CHEMISTRY COMMUNITY

Parsia Vazirnia 2L

Under what conditions will reactions likely occur at room temperature? When the gibbs free energy is smaller? Why?

Parsia Vazirnia 2L

Does anyone have an organic chem kit I can borrow to help study? Really need more help visualizing the molecules. I am having trouble identifying between trans and cis cyclohexanes.

Parsia Vazirnia 2L

Hydroxy is used when there are two or more functional groups in the molecule. When there is an alcohol plus another functional group, instead of the ending being -ol, we note the presence of an alcohol by using hydroxy-. When the alcohol is the only functional group in the molecule, we denote it wi...

Parsia Vazirnia 2L

Is cyclohexene really benzene?

Parsia Vazirnia 2L

then they could potentiall be both?

Parsia Vazirnia 2L

Are halogens considered nucleophiles or electrophiles? They would want to complete their octet of electrons so they would be electrophiles correct?

Parsia Vazirnia 2L

On the bottom of page 85 of the course reader, how do you know that Step 1 is slower and has a higher activation energy than step two? Can someone apply this to 4.29 in the green book? Will the reaction profile always look like this?

Parsia Vazirnia 2L

Pratyush Kandimalla 2O wrote:Please find attached the recording of winter 2017 post midterm review

I love you pratyush <3

Parsia Vazirnia 2L

Could someone please explain to me part C of number 65 on chapter 15 homework? Why would increasing the temperature increase the rate constant of the reaction with the higher activation barrier more than it will the rate constant of the reaction with the lower energy barrier?

Parsia Vazirnia 2L

What in tarnation!

Parsia Vazirnia 2L

Hi in the quiz we had a question that stated "which molecule, when a single crystal, would you predict to have a larger molar entropy T=0K". Two crystals were then given with the same geometry. I know that you had to take the r the positional/residual entropy and degeneracy into account. W...

Parsia Vazirnia 2L

Hi, Im a bit confused because the values given in question 55 and what is given in the solution manual are not consistent. In the book, it is given that the standard potential is -0.42 volts for water but in the solutions manual it is written that the standard potential is -0.83V. Which value did yo...

Parsia Vazirnia 2L

Hi,
I'm solving for number 47 and I get that lnQ=15, which is the same answer in the solutions manual. Now solving for Q I get e^15. I do not understand how the solutions manual got Q=10^6 as an answer? Even if you write lnQ as Log(base10)Q, you would get that q=10^15 not 6. Can anyone explain please?

Parsia Vazirnia 2L

Can someone explain number 43 in the homework? I do not understand the explanation given in the beginning of the problem in the solutions manual

Parsia Vazirnia 2L

For the equation of H2S (aq) + Cl2 (g) ===> S (s) +Cl- (aq), why is H2S being oxidized? I am trying to write the two balanced half reactions. I know that CL2 is being reduced because it gains a - charge and therefore gains electrons. I am having trouble figuring out the charges on H2S and S because ...

Parsia Vazirnia 2L

will the upcoming midterm cover chemical kinetics?

Parsia Vazirnia 2L

I second this. I need help on this problem as well.

Parsia Vazirnia 2L

Can someone further explain the diagram on page 30 of the course reader in which the mass is decreasing slowly? I was having a hard time understanding this during lecture.

Thanks

Parsia Vazirnia 2L

For part a, of question 75:

N[2] + 3F[2]=>2NF[3]

Why are we forming 6 mols of N-F bonds? Why not 2 mols? For example 2(-270 KJ/mol) instead of 6(-270 kj/mol)?

Parsia Vazirnia 2L

If we have say for example -300 J of work done but also have another value of -200J of work done. Why is -300J more work done? Why is the sign convention irrelevant?

Parsia Vazirnia 2L

When can I just use the initial moles when using an icebox table instead of the initial concentration?

Parsia Vazirnia 2L

It would be very helpful to me and other students if you could copy the question in your post. Unfortunately I don't have my book with me and don't know what question you are referring to. I'm not sure what the answer to part D is, but if it is close to 7, I believe that it could still be considere...

Parsia Vazirnia 2L

Why is the answer to part D of 12.65 neutral and not basic with a ph>7?

Parsia Vazirnia 2L

the H3- is electron-donating relative to hydrogen and it donates electrons to the carboxyl group which makes it more negative. This causes the acid to be weaker, because the proton now has to be separated from a more negative conjugate base. likewise, CH3CH2- is more electron-donating than CH3-, an...

