CHEMISTRY COMMUNITY

Leila_4G

Also, k is a intensive property, not an extensive property, right?

Leila_4G

And what is the A again?
(I’m sorry I always forget)

Leila_4G

He said he’d send out info today but it’s already 4 pm. Have you guys received anything?

Leila_4G

Same, I’m really nervous I’m going to miss an email and then get an f or something because I missed the time.

Leila_4G

@ Daniel Chen 2L , I am also curious about that... Something else that confused me was when the textbook would say the temperature that did not seem like a standard temp, but then would say what k equals. I'm pretty sure that I should just use the k and note that the temp was only given for context....

Leila_4G

Is there a certain amount within an integer that we should get in order to assume it counts for experimental error and round it?
Like, say on the exam I get n=1.75. Is that close enough to round to 2? If not, what is the general cutoff for being close enough?

Leila_4G

And what is the units for the rate constant of the zero order rxn?

Leila_4G

Also, will we ever get a graph with a curve of lnA/t even if we have the correct order reaction? I thought I saw an example like that in the book but I was confused.

Leila_4G

In what case would we ever get a negative rate constant?

Leila_4G

Hi! Have you heard about the final review that Lyndon and Matt usually do?

Leila_4G

I am having trouble finding the n value in part b. I keep getting 10 or 5. Do you know how to do this part? Thank you!

Leila_4G

Why is the anode on the right? I thought galvanic cells have positive overall cell potentials?

Leila_4G

A positive cell potential means that the cathode is the electrode on the right of the cell diagram. A negative cell potential means that the cathode is the electrode on the left side of the cell diagram. Since the problem states that the cell potential was found to be negative, then this means that...

Leila_4G

I didn't realize that the cell diagram does not represent the order of the molecules in the reaction. But a rule I can follow is that the side being oxidized is the anode, and whatever solid that is on that side should be on the side of the anode, right? And that if there is no solid then the electr...

Leila_4G

Thank you ThomasNguyen_Dis1H! That was really helpful. I was reminded of those two types of cells (galvantic and electrolytic). There is also a concentration cell in which the cell potential is zero because the standard reduction potentials are equal.

Leila_4G

Thank you.
On a related note, why do both the half reactions cell potential of the oxidation of 2Cl- and the reduction of Cl2 equal the same number? In my discussion today we did a problem like that and the cell potentials were not opposite signs of each other.

Leila_4G

Yeah, I am pretty sure we'll be given all those values, we don't need to memorize it.

Leila_4G

My TA talks about the "e-chem series" and how if the value is higher then it has more oxidizing/reducing power, but what is the e-chem series?

Leila_4G

We are never given T so we can't solve the last step for w and therefore q.

Leila_4G

And make sure you're using the same unit for Joules/Kilojoules! :)
The textbook switches it sometimes and it got me a couple times.

Leila_4G

Thank you! This helped so much!

Leila_4G

And to further clarify, standard enthalpy for a reaction and heat needed for that reaction are the same, right? As long as the q is for the same number of moles at the delta H is for.
Because I noticed that standard enthalpy only has the units of kJ (or J). (Not kJ per mol)

Leila_4G

I feel you, it seems like there are so many typos in the textbook I don't really trust the answer key that much.

Leila_4G

Thank you, that helps a lot! :)
But do you know what I mean about how in high school we learned that the entropy of the universe is always increasing? Maybe I misunderstood that when we originally learned that.

Leila_4G

It is because it says the work is done on the system. Therefore the system is gaining that energy and the surroundings are losing it.
For example, when we pump a bike tire, we (surroundings) are doing work on the tire (system), which is why we feel tired. We are losing delta U

Leila_4G

Is heat capacity a state function? I thought that if it relies on the change in heat/transfer of heat then it is not a state function?

Leila_4G

I'm kind of confused, what does -P delta V equal?
Thank you!

Leila_4G

Isn't degeneracy used for the entropy equation (S=kBlnW)?

