CHEMISTRY COMMUNITY

Lilly Catarozoli 1B

As others said, it is possible but not very likely!

Lilly Catarozoli 1B

You can sum up the exponents from the rate law or look at the graphs!

Lilly Catarozoli 1B

I think it was in Wednesday's lecture!

Lilly Catarozoli 1B

I was confused too, so thank you!!

Lilly Catarozoli 1B

Gibbs free energy tells us if the reaction is spontaneous or not.

Lilly Catarozoli 1B

The pseudo rate law assumes that the other reactants are in large excess and so you can measure the isolated reactant. It is like what Lavelle said about taking 3 dollars from someone who has one million dollars!

Lilly Catarozoli 1B

Determining K depends on the question. You can use the graphs or can calculate K based on what variables are given in the problem.

Lilly Catarozoli 1B

Hi! We covered multiple reactants in Friday's lecture (3/5).

Lilly Catarozoli 1B

I do not think there is. I think it is experimentally determined.

Lilly Catarozoli 1B

The units should work out when you do the equations. But generally, zero order is M/s, 1st order is 1/s and 2nd order is 1/M*s.

Lilly Catarozoli 1B

The log equation is only used when the reaction is at 25C or 298K. The ln equation is used any other time.

Lilly Catarozoli 1B

E naught is zero because the concentrations are equal in the cell.

Lilly Catarozoli 1B

Water is used if the oxygens are not balanced.

Lilly Catarozoli 1B

I like using OIL RIG but I think any acronym is helpful to remember it!

Lilly Catarozoli 1B

Hi! You shouldn't need knowledge from 14a (though we touched on it briefly) but just remember that strong oxidizing agents are easily reduced.

Lilly Catarozoli 1B

In aqueous solutions, you need a conductor so if no metal is listed you need to add P(t).

Lilly Catarozoli 1B

Yes the anode is on the left and the cathode is on the right.

Lilly Catarozoli 1B

Standard reduction potential is the power of gaining electrons/being reduced.

Lilly Catarozoli 1B

Hi! When we want to freeze liquid water at 0 degrees Celsius, we use deltaS = Hfusion/T. Why do we make Hfusion a negative value? It is listed as 6.01 KJ/mol, but in calculations, we make it negative (example question 4F.13). Why do we do this? Thanks!

Lilly Catarozoli 1B

Hello! The problem is, "Write a balanced chemical equation for the formation reaction of (a) NH 3 (g ) ; (b) H 2 O (g ) ; (c) CO (g); (d) NO 2 (g ) . For each reaction, determine Δ H °, Δ S °, and Δ G ° from data in Appendix 2A.
How would you approach this problem? I am pretty lost, thanks.

Lilly Catarozoli 1B

How do you know if a reaction or system is reversible or irreversible? Thanks!

Lilly Catarozoli 1B

Delta Ssurr is -delta H/ T and then Suniverse is the sum of the other two answers.

Lilly Catarozoli 1B

Everything is right except it is final - initial. Then your calculations should work!

Lilly Catarozoli 1B

Hello! Sometimes I have noticed we omit n in calculations for thermochemistry and sometimes we have to use PV=nRT to solve for n before doing further calculations (for example, #4 vs. #5 on sapling week 6 hw). When can we ignore n? Thanks!

Lilly Catarozoli 1B

Hi! The problem is: "Determine the reaction enthalpy for the hydrogenation of ethyne to ethane, C2H2+2H2---->C2H6 from the following data: Delta h sub c (C2H2,g)=-1300kJ.mol. Delta h sub c(C2H6,g)=-1560kJ.mol, and delta H sub c(H2,g)=-286 KJ.mol" I'm sorry but I do not even know where to b...

Lilly Catarozoli 1B

Sophia Wendin 3L wrote:I think the textbook answer of 90 x 10^2 is an error. The solution manual says the answer is 4.9 x 10^2 which is what I got when I solved for w = deltaU - q.

Thank you I was so confused!!

Lilly Catarozoli 1B

Thank you!

Lilly Catarozoli 1B

Hello! The problem is, "The internal energy of a system increased by 982 J when it was supplied with 492 J of energy as heat. (a) Was work done by or on the system? (b) How much work was done?"
I understand that work is done on the system, but how does work = 90 x 10^2 J? Thanks!

