CHEMISTRY COMMUNITY

Jaci Glassick 2G

In an acidic solution, we use H+ and H2O to balance the half-reaction. First you balance the oxygen using H2O, then hydrogen with H+.
In a basic solution, we use OH- and H2O. I wish I had better advice than this but you kind of just mess with the ratios until all elements balance.

Jaci Glassick 2G

The slope of a 2nd order reaction (1/[A] vs. time) is k. The graph is linear.

Jaci Glassick 2G

I don't think we have gotten any specific information regarding the final or than the fact it is take home, open-book, and going to be a little more straightforward. Lavelle's email last night said that he will be sending us instructions and putting the final questions up on his website soon.

Jaci Glassick 2G

Does anyone have any idea if the step-up sessions and scheduled reviews are still going to take place? Will tomorrows review by Lavelle be bruincasted?

Jaci Glassick 2G

THANK YOU SO SO SO SO MUCH FOR THIS WORKSHEET AND BEING SUCH AN ATTENTIVE UA FOR THESE PAST TWO QUARTER!!!!
That said, is the Friday review still happening? If so, how's that going to work?

Jaci Glassick 2G

According to the solutions manual, n=2 for this problem. I'm not quite sure why you are thinking n should equal 1. You are correct in thinking n=2 (through looking at the half reactions) and the solution manual proves that n indeed is equal to 2.

Jaci Glassick 2G

n is the number of electrons transferred. In order to find n, you have to write the half reactions of the reaction. In part a) of 6.L.1, n is two because 2e- transfer between 2Ce4+ and 2Ce3+ (the half reaction is 2Ce4+ + 2e- === 2Ce3+ which gives an equal charge of +6 on both sides of the half react...

Jaci Glassick 2G

Yep! it is okay to use both as long as you remember the conversion constant involved (lnx=2.303logx).

Jaci Glassick 2G

When balancing in an acidic solution, I believe you use H+ and H2O. In a basic solution, you use OH- and H2O.

Jaci Glassick 2G

Can someone people explain the difference in 1st, 2nd, and 0 order reactions? I understand that you must use different equations when dealing with each, but I'm not sure how to tell the difference between them. Is that information given to you?

Jaci Glassick 2G

The anode is pretty much always going to be on the left side of the salt bridge while the cathode will be on the right.

Jaci Glassick 2G

Log is used in the Nernst equation because log is always used with pH. I believe you can still use ln as long as you remember that ln x= 2.303 log x.

Jaci Glassick 2G

Eo is standard cell potential. It is E at 25C.1atm.1M (standard conditions).

Jaci Glassick 2G

DeltaG is a measure of how much potential a reaction has left to do a net something, so if the reaction is at equilibrium, then no more work can be done and deltaG is 0.

Jaci Glassick 2G

You use Pt when electrons can not be conducted from anode to cathode because there is no metal present. Basically, you use Pt when the cathode and anode is aqueous to aqueous instead of solid to aqueous.

Jaci Glassick 2G

The reaction is favorable when the E cell is positive. In return, a reaction is favorable when deltaG is negative (as when E cell is positive, deltaG is negative).

Jaci Glassick 2G

Although we will be covering further material before the test, Test 2 will only cover the end of thermodynamics and electrochemistry.

Jaci Glassick 2G

My TA said that for the purposes of this class, it is safe to assume that the charge of O2 will always be 2-. As for ozone, I'm pretty sure the charge is 0.

Jaci Glassick 2G

That involves the equations G=RTlnQ and G=RTlnK.

Jaci Glassick 2G

Whenever using the gas constant, you are always trying to match up the units. In the case of G=RTlnK you are always going to use 8.314 J/mol.K because the units match (G is in J/mol, T is in kelvin).

Jaci Glassick 2G

In an isothermal reversible reaction, deltaS total is equal to 0. This means that deltaS surroundings=-deltaS system.
In an isothermal irreversible reaction, deltaS surroundings is equal to 0. This means that deltaS total=deltaS system.
Hope this helps!

Jaci Glassick 2G

I remember it best by thinking of the phase change diagram. There are sloped/diagonal parts and there are horizontal parts. You have to calculate each part separately. Delta Hfus and Delta Hvap are used during those horizontal parts. During the sloped parts, you can used the normal mCdeltaT equation.

Jaci Glassick 2G

There might be some times in which a reversible reaction is not isothermal but I'm pretty sure we'll only be asked about isothermal reversible.

Jaci Glassick 2G

Solids and liquids are excluded when calculating Q and K. Gases and aqueous particles are included.

Jaci Glassick 2G

Basically, the only variables that aren't state functions are w and q. The rest are state functions.

Jaci Glassick 2G

For constant pressure Cv is used and for constant volume Cp is used. My TA kind of mentioned that most of the time you are just going to end up using Cv but they both should work.