Leila_4G

Thank you, Ariel! That helped a lot.

Leila_4G

What is a microstate?
(I'm sorry, I don't remember this part of the lecture!)

Leila_4G

Why would entropy decrease in the universe? I thought there was a rule we learned in high school that the entropy of the universe is always increasing.
Also, why would entropy decrease in general?

Leila_4G

Why/when does entropy have a negative value? I thought that entropy only increases? Or is that only for the entire universe?

Leila_4G

This makes me really scared of steam now!

Leila_4G

Do solids and liquids only use C? Or do they use Cv? I'm pretty sure they don't use Cp.

Leila_4G

And -q means heat out of the system and into the surroundings, right?

Leila_4G

Is the table we find this in the textbook or is there a general one online that is the same?

Leila_4G

This confuses me too because its not like it gives off energy to create a bond, right? Unless it is saying it gives off energy to break a bond.

Leila_4G

What are the implications of these reversible/irreversible processes?

Leila_4G

The final vertical pieces of data show the reaction at equilibrium, right?

Leila_4G

This principle describes the movement of the reaction a certain way to make it try to reach equilibrium.

Leila_4G

Since changing temperature is the only thing that affects changing K, it becomes a different reaction, right?

Leila_4G

Similarly, why would adding a halogen be special in shifting/not shifting a reaction a certain way?

Leila_4G

On this note, do you have suggestions on how to do more practice problems that are relevant and give you the answers so you can check?

Leila_4G

@stephaniekim2k , That is a really great way of explaining it, thank you! It helped me a lot!

Leila_4G

Just so I am clear, the positive or negative enthalpy represents the object/solution/system itself either losing or gaining heat, not its surroundings, right?

Leila_4G

Also, I'm not sure about the presence of a salt when making a buffer. Can someone please explain that to me? Thanks!

Leila_4G

Also, I'm forgetting the concentration equation for pKb, can someone help me with that? Thanks!

Leila_4G

Do we exclude the x value even if K is a little bit smaller than 10^-3? Like if 10^3.4?

Leila_4G

Also, how often do the circumstances exist when it fails?

Leila_4G

When it fails, how much does it differ than it is supposed to?

Leila_4G

That's a good question, I've been wondering the same thing! Thank you!

Leila_4G

For not including liquids and solids, what if there is H2O as a gas? When I see that I'm worried that there is a typo.
Also, I've noticed a few typos in the textbook so far about figure numbers which is frustrating.

Leila_4G

It's fine to have a negative pH sometimes, right? I got it once on a homework problem and I was worried I was doing it wrong.

Leila_4G

I had a hard time understanding how the strength of weak acids is determined. Sometimes we solve problems for weak acid solutions, but their pH is about 3 or 4. Are we not able to correlate low pH with strength of acidity?

Leila_4G

Is the pKa value on the same scale as the pH scale?

Leila_4G

From what I understand, pressures can be used with Kc or Kp but concentrations can only be used with Kc. Right?

Leila_4G

Thank you! This is very helpful!

Leila_4G

I don't remember learning this, will it be on the final?

Leila_4G

Ka will always be given, right? We don't have to memorize any of them, right?

Leila_4G

Ka will always be given, right? We don't have to memorize any of them, right?

Leila_4G

Therefore, can only acids be polyprotic?
Because if a base is polyprotic doesn't that mean we are referring to its acidic properties of being able to give off protons so its an acid?

Leila_4G

I'm kind of confused now...bond number (like triple/double/single) matters when dealing with hybridization?

Leila_4G

So, just to be clear, the coordination number is always the same as the areas of high electron population, right?

Leila_4G

Thank you! This is very helpful!

Leila_4G

Thank you all! This is very helpful

Leila_4G

In organic molecules where they don't show the carbon atoms or lone pairs, do we assume that there are lone pairs around Oxygens or hydrogens...?

Leila_4G

What is considered the list of common polyatomic ions?