Lilly Catarozoli 1B

Hello! This problem states, "Air in a bicycle pump is compressed by pushing in the handle. The inner diameter of the pump is 3.0 cm and the pump is depressed 20. cm with a pressure of 2.00 atm. (a) How much work is done in the compression? (b) Is the work positive or negative with respect to th...

Lilly Catarozoli 1B

Textbook use J/gC, but I guess it could be Kelvin instead depending on what is given. I would just focus on making sure your units are all the same/cancel properly.

Lilly Catarozoli 1B

I think on a test Lavelle would give us the value. For homework, you can find accurate values in the appendix/back of book.

Lilly Catarozoli 1B

I think we just have to memorize a few of them (diatomic gases are in their most stable forms, solid carbon is in its most stable form, etc.) If it is outside of examples given in homework and class, I would expect Lavelle to clarify.

Lilly Catarozoli 1B

Bond enthalpies are the least accurate because they are averages. Standard enthalpies of formation are most accurate, then Hess's Law.

Lilly Catarozoli 1B

No! Lavelle basically never asks us to memorize constants. It will be given in the problem.

Lilly Catarozoli 1B

I think doing practice problems is the easiest way to learn. Basically, it is just flipping and multiplying the reactions to cancel out all reactants/products that you do not want. Just be sure to change the sign on delta H or multiply it! Whatever you do to the reaction, you have to do to delta H. ...

Lilly Catarozoli 1B

I can't find +NH3OH- or (CH3)2NH2+ on the table. Am I missing something or are we supposed to determine its strength without pKa?

Lilly Catarozoli 1B

For part b (using F2), I keep getting [F2]=2.38x10^-34 and [F]=0.0015. This does not match the solution manual. Does anyone else have this problem/know what I did wrong? Thanks!

Lilly Catarozoli 1B

This problem asks to calculate the pH, pOH, and percentage protonation of solute in each of the following aqueous solutions: a) 0.057M NH3 (aq). I am confused on how to solve this problem. The textbook gives me the and pKb, but how do I use these to get to pH? Thanks!

Lilly Catarozoli 1B

Thank you guys!

Lilly Catarozoli 1B

I was doing #25 from Problem 5I and when solving for x, neither one of the values was negative (one was 0.042 and the other was 0.019). How do you know which one to use if they are both positive? Thanks!
Also side note, for this problem I know you use 0.019 but I do not know why. Thanks!

Lilly Catarozoli 1B

The question is: "A reaction mixture is prepared by mixing 0.100 mol SO2, 0.200 mol NO2, 0.100 mol NO, and 0.150 mol SO3 in a 5.00-L reaction vessel. The reaction SO2(g) NO2(g) --> NO(g) SO3(g) is allowed to reach equilibrium at 460 C, when Kc 85.0. What is the equilibrium concentration of each...

Lilly Catarozoli 1B

In this problem, the initial concentrations are given for both of the reactants (SO2 and NO2) and one of the products (SO3 but NOT NO). How would you set up an ICE table for this reaction? For the reactants, would it still be -x, -x, and for the products +x, and +x? Or would this change because the ...

Lilly Catarozoli 1B

When solving for Q, if the concentrations are given in mmol/L, do you have to change them to mol/l? Thanks!

Lilly Catarozoli 1B

Total pressure is just the sum of all the partial pressures!

Lilly Catarozoli 1B

Use -log[H+] to get the pH and -log[OH-] for the pOH. You can also subtract from 14 to find one or the other!

Lilly Catarozoli 1B

You use -x when the reactants are turning into products and +x when the products are forming.

Lilly Catarozoli 1B

It could just be an algebra mistake. A lot of times it can be hard to type everything into the calculator correctly (I have made simple mistakes from this before!)

Lilly Catarozoli 1B

I think just how pressure, volume, temperature, and concentration changes the equilibrium of a reaction.

Lilly Catarozoli 1B

In this textbook problem, it says although (PO2)3/(PO3)2 is the same, (PO2)/(PO3) will be different. Why is this the case? I thought that they would both be the same. Thanks!

Lilly Catarozoli 1B

In textbook problem 5G-3, the H2O concentration is included in K. Is this because H2O is in its gas state? Thanks!

Lilly Catarozoli 1B

Lavelle seems to only use mol/L. I am not sure if other units are acceptable but in this class but it seems like we only need to know mol/L.

Lilly Catarozoli 1B

They are both constants. Ka is for acids and Kb is for bases.

Lilly Catarozoli 1B

How do we know when we can approximate x when using an ICE table? Thanks!