Jaci Glassick 2G

In an isolated system, there can be in interaction between the system and its surroundings. In a closed system, there can be interaction with the surroundings.

Jaci Glassick 2G

This is a problem from a review sheet from my TA. Can someone please explain how to do this problem?

Jaci Glassick 2G

I am just wondering when Lydon's review is? In an earlier email, it was on Monday evening from 6-9, but on Lavelle's website and on another email it is on Sunday from 2-5. Just would like some clarification. Thank you!

Jaci Glassick 2G

Your best bet is to look at the equation sheet provided for Test 1 and then see what equations are not there.

Jaci Glassick 2G

I saw that Lyndon's review session is Sunday, but did he make a review sheet? If so what is the key word to search it up? Thank you so much!

Jaci Glassick 2G

I believe there are some problems from 4D and 4E that we can do (maybe some from 4C). Hope this helps!

Jaci Glassick 2G

The equilibrium constant will change with temperature. If the reaction is exothermic (releases heat), your constant will decrease. If the reaction is endothermic (absorbs heat), your constant will increase.

Jaci Glassick 2G

So far, I believe we have covered 4C4, 4C5, 4D3, 4D4, 4D5, and 4E. I hope with helps!

Jaci Glassick 2G

They are basically the same thing. I would just stick with whatever the problem gives you/asks you to answer in. I don't think it matters too much.

Jaci Glassick 2G

I believe that enthalpy should always be written in kJ/mol, but sometimes the textbook writes it in terms of just kJ. I would jut stick to kJ/mol.

Jaci Glassick 2G

If the initial concentration (the I column) is 0, then the E column will end up either being x or -x. If the initial concentration is not 0 (lets say it is "a"), the E column will end up being either a-x or a+x.

Jaci Glassick 2G

I did this problem kinda backwards:
I took the -log of 1.5 to get pH. From there, I found pOH and then found the OH- concentration from that.
I know that probably wasn't the fastest way to do this problem, but it worked in my brain.

Jaci Glassick 2G

You would have to use the ideal gas law (PV=nRT) to calculate P using the other given values.

Jaci Glassick 2G

Since you do not use solids and liquids in finding the k constant, you do not include them in the ICE table. For example, in acid and base equilibrium problems, we do not put water in the ICE table.

Jaci Glassick 2G

Can someone walk me through this problem? I understand how to find the molar concentration of Ba(OH)2 and how to set up the ICE table, but I'm stuck past that. There is no Ka or Kb value. Calculate the molar concentration of Ba(OH)2 and the molar concentrations of Ba2+, OH-, and H3O+ in a solution t...

Jaci Glassick 2G

K is the equilibrium constants. Kc, Kp, Kw are just different "types"/"ways" of finding K. With Kc, you use concentrations of the products and reactants (Kc=P/R). With Kp, you use partial pressures (Kp=Pp/Pr).

Jaci Glassick 2G

I don't think so. It is probably best to review/redo the homework problems on the syllabus.

Jaci Glassick 2G

Both. They are the same thing.

Jaci Glassick 2G

Use the information in Table 5G.2 to determine the value of K at 300 K for the reaction 2BrCl(g) + H2(g) = Br2(g) + 2HCl(g). Can someone please explain how to do this problem for me? I understand that K=P/R, but I don't understand how to come up with the numerical value for K with the information gi...

Jaci Glassick 2G

No, like any other reaction. There are times in which the reaction is at equilibrium and times in which it is not. However Kw of an acid-base reaction at 25 C, is always 1x10^-14. That is constant when the reaction is at equilibrium.

Jaci Glassick 2G

Both can be used. Kc can be used when dealing with concentrations while Kp can be used when dealing with partial pressures. I believe the values will be the same.

Jaci Glassick 2G

Kc occurs when the reaction is at equilibrium. Q is used at any other time during the reaction.

Jaci Glassick 2G

I know this is a bit away, but does anyone what topics will be covered on Test 1? Thank you!

Jaci Glassick 2G

Lavelle did a problem similar to this one in lecture on Friday. In part c, It is best to set up a type of table and then solve the problem. I'm going to attach a picture of the problem to this. Hope it helps!

Jaci Glassick 2G

Ideal gases usually occur when temperature is higher and pressure is lower. The ideal gas law equation is PV=nRT. P is pressure, V is volume, n is the number of moles of gas, R is the universal gas constant, and T is temperature.

Jaci Glassick 2G

Does anyone have any good resources on coordination compounds (other than the textbook)? Like video/online worksheets/etc. I'm slightly confused on the topic.
Thank you!

Jaci Glassick 2G

How do you find with base is stronger? How do you find which acid is stronger?

