CHEMISTRY COMMUNITY

Rita Chen 1B

I think it can be added to any step, but only adding it to the slow step will really change the rate of the reaction. It will both affect the activation energy barrier, but only the one in the slow step will make a difference in the rate because that is the rate determining step.

Rita Chen 1B

I think it would be given because he didn't really say we really needed to know it?

Rita Chen 1B

I think a catalytic converter is used to convert toxic cases like carbon monoxide to something less toxic and is used by coating an exhaust engine with a catalytic converter (I think like platinum?) Can someone confirm

Rita Chen 1B

I think only 7 classrooms are equipped with Bruincast, so not sure if that is an option. I think that the most liekly option is to use zoom and have online classes instead.

Rita Chen 1B

I think Lyndon posted a review called "endgame"

Rita Chen 1B

I had the same question, but I think it would be given to us. Maybe use the one with the solid substance?

Rita Chen 1B

I don’t think spectator ions are included

Rita Chen 1B

I think you find the amount of electrons transferred in the balanced reaction. So it is the number of electrons that eventually cancels out.

Rita Chen 1B

How can I tell whether a metal ion or H2O is reduced for electrolysis?

Rita Chen 1B

Predict the potential of each of the following cells:
(a) Pt(s) | H2(g, 1.0 bar) | HCl(aq, 0.075 mol?L21) || HCl(aq, 1.0 mol?L21) | H2(g, 1.0 bar) | Pt(s).
How do you find the half reactions for this problem?

Rita Chen 1B

Is the only difference between balancing basic and acidic reactions whether you add H+ or OH? Also, do you guys have any tips for balancing? Hi Rita, From what I understand, that is the most important difference between the two! I spoke with Matthew Tran, a UA, regarding balancing tips. I thought h...

Rita Chen 1B

Does this mean that during the same reaction, it can be reduced and oxidized (some will get reduced and some will get oxidized?)

Rita Chen 1B

Is the only difference between balancing basic and acidic reactions whether you add H+ or OH?

Also, do you guys have any tips for balancing?

Rita Chen 1B

https://www.google.com/search?q=balanci ... WPtb_wCQ32

I found this video really helpful!

Rita Chen 1B

Maybe it's talking about delta G, which uses RT lnQ, which may depend on pressures?

Rita Chen 1B

I think we can use it to determine the concentration of reactants at a certain point in reaction.

Rita Chen 1B

Is it possible to have more than 2 galvanic cells together? How would that work?

Rita Chen 1B

I was wondering the same thing. I know that if the reaction is spontaneous and delta G is negative, the E must be positive because of Nernst equation. But I am not sure for if E cell < Estandard Cell.

Rita Chen 1B

I think it depends on the reaction? I could be wrong, but in Dr. Lavelle's example today, the increasing in Mn concentration, caused the forward reaction to be favored, making E increase since the E standard was positive. I think it depends what you increase in concentration.

Rita Chen 1B

I think it just means that the potential difference is the amount of work energy needed to be able to take one electric charge from one place to another.

Rita Chen 1B

We are supposed to find the oxidizing agent/reducing agent of: Cl2(g) --> HClO (aq) +Cl2 (g)

My question is, conceptually, how can something be both the oxidizing and reducing agent?

Rita Chen 1B

When would I use nRln(V2/V1) and when would i use nCpln(T2/T1)? If the pressure is constant and the volume changes, the temperature changes too, so shouldn't both equations be able to be used?

Rita Chen 1B

In the question, how would you approach it? What would you try to solve for first?

Rita Chen 1B

Why is it P1/P2 for delta S and V2/V1?

Rita Chen 1B

Is the only time we need to differentiate between reversible and irreversible when calculating work with: eversible: - nRT ln (v1/v2) and -Pext ΔV and when calculating delta S?

Rita Chen 1B

When is work negative?

Rita Chen 1B

When will I need to factor in both q and w? I’m a little confused.

Rita Chen 1B

Does increasing the temperature always change the entropy of the surroundings?

Rita Chen 1B

In Dr. Lavelle's lecture, he stated that phase changes have entropy changes. Can someone explain why?

Rita Chen 1B

In Dr. Lavelle's lecture, can someone explain why if delta U is 0, why the gas expands?

Rita Chen 1B

Can someone explain spontaneous vs favorable more? I feel like it's often used very interchangeably.

Rita Chen 1B

Are we going to be able to know if a reaction is exothermic or endothermic if the delta H isn't given? If so, how?

Rita Chen 1B

How about at bar because they are very similar?

Rita Chen 1B

What will the midterm cover?

Rita Chen 1B

Will the enthalpies of formation always be given to us if we need it on the test?