Leila_4G

I notice that there are not really many review sessions for naming, is it less important you think for the final?

Leila_4G

Thank you guys for all of these tips! I wonder if also reading the book will help!

Leila_4G

Also, I wish the review sessions weren't late on a Friday night, those times are difficult for a commuter student but I have no other choice because I need to get a good grade..

Leila_4G

I'm still confused on how we find out about step up sessions. Is it on chem community?

Leila_4G

It seems like all we need to know for sigma/pi bonds for Test 2 is the definition and properties of sigma/pi bonds and what one/two/three bonds mean, is that right?
Thanks!

Leila_4G

Hi! What's the shape of the AX2E VSEPR formula? I think it is bent or trigonal planar, but I'm not sure.

Leila_4G

Also, what are the angles of AX5E (which I think is a square pyramidal shape)?

Leila_4G

What are the angles of the AX2E VSEPR formula? I think this is either a bent shape or trigonal planar but I'm not sure

Leila_4G

Hi! I think it is less than 90 degrees and 120 degrees.

Leila_4G

Do all molecules use hybridized orbitals?

Leila_4G

The physical length that we show the triple bond does not matter when drawing, correct?

Thanks!

Leila_4G

I'm confused on the bond angle for T-shaped molecules with 2 lone pairs (and 3 bonding pairs)? Is it all less than 90?
Thanks!

Leila_4G

Therefore, less orbital overlap means a weaker bond?
Thanks!

Leila_4G

I'm still kind of confused on what a dipole moment is, can you help clarify?

Leila_4G

So, just to be sure, if it is a nonmetal + alkaline earth metal, it is polar molecule?

Leila_4G

Do we need to know this for test 2?

Leila_4G

Up to what section in the textbook do we need to know for the test?

Leila_4G

From the homework questions, it seems like we do. I'm worried that we do?

Leila_4G

Does anyone happen to know a fun/easy limerick to help memorize these?
Thanks!

Leila_4G

This is really helpful, thank you. I'm also having trouble remembering if the ionic radius trend is different than atomic radius trend?

Leila_4G

Is there a formula we have to remember from the Dipole Moments section? I'm having trouble remembering.

Leila_4G

Will we have to know the actual values of electronegativity to determine the minute differences? I assume probably not..

Leila_4G

Were there any other elements perhaps in the same group way down the periodic table that have this exception other than those 3?

Leila_4G

Daria Azizad 1K wrote:Electronegativity also decreases down the periodic table because as more shells are added, the more distant the positive nucleus is from other electrons it would attract; thus the electrostatic forces of attraction are weaker.

This helps so much! Thank you!

Leila_4G

I don't really understand why elements in group 1 are not highly electronegative? Maybe I don't know the definition of electronegativity.
Also, why does electronegativity increase at you go up the groups?

Leila_4G

So when we draw the orbital configuration, does 4s go in a row below 3d if we are drawing it vertically with the higher energy levels going up?

Leila_4G

This is very helpful! Thank you!
And this is the same equation that Dr. Lavelle talked about how the velocity does not matter as much as the mass because when things are super small the differences in velocity don't make much of a difference?
(Sorry if that was worded very poorly!)

Leila_4G

Hi! I was also wondering when other midterm review sessions will be?

Leila_4G

Also, to what extent do you think we have to know and memorize the configurations? Do we have to be able to recognize each one up to the d orbitals?

Leila_4G

In the 3p subshell, where l=1, does this mean ml=0? Can ml=0?

Leila_4G

Hi! I am struggling a lot with 1D 13 b. How can be find the values of ml for an electron in the 6d subshell?

Leila_4G

So what distance does Δx represent on the electron level? The change in position between the first energy state and the second?

Leila_4G

I still don't understand why delta v is equal to the +/- number attached to the velocity when the velocity is given. It seems like it should be twice the value of the number that is +/-, but my TA told be explicitly that it is not.

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