Jaci Glassick 2G

Decide whether an aqueous solution of each of the following salts has a pH equal to, less than, or greater than 7.
a)NH4Br b)Na2CO3 c)KF d)KBr e)AlCl3 f)Cu(NO3)2

How do I find the pH of the salts? Thank you!

Jaci Glassick 2G

Here are my best tips: -I know everyone drinks a ton of caffeine on finals week to stay up and get things done, but that is actually not very good for you. Caffeine raises your heart rate, therefore raising your blood pressure and putting physical stress on your body. -Treat your body well: eat well...

Jaci Glassick 2G

At the end of the class (after the final and everything), Lavelle will look at the class average and adjust grades based on that. The syllabus goes into more depth about this.

Jaci Glassick 2G

Does anyone know if there will be a curve on the final? There is no curve on the final. At the end of the quarter, the points we have acquired throughout the quarter will be given a grade. Lavelle takes the average points earned and assigns them grades. The final is 180 points out of a total of 500...

Jaci Glassick 2G

VLi_1L wrote:Will there be a curve on the final?

There is no curve on the final. At the end of the quarter, the points we have acquired throughout the quarter will be given a grade. Lavelle takes the average points earned and assigns them grades.

Jaci Glassick 2G

I'm assuming we will get them back in discussion this week. If your discussion has been postponed/cancelled, I would assume you will get it back next week.

Jaci Glassick 2G

I would read all the sections listed with the homework on the syllabus. This helps get a better idea of what will be on the final. Hope this helps!

Jaci Glassick 2G

Which of the following isomers of diaminobenzene can form chelating complexes? Explain your reasoning.

I'm slightly confused by this. Can someone please explain this to me? Thank you!

Jaci Glassick 2G

This question asks: "There are three isomers of C6H4Cl2 which differ in the relative positions of the chlorine atoms on the benzene ring. a) Which of the three forms are polar? b) Which has the has the largest dipole moment?" Can someone please help me out with this question? Sorry I could...

Jaci Glassick 2G

Yes. Any time pi bonds are involved the molecule cannot rotate. The same is true for triple bonds (which hold two pi bonds).

Jaci Glassick 2G

A is the central atom. X represents the bonded atoms. E represents the lone pairs. Take for example SF4: The VSEPR formula notation for this molecule would be AX4E because sulfur is the central atom (A), the four fluorines are the bonded atoms atoms (X4), and finally the sulfur has one pair of lone ...

Jaci Glassick 2G

This is what my TA sent out on a review sheet:
Topics to study: Polarity, Intermolecular forces (induced dipole – induced dipole, dipole-dipole, H-Bond, ionic), Shapes of Molecule (VSEPR, geometry, bond angles), Types of bonds

Jaci Glassick 2G

A molecule is linear if it has two bonded atoms and the central atom has no lone pairs. If the central atom has lone pairs, then the molecule will be bent, not linear. Hope this helps!

Jaci Glassick 2G

SCl4 has the seesaw shape that Dr. Lavelle talked about in class today (I also believe this is known as a trigonal bipyramidal but I might be wrong with that). ICl4 is square planar. All four bonded atoms are 90 degrees from the central atoms.

Jaci Glassick 2G

Test 2 is everything we covered since the midterm. This would include dipole moments, shape, VSEPR, etc.

Jaci Glassick 2G

A is the central atom. X represents the bonded atoms. E represents the lone pairs. Take for example SF4: The VSEPR formula notation for this molecule would be AX4E because sulfur is the central atom (A), the four fluorines are the bonded atoms atoms (X4), and finally the sulfur has one pair of lone ...

Jaci Glassick 2G

I have been told that everything that we have learned that wasn't on the midterm will be on test 2. So, yes, I believe this will be on test 2.

Jaci Glassick 2G

How are you guys studying for the test next week? I don’t really know where to start.

Jaci Glassick 2G

As of right now, shape of the Lewis structure doesn't matter. As we get further along in the quarter, it will matter.

Jaci Glassick 2G

In the first equation, you count the number of actual bonds (so for a double bond, you would count 2 bonds so you plug 2 in for B). In the second, B is the number of electrons shared by the bonds (a double bond shared 4 electrons, so you plug 4 into B). I hope this helps!

Jaci Glassick 2G

"Each test and exam has a total score but is not assigned a grade. Only at the end of the class when the class average score (out of 500 points) is known are final grades assigned. This class does not use a curve. Group learning (Chemistry Community, Study Groups, Peer Learning, etc.) is encour...

Jaci Glassick 2G

I'm not exactly sure. My TA hasn't given us any practice problems concerning this, so I don't think so.

Jaci Glassick 2G

https://socratic.org/questions/what-tre ... ow-on-the-
Electronegativity increases across the period and decreases down the group.