Rita Chen 1B

How can we tell which one is which? Like does an insulated water bottle count as isolated?

Rita Chen 1B

Can someone simply explain ∆H and ∆U for me?

Rita Chen 1B

How do we calculate the pH of 0.055 M AlCl3 (aq)?

Rita Chen 1B

Write (a) the chemical equation for the proton transfer equilibrium in water and the corresponding expression for Ka and (b) the chemical equation for the proton transfer equilibrium of the conjugate base and the corresponding expression for Kb for each of the following weak acids: i) HClO2 ii) HCN ...

Rita Chen 1B

But what if the Kc and K are different? Will we usually be given K or Kc depending on which one we use?

Rita Chen 1B

Do we need to know how to convert it? If so, how?

Rita Chen 1B

So when do we use K and when do we use Kc? When will we need to convert and how do we convert it?

Rita Chen 1B

Whats the difference between Kc and K?

Rita Chen 1B

Definitely try to memorize it. I think doing more practice problems really helps you with that!

Rita Chen 1B

I think that the stronger the acid or base, the weaker the conjugate base or acid. So I think you are supposed to use the pKa to determine how strong it is and then compare its conjugate base or acid to the rest.

Rita Chen 1B

6C.5 Write the chemical formula for the conjugate base of formic acid, HCOOH and calculate its pKb from the pKa of formic acid (see Table 6C.1).

6C.9 Use data from Tables 6C.1 and 6C.2 to place the following
bases in order of increasing strength: F2, NH , CH CO 2, C H N
(pyridine).

Rita Chen 1B

In something like N2 + 3H2 —> 2NH3, if we increased N2, does it affect H2 as well?

Rita Chen 1B

I think one thing is that the activity of a solid or liquid is equal to 1, so it doesn’t affect the K constant. Also in terms of solids, it is not dissolved, so would not have a concentration and I think something similar can be said with liquids as well.

Rita Chen 1B

How do we know when something is in dynamic equilibrium?

Rita Chen 1B

At what point should we put the single arrow and not the double arrow?

Rita Chen 1B

Is Keq the same as Kc?
When do we use which?

Rita Chen 1B

I think simply it’s because the inside doesn’t change so the products and reactants don’t change so the K is still the same.

Rita Chen 1B

I believe so. I think it’s also important to note that reactions are continually reacting, so if something is changed, it will want to go back to its original equilibrium state.

Rita Chen 1B

Wait how do you know whether a coordination compound is a chelate? For example, how do you know that [Ni(NH3)2O2]Br2 is not a chelate?

Rita Chen 1B

How would ew determine that HN(CH2Ch2NH2)2 is polydentate? Do we need to draw it out? If so, how do you know how ot draw it?

Rita Chen 1B

Will we be given the ligand names in coordination compounds sheet that was sent out?

Rita Chen 1B

Do free radicals count as electron density?

Rita Chen 1B

I think this is because as you go down a group for binary acids, you are looking at the strength and length of the HA bond, not the polarity, so the weaker the HA bond, the stronger the acid.

Rita Chen 1B

I feel like we wouldn’t need to know that since its pretty complicated (ish)

Rita Chen 1B

Could someone explain conjugation in general and when we need it?

Rita Chen 1B

Which latin names do we need to know? for example, will we be given that Copper would be cuprate?

Rita Chen 1B

I would think that you would just need to know what counts, so like knowing that bidentate would be chelating, or when it counts as chelating (2 or more bonds to a metal ion)

Rita Chen 1B

I think this refers to how many bonds the ligands can make to an ion. So like for example, if you had C2H4, it would be bidentate, because it could bind to something like Zn2+.

Rita Chen 1B

Identify the salt that is produced from the acid-base neutralization reaction between potassium hydroxide and acetic acid.

How would I do this? I know it is supposed to produce water but the salt doesn't look quite right if I have more than 1 carbon

Rita Chen 1B

How do I know how to write these hybridization? How does it relate to shape?

Rita Chen 1B

Would it be okay to say that even though it is an intermolecular force, the stronger, the harder the bonds are to break?

Rita Chen 1B

Will pi bonds be stronger than sigma bonds? Or is there a way to tell whether there is a strength difference?

Rita Chen 1B

So does promotion just refer to having an electron be at a higher electron state/bringing it to a higher orbital?

Rita Chen 1B

I think you write OH2 to emphasize that it is not bound to the hydrogen, but to the metal of the ligand. I think either is fine, but if you wanted to emphasize the coordination compound it would be OH2.

Rita Chen 1B

Is CS2 non-polar because of symmetry?

