CHEMISTRY COMMUNITY

Kallista McCarty 1C

Are the answers for this worksheet going to be posted soon?

Kallista McCarty 1C

The oxidizing agent is the one that is reduced and the reducing agent is the one that is oxidized!

Kallista McCarty 1C

I don't think it is going to be very strict, so you can probably use any resource that you have available!

Kallista McCarty 1C

I believe it is used to calculate the activation energy!

Kallista McCarty 1C

We are only using the pre equilibrium method!

Kallista McCarty 1C

Br is not a conducting solid, so Pt needs to be added!

Kallista McCarty 1C

Activation energy is the minimum amount of energy needed for a reaction to take place

Kallista McCarty 1C

An increase in temperature leads to an increase in reaction rate. A decrease in temperature results in a slower reaction rate

Kallista McCarty 1C

I am not sure about this either. Hopefully he sends out an email update soon!

Kallista McCarty 1C

I think that it will just be posted on his website and we will have until the end of the quarter (Friday night maybe?) to complete it. I don't think were going to have a set window anymore since it is so hard not being on campus. Im sure he will give us more information soon!

Kallista McCarty 1C

Brian J Cheng 1I wrote:
Kallista McCarty 1C wrote:I was not able to make it to lecture on Friday, can someone explain what was covered?

If you would like some notes from that lecture, reply with your email and I can send them over :)

Thank you so much! My email is kallistamccarty@gmail.com

Kallista McCarty 1C

K is greater than 1 if Ecell is greater than 0. K is less than 1 if Ecell is less than 0

Kallista McCarty 1C

Lavelle said that we only need to know the pre equilibrium approach so there is nothing you have to know about steady state. He said it is discussed in the textbook if you wanted to look at it, but it is not required. You get the same answer from both approaches

Kallista McCarty 1C

I think the TAs made the final for 14A, but my TA said that Lavelle made the midterm for 14B so he will probably make the final as well

Kallista McCarty 1C

Nitric oxide (NO) is the only catalyst. The O2 is just a reactant

Kallista McCarty 1C

I was not able to make it to lecture on Friday, can someone explain what was covered?

Kallista McCarty 1C

I was not able to make it to lecture on Friday, can someone explain what was covered?

Kallista McCarty 1C

Yes! Elements that are reduced are considered the oxidizing agent and elements that are oxidized are considered the reducing agent. I remember them as opposites of each other

Kallista McCarty 1C

R and F are both constants that are given on the equation sheet. T is the temperature. n is the number of electrons transferred (determined by balancing the half reactions)

Kallista McCarty 1C

We normally get them back the following week in discussion

Kallista McCarty 1C

You should look at the oxidation states or overall charge of the molecule to determine which is being oxidized or reduced

Kallista McCarty 1C

The solids should be on the outside of the cell diagram. The anode goes on the left and the cathode goes on the right normally

Kallista McCarty 1C

n is the number of electrons transferred. Once you balance the half reactions, the number of electrons transferred are equal to each other because they cancel out when you combine the two half reactions to create the full reaction.

Kallista McCarty 1C

There are no official review sessions, but the step up sessions in cover are helpful to review/clarify new information

Kallista McCarty 1C

For the electrochemistry section, n represents the number of electrons transferred. You can find this by balancing the half reactions.

Kallista McCarty 1C

I think the most common will be ∆G = -nFE˚ which is also equal to the maximum work

Kallista McCarty 1C

It uses electron transfer to drive non-spontaneous (unfavorable) redox reactions

Kallista McCarty 1C

It will cover the rest of thermodynamics that was not on the midterm and all of electrochemistry!

Kallista McCarty 1C

the anode is being oxidized (remember this because they both start with vowels) and the cathode is being reduced. Typically the anode is on the left and the cathode is on the right in cell diagrams!

Kallista McCarty 1C

Lavelle has some practice questions posted on sapling learning that might be helpful!

Kallista McCarty 1C

Liquid mercury is able to conduct heat on its own!

Kallista McCarty 1C

n is the number of electrons that are being transferred in the redox reaction. You find this number after balancing the equation.

Kallista McCarty 1C

I would focus on the electrochemistry section (outline 5) because that is mainly what the test next week will cover

Kallista McCarty 1C

It is intensive because it is measured under standard conditions

Kallista McCarty 1C

We talked a lot about the Nernst equation and the different forms of the equation that you can use!