Jaci Glassick 2G

The negative charge would be on the oxygen. Oxygen is more electronegative than nitrogen so its gets the charge.

Jaci Glassick 2G

I would watch the module videos. Hope this helps!

Jaci Glassick 2G

I'm not exactly sure but I think the B stands for number of bonds, not the bond length. But when in doubt, just stick with the equation Dr. Lavelle gave us. Hope this helps!

Jaci Glassick 2G

In this homework question, we have to draw the Lewis dot structures for a series of molecules. All parts of the problem give out the written name for the molecule (ex: periodate ion, hydrogen phosphate ion, caloric acid, arsenate ion). Are we suppose to know how to get the formula from looking at th...

Jaci Glassick 2G

In homework question 2B3, we are asked to draw the Lewis structures for a series of molecules. In part d, we are asked to draw a Lewis structure for BrF3. I am confused on how this structure ends up looking. Please help! Thank you!

Jaci Glassick 2G

Does anyone know if we will be needing any testing materials for the midterm? Just wanting to be prepared. Thank you!
Also, where can we find the locations for the midterm?

Jaci Glassick 2G

Like the other reply said, I’ve been doing the homework problems. I’ve also been watching and doing the assessments for the modules on Lavelle’s website. If you have any questions, it’s always a good idea to talk to your TA. Hope this helps!

Jaci Glassick 2G

http://hyperphysics.phy-astr.gsu.edu/hb ... rfill.html

The first diagram on this page helped me a lot with figuring out the order of e- configurations and their energies.

Jaci Glassick 2G

The number of valence electrons is equal to the main-group number. Hydrogen is in group 1 and has one valence electron. Oxygen is in group 6 and has 6 valence electrons.

Jaci Glassick 2G

How do we know when to write electron configurations with the noble gas abbreviation or when to write the whole thing out? Will we ever need to write the whole thing out or can we always use the noble gas abbreviation? I don't want to get points marked off on homework or on a midterm/test?

Jaci Glassick 2G

I just got out of lecture. Lavelle said that certain atoms can break the octane rule. P, Cl, and S can accommodate more than 8 valence electrons. Atoms in period 3 or higher have higher d-orbitals (I'm literally coping my notes so if this is really brief that is why).

Jaci Glassick 2G

I believe you have to post five times every week in order to get the points. Extra posts from previous weeks do not count toward your weekly minimum.

Jaci Glassick 2G

There is one orbital in an s subshell (l = 0), three orbitals in a p subshell (l = 1), and five orbitals in a d subshell (l = 2).

Jaci Glassick 2G

Like mentioned before, I would ask/email your TA. If there is still a problem, you can get one in the UCLA store. Mine was about $17.

Jaci Glassick 2G

In homework question 1F1, we are asked to to arrange elements in decreasing order of atom radius. I know there is a way to find radius using the periodic table (atomic radius increases as you go down the table and decreases as you go right). Is there a better way to find atomic radius?

Jaci Glassick 2G

Jumping from n=1 to n=2 increases the number of shells you have in the atom. Therefore, n increases. The radius of the atom also increases. I believe both l and energy also increases. Hope this helped!

Jaci Glassick 2G

I’m confused by this problem and how to approach it. And help would be awesome! 1E.9 Of the following sets of four quantum numbers {n, l, ml, ms}, identify the ones that are forbidden for an electron in an atom and explain why they are invalid: (a) {4, 2, −1, +1/2} (b) {5, 0,−1,+1/2} (c) {4, 4, −1,+...

Jaci Glassick 2G

1 Electron volt (eV) = 1.602176565 x 10^-19 joules (J). Therefore 1 keV is equal to 1.602176565 x 10^-16 joules. I'm not sure what units the question should be answered in though. I hope this at least helped a little.

Jaci Glassick 2G

All you need for the test is a pen and a scientific calculator. Constants and a periodic table will be provided.

Jaci Glassick 2G

What did you guys get for the balanced equation in H21? I just spent a while on it, though I finally balanced the equation and then realized I was off by one oxygen. Thank you!

Jaci Glassick 2G

The syllabus and testing schedule doesn’t say anything about needing a blue book or scantron but I would have one just in case. I’m going to shoot an email to my TA just to confirm though.

Jaci Glassick 2G

The syllabus and testing schedule doesn’t say anything about needing a blue book or scantron but I would have one just in case. I’m going to shoot an email to my TA just to confirm though.

Jaci Glassick 2G

Do you guy know when the “week” starts? For instance, if I had posted something yesterday (Sunday Oct 6th), shout the post be given credit for Week 1 or Week 2?

Jaci Glassick 2G

Avogadro's number is 6.022*10^23 (not -23). You use the number when converting moles to molecules/atoms.

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