Parsia Vazirnia 2L

When trying to find the concentration and you have a -x in your K expression, when can you drop the -x in your calculations? for example lets say you are given the value of Ka and it is 3 X 10^-6 and you set it equal to the expression which is X^2/0.20-X. Under what conditions can you ignore the -X ...

Parsia Vazirnia 2L

Why is formic acid more acidic (HCOOH) than acetic acid (CH3COOH)?

Parsia Vazirnia 2L

Hi for problem number 39 on chapter 12, why are we subtracting 14 from the pkA value? why is (Ch3)2NH2+ and +NH3OH bases? They have protons to donate

Same goes for problem number 41 except vice versa the question involves pKb

Parsia Vazirnia 2L

Is Bi2O3 amphoteric because it is next to the diagnol on the periodic table of elements or basic because as you go down the periodic table of elements a compound becomes more basic.

Parsia Vazirnia 2L

Q: What do you call an acid with an attitude?
A: A. A-mean-oh-acid.

Parsia Vazirnia 2L

Why is the coordination number for (en) equal to 6?

Parsia Vazirnia 2L

In lecture it was mentioned that we use the reaction quotient Q at any time whenever the reaction has not reached equilibrium, and we use the K constant for whenever it is in equilibrium. My question is how are we supposed to know if a reaction is in equilibrium or not? When do I know to plug into t...

Parsia Vazirnia 2L

So If a complex has a net negative charge, you would add ate at the end of the metal name. Can someone explain why for K3[CoF6] becomes potassium-hexa-flouro-cobaltate (III).Why are we adding "ate" to cobalt. Where does the negative charge come from?

Parsia Vazirnia 2L

Hello,

Can someone summarize adding vectors and vector addition for dipoles and figuring out the net dipole.

Parsia Vazirnia 2L

All material covered in Fundamentals and Chapters 1-4 up to the end of hybridization. Course Reader: All material up to page 105. Past Midterms in Course Reader: Pages 179-217 For more info go to this link: https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=157&t=16342 Will it cover material t...

Parsia Vazirnia 2L

I noticed that in the course reader the definition for Formal charge is that it "indicates gain or loss of electrons while forming covalent bond". So can you find the formal charge for an ionic bond?

Parsia Vazirnia 2L

(Cations) Group 1 elements will have a +1, group 2 elements will have +2, and group 3 as +3, group 4 as +4 because they are losing an electron. (Anions) Group 15 as -3, group 16 as -2 and group 17 as -1 because they are gaining 1 electron. Group 18, the noble gases are stable so they do not have a ...

Parsia Vazirnia 2L

yes I understand that but like how would you know that Fe has a +2 charge and same goes with Ca2+, Cl-

Parsia Vazirnia 2L

How do you know if an element is a cation or an anion?

Parsia Vazirnia 2L

Hello, I am looking at an example on page 48 that says that lead has the same number of valence electrons as carbon. The electron configuration for lead is [Xe]4f^14,5d^10,6s^2,6p^2. I understand that the f,d, and s orbitals have their orbital filled so you would just re write lead as [Hg]6p^2. Why ...

Parsia Vazirnia 2L

Hello, So now that we talked about excited electrons in hydrogen atoms, what would happen if a multi-electron atom is excited? Would the electron configuration just be higher than what is predicted or what we would expect by the building up principle? In the book it says that electron configuration ...

Parsia Vazirnia 2L

Hi, Where does the Na(N03) come from in the products side of the equation? The question only mentions that it produces a precipitate of light blue copper(II) hydroxide.I know there must be a sodium in products side because we have one in the reactants, but how do you know its Na(N03) because it is n...

Parsia Vazirnia 2L

So what you are saying in the second part of your answer is that deltaE becomes negative and you set that equal to the Rydberg formula which would be negative and the two negatives on both sides would become positive (mathematically dividing both sides by -1)?

Parsia Vazirnia 2L

Hi, For question 57 on the homework, involving lines in the Balmer series, it says in the solutions manual that "n[1]=2 so the fifth line in the spectrum should be n[2]=7. Then you plug into the Rydberg equation and find the fifth wavelength of the fifth line. What I dont understand is why you ...

Parsia Vazirnia 2L

Can someone explain the concept behind the 1:1:1 of 1 photon 1 atom and 1 electron for the photoelectric effect and the formula I(intensity) proportional to the number of photons?

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