Kallista McCarty 1C

Test 2 will cover the rest of thermodynamics (things that were not on the midterm) and electrochemistry.

Kallista McCarty 1C

I would focus mainly on outline 5 this week!

Kallista McCarty 1C

I think the only one that we need to be able to derive is the Vant Hoff equation! Everything else should be given on the equation sheet (just make sure you can recognize what each one is)!

Kallista McCarty 1C

It breaks it down so you can easily see what is being oxidized and what is being reduced!

Kallista McCarty 1C

At a step up session they gave a couple rules for oxidation numbers and using them to balance redox reactions. 1. free elements have an oxidation number of 0 (ex. Cu) 2. in monoatomic ions, oxidation number is equal to its charge (ex. Na+ has a +1 charge) 3. oxygen is usually -2 4. hydrogen is +1 5....

Kallista McCarty 1C

Since it is an exothermic reaction, when heat is increased K is decreased and the reverse reaction is favored

Kallista McCarty 1C

Test 2 starts on Tuesday of week 9 (it got moved from the scheduled week 8) and covers the rest of thermodynamics (Gibbs free energy) and the whole electrochemistry outline

Kallista McCarty 1C

The naught symbolizes standard temperature and pressure (STP)

Kallista McCarty 1C

It is based on electron transfer. I remember it by "OILRIG" Oxidation is losing e- and reduction is gaining e-

Kallista McCarty 1C

Negative is spontaneous (exothermic) and positive is not spontaneous (endothermic)

Kallista McCarty 1C

The reducing agent causes the reduction, so it is oxidized. The oxidizing agent causes the oxidizing, so it is reduced.

Kallista McCarty 1C

I have heard that it is doable to take those courses together!

Kallista McCarty 1C

I think you use the initial!

Kallista McCarty 1C

yes you can!

Kallista McCarty 1C

I'm not sure if there is an official "curve" but all you need is a 50% overall in the class to pass with a C

Kallista McCarty 1C

You use gaseous and aqueous! You don't put in solids or liquids

Kallista McCarty 1C

Isobaric is constant temperature!

Kallista McCarty 1C

The m refers to molar in this problem!

Kallista McCarty 1C

The midterm is Wednesday from 6-8. You can find your exact location depending on which lecture you are in and your last name on Lavelle's website. There is no lecture that day, but there is a small Q&A review session with a couple TAs during normal lecture time if you have last minute questions!

Kallista McCarty 1C

You can do any problems for this week! The most recent outline that we covered in class was thermodynamics, but you can turn in any problems as long as they are not ones that you have previously turned in!

Kallista McCarty 1C

You should be able to tell given the context of the problem!

Kallista McCarty 1C

A reaction is spontaneous when delta G is negative, so by setting it to zero we were able to find the value and then determine the answer as "above 333K"

Kallista McCarty 1C

Irreversible occurs under a constant pressure and reversible occurs under changing pressures.

Kallista McCarty 1C

Everything that was covered up to the end of today's lecture will be included on the midterm!

Kallista McCarty 1C

Isothermal means that there is a constant temperature and that delta U is also equal to 0

Kallista McCarty 1C

You need a 50% to pass the class with a C-. The other letter grades are determined by the class average.

Kallista McCarty 1C

You can find all the equations that we will be given on Lavelle's website on the constant and equations sheet! It is good to look at it to familiarize yourself with the ones that you'll need!

Kallista McCarty 1C

I think it was changed to Sunday because there were a lot of students who could not go Monday due to the LS30B midterm

Kallista McCarty 1C

The midterm will cover everything until the end of the thermodynamics outline! He should finish lecturing on it this week

Kallista McCarty 1C

Heat can be transferred with the surroundings in a closed system but matter cannot. Neither can be transferred with the surroundings in an isolated system.

Kallista McCarty 1C

for anyone that's been, have you found them helpful/how is the pace of the step-up sessions I go to Jonathan's sessions and I find them extremely helpful! He goes over homework and old test questions and explains the important concepts/equations from lecture and the different contexts that they can...

Kallista McCarty 1C

Lavelle does not give out distribution curves for his test so it is hard to see how you compare

Kallista McCarty 1C

Can someone explain question 5 from the test (the pKa of triethylamine cation is 11.04. A 0.2M solution or triethylamine was made to use as a weak base in the synthesis of a new pharmaceutical. What is the pH of this solution at equilibrium?)