Rita Chen 1B

How do I know which one is the central atom? If Be was the central atom, it would be linear right? But the solutions said tetrahedral about the carbon atom so I’m not sure which one I would put.

Rita Chen 1B

Why do lone pairs take up more space?

Rita Chen 1B

Do we need to know all the shapes or just the ones that he went over in class? I am looking at some of them and we haven't really discussed some of these before. Is it just his lectures, lectures + book, or lectures + book + everything else?

Rita Chen 1B

I think that you place it where it will have the largest distance so that it will stabilize the structure. Not sure if that is completely correct, I am confused a little too.

Rita Chen 1B

Why is CH2Cl2 going to have dipole-dipole interactions? Does the symmetry not matter?

Rita Chen 1B

Where is the dipole-dipole interaction in this? Is it with the O-H? Can someone explain to me what the dipole-dipole interaction really is because I only really know of the interaction between water molecules as being dipole-dipole, so how can one molecule have dipole-dipole interactions?

Rita Chen 1B

Where is the dipole-dipole interaction in this?

Rita Chen 1B

What happens to the antioxidants afterward?

Rita Chen 1B

Do you guys think if I wrote it in the wrong order, it would be ok? Or would it be partial credit.

Rita Chen 1B

I was wondering whether this goes for the ones below as well. I was a little confused whether these exceptions are for all of the ones that follow the same atom trend.

Rita Chen 1B

Does anyone know what Test 2 will be on? Will it be a cumulative kind of test, or just on the new sections?

Rita Chen 1B

I think that week 7 homework is on anything that we learned during discussion or if there is a test, whatever it is like a test. But honestly, I think that if you do the questions for the material covered in that week, it would be okay.

Rita Chen 1B

When do we need to use brackets? And also for ionic compounds, will we always write them separately with brackets, adding the electron on the anion?

Rita Chen 1B

If it is asking about the threshold, it is usually the total kinetic energy of the incoming light minus the energy of the electron emitted, while kinetic energy it could be talking about the kinetic energy of the electron emitted, or the photon itself. If it is talking about the source, usually it w...

Rita Chen 1B

For the midterm, do you know what will be provided in terms of sheets? Like will we be given electronegativity values? Or bond lengths?

Rita Chen 1B

Can someone please explain the two classes for chem 14B and chem 14BL? When should we be taking it? I heard that you can take it at the same time. but do most people take it at the same time?

Rita Chen 1B

Which polyatomic ions will we need to know? And do we need to know naming and to what extent?

Rita Chen 1B

Can someone please explain to me what it means by ground-state? What is the difference between ground state and excited state?

Rita Chen 1B

I think Ga would likely be 3+ because it has 3 valence electrons.

Rita Chen 1B

Can someone please explain to me how to do part B of 2A.5? I don’t get how to incorporate the F-block.

The question is Give the ground-state electron configuration expected for Bi3+.

Rita Chen 1B

I was wondering if someone could explain to me more about the electron-electron repulsion that makes the atomic radii bigger (I think). Does it matter that much and which one has a bigger impact, the pull from the protons or that repulsion?

Rita Chen 1B

Because class was cancelled, and there was materiel that we were supposed to go through today, does that mean there will be less material on the midterm or will he just speed up the class time learning?

Rita Chen 1B

Does anyone know when we need to use noble gas configuration (simplified) rather than the traditional long electron configuration?

Rita Chen 1B

You can think of it like you are making an atom that is already more positive than it should be, even more positive. It will be harder because the atom wants to keep that electron and you are taking it away from its stable form and the form in which it has no net positive or negative charge.

Rita Chen 1B

Knowing the ionization energy and electron affinity (electronegativity) is probably the most important. It may also help to know the trends in the size of these atoms because it can really help you determine the other two. The other two are important because they can help you determine what will be ...

Rita Chen 1B

The strength of a bond is affected by the charge and distance for ionic bonds. The strength of a bond is affected by the electronegativity differences and the bond length. Generally, double bonds are stronger than single bonds and triple bonds are stronger than double bonds. We will probably need to...

Rita Chen 1B

Test 2 will be during your discussion session from week 8 starting from November 19th!

Rita Chen 1B

I think if there is one they don’t expect you to know, they will put it on the sheet. The ones you should know are the ones we went over in class though. Any other conversions that are semi-difficult should be put on the sheet.

Rita Chen 1B

Can someone please clarify what Dr. Lavelle said about putting 3d in front of 4s? Thank you!

Rita Chen 1B

The letters themselves represent a word. S represents sharp, p represents principal, f represents fundamental and d represents diffuse.Thi sis from the spectra of the alkali metals.

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