything first. Then after this you can add in the waters to balance out the equations and then add H+ to balance out any extra Hs ...

Sophia Peavy Lec 1

Hi y’all I just wanted to confirm the cell diagram. I know that the anode is all the way to the left and is then separated by | but what determines what goes closest to the salt bridge? I know we separate the phases with | I just am not sure when there’s the solution and the other molecules in conta...

Sophia Peavy Lec 1

Omg just realized the person above recommended the same video as me lol, it was really helpful. Also this one below is a bit longer but is very helpful and in depth.

https://youtu.be/YWl4KHsUxuw

Sophia Peavy Lec 1

Hi! This video really helped me out for balancing reactions under acidic or basic conditions which is when we add the water to balance out the equation!

https://youtu.be/N6ivvu6xlog

Sophia Peavy Lec 1

Hi! I struggled with this one too. the equation to find this is e=E0-(RT)/(nF) *lnQ So, you use the molar concentrations to find what Q is and then plug that in to find that part of the equation. To find E0 you would look at the standard reduction potentials page and figure out which part of the rea...

Sophia Peavy Lec 1

Yes, its the generic term for the cells. There are different types that we discussed in class such as those with the salt bridge or the porous disk, but an electrochemical cell is simply the device that can generate electrical energy from the reactions that are occurring naturally.

Sophia Peavy Lec 1

I dont think so, I am pretty sure as long as the temperature change remains 0 then it is isothermal. So while it typically would be a closed system as we have looked at, there can be isothermal systems that are not closed as long as delta t is 0.

Sophia Peavy Lec 1

^^ also make sure that when accounting for the electrons you take the coefficients into account, but for the E0 you simply just use the standard reduction potentials. This got me last time on this problem. The oxidations numbers are only important in this case to calculate the moles of electrons.

Sophia Peavy Lec 1

There also is a resource for oxidation numbers in the book that tells you some basic rules. For example, O2 when attached to a nonmetal will have an oxidation number of -2. From this you can figure out the charge for the other atom in the molecule. Also, from the periodic table we can find some of t...

Sophia Peavy Lec 1

OHH ok that makes so much more sense, I think I got a bit confused with it since I would just assume that Qp was given rather than found with that equation. Thank ya'll so much!!

Sophia Peavy Lec 1

Hey yall, I had a question about the relationship between delta h and qp. I know that we learned that they are equal to each other when there is constant pressure, but I also saw another equation where when pressure and temperature are constant then delta h is equal to delta u plus P delta V, so I w...

Sophia Peavy Lec 1

A follow-up question for this, how can we calculate the number of positions? Do we need to draw out every possible structure or is there a formula that we can use to determine this if we are not given the number of positions?

Sophia Peavy Lec 1

As long as the units cancel out you're good! So definitely just look at those before choosing the R value on the page.

Sophia Peavy Lec 1

If both pressure and volume are constant we just use R right?

CHEMISTRY COMMUNITY

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