Kallista McCarty 1C

Can someone explain question 5 from the test (the pKa of triethylamine cation is 11.04. A 0.2M solution or triethylamine was made to use as a weak base in the synthesis of a new pharmaceutical. What is the pH of this solution at equilibrium?)

Kallista McCarty 1C

You should use J or kJ!

Kallista McCarty 1C

qv is constant volume and qp is constant pressure

Kallista McCarty 1C

Can someone explain problem 1 a) calculate the concentration of each species at equilibrium?

Kallista McCarty 1C

The pH is 2.92, so the H+ concentration is 10^-2.92 = 1.20 x 10^-3. The pOH is 14-2.92=11.08. The OH- concentration is 10^-11.08 = 8.32 x 10^-12. The Ka is equal to the H+ concentration which is 1.20 x 10^-3. The percent ionization is (1.20 x 10^-3)/(0.010) x 100% = 12%.

Kallista McCarty 1C

I believe it should be kJ/mol, but my TA has used just kJ when writing out the problem and then just inserted kJ/mol at the end. I think it is just a convenience thing!

Kallista McCarty 1C

qp just shows constant pressure and qv shows constant volume.

Kallista McCarty 1C

It will only focus on the material covered in the weeks after the midterm! There won't be any content from before that on the second test

Kallista McCarty 1C

Catalysts are used to speed up reactions, but they do not have an effect on the equilibrium constant!

Kallista McCarty 1C

You add the enthalpies since they are state functions!

Kallista McCarty 1C

Yes, if no temperature is stated you can assume 25 Celsius to solve!

Kallista McCarty 1C

When K is smaller than 10^-3!

Kallista McCarty 1C

Ka = 10^-pKa
Kb = 10^-pKb

Kallista McCarty 1C

You approximate if K is smaller than 10^-3

Kallista McCarty 1C

The UA's typically will put together a worksheet and post it on here, but Lavelle does not give one out.

Kallista McCarty 1C

The R value will be given on the constant and equations sheet on the test! I know that there are different units that you use depending on the question, but they will both be given

Kallista McCarty 1C

I don't think Lavelle has ever discussed this in lecture, so we won't be asked to use it on the test!

Kallista McCarty 1C

There is a workshop session from 6-8 and drop ins from 8-9, but it does not say who is holding them.

Kallista McCarty 1C

If K is smaller than 10^-3 then you can use the approximation method Lavelle taught us in lecture!

Kallista McCarty 1C

Kw is measured at 25 degrees celsius!

Kallista McCarty 1C

Kw is always equal to 1.0 x 10^-14 at 25 degrees celsius!

Kallista McCarty 1C

This is irrelevant to the stated question, but does anyone know if we can still turn in chemical equilibrium hw questions for week 2? Or does it have to be acids and bases? Since we still covered chemical equilibrium this week, you can turn in problems from that section as long as they are differen...

Kallista McCarty 1C

Kristina Rizo 2K wrote:I thought Kp was used for gas only? Can someone clarify this please.

Kp is used for gases to determine partial pressures! Kc is used for concentrations and Ka and Kb are for acids and bases.

Kallista McCarty 1C

There isn't one given out, but it is good to base your studying on the learning outcomes for the sections.

Kallista McCarty 1C

When Q=K the reaction is at equilibrium. When Q<K the forward reaction is favored and when Q>K the reverse reaction is favored.

Kallista McCarty 1C

Since K is a constant it does not have units associated with it!

Kallista McCarty 1C

You can do homework on chemical equilibria or acids and bases. Just make sure it is different problems than the ones that you did last week!

Kallista McCarty 1C

The principle works to minimize the change on the reaction by shifting the direction that the reaction takes place in order to maintain equilibrium.

Kallista McCarty 1C

I think it will be on chemical equilibria and acids and bases! I find it helpful to go to the peer learning sessions in Covel because they typically cover the test topics!

Kallista McCarty 1C

I think you would convert one to the other! Lavelle gave us the equation PV=nRT for this! concentration x RT is the pressure.

Kallista McCarty 1C

You should be able to tell based on the question that is being asked!

Kallista McCarty 1C

Q is the reaction quotient, so you use it to compare to equilibrium. You can use it to study biological systems like rivers when you do not know which way the reaction is occurring. If Q<K the forward reaction is favored and if Q>K then the reverse reaction is favored.

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