Lilly Catarozoli 1B

Is pKa just the log of Ka? Or are they related in a different way? Thanks!

Lilly Catarozoli 1B

When do we include water in K calculations? Lavelle said something about when it is not a solvent but I am still confused. Thanks!

Lilly Catarozoli 1B

This also confused me! I think it is just referring to K though.

Lilly Catarozoli 1B

I think the question would specify if it wanted a concentration (Kc) or partial pressure (Kp). If only gases are involved, I think it would most likely be Kp though. Hope this helps!

Lilly Catarozoli 1B

Liquids and solids are never included in K calculations because they don't have a concentration.

Lilly Catarozoli 1B

It depends on what the problem asks for! Use PV=nRT when you are converting from partial pressure to concentration or the opposite. For problems that ask for Kp, you'd plug in the pressure of each reactant/product instead of their concentrations. Hope this helped!

Lilly Catarozoli 1B

Qp and Qc are all Q just with different units (pressures vs. concentrations).

Lilly Catarozoli 1B

Hi! Just to clarify, Q and K are both the ratio of products over reactants, the only difference is that Q is used when the reaction is not at equilibrium? Thanks!

Lilly Catarozoli 1B

Higher Ka values indicate lower pKa values and lower Ka values indicate higher pKa values. They are inversely related.

Lilly Catarozoli 1B

As others said, if pH is less than pKa, then the environment is going to be more acidic. So, it is making an acidic environment more acidic.

Lilly Catarozoli 1B

Yes, I felt the same! I had no problems with time for the midterms but on this final, I was rushed.

Lilly Catarozoli 1B

Hi! The textbook asked for the hybridization of AsF3. I was confused why this would have hybridization since the electron configuration for As already has 3 empty spots for electrons ([Ar]3d10 4s2 4p3)? Can someone explain why this still uses hybridization? Thanks!

Lilly Catarozoli 1B

Hi! To determine bond angles, I use a VSPER Theory sheet that my TA gave us to study. But, in the textbook, I've noticed that sometimes the angle is different. An example is CH3-. I drew it and found that it was a trigonal pyramid and the formula was AX3E. So, the angle would be 109.5. But, the text...

Lilly Catarozoli 1B

Hi! The textbook question asked if SF4 was polar or nonpolar. I drew it and found that it was seesaw shape, so the dipoles do not cancel, so it is polar. But, the solutions manual says it is nonpolar. Am I missing something or is this a mistake?

Lilly Catarozoli 1B

The ligands are written in alphabetical order, but excluding the prefixes. Then, add the transition metal at the end. Hope this helps!

Lilly Catarozoli 1B

I believe Friday is a review session. Also, I believe in an email he said the final will focus on the material that we spent the most time on (quantum). Hope this helps!

Lilly Catarozoli 1B

A Lewis acid accepts electron pairs (ex. BF3) while a Bronsted acid donates a proton (ex. HCl). I think Lavelle said that Lewis definitions focus on the electrons while Bronsted definitions focus on the protons.

Lilly Catarozoli 1B

A Lewis acid accepts electron pairs (ex. BF3) while a Bronsted acid donates a proton (ex. HCl).

Lilly Catarozoli 1B

This question asked to draw the molecule and determine if it was polar or nonpolar. The molecule CCl4 was listed as polar, but I thought it would be nonpolar since the dipole moments cancelled out. What am I missing? Thanks!

Lilly Catarozoli 1B

Axial atoms form a 180-degree angle. They are vertical from each other (like above or below each other). Equatorial atoms are along the same equatorial plane. Dr. Lavelle went over some diagrams that helped me understand this!

Lilly Catarozoli 1B

Delocalized pi bonds correlate to the structure having resonance with double or triple bonds!

Lilly Catarozoli 1B

I think delocalized correlates to if the structure has resonance or not. If it has resonance, then the electrons would be delocalized because they don't have one singular place.

Lilly Catarozoli 1B

Bent and angular are the same thing!

Lilly Catarozoli 1B

I think just drawing them and seeing if the dipoles cancel out is the easiest!

Lilly Catarozoli 1B

P, S, and Cl, are elements that can have an expanded octet.

Lilly Catarozoli 1B

There is a crash course video that has good visuals and helped me understand. Hope this helps!

Lilly Catarozoli 1B

H bonding can only apply if there is a large difference in electronegativity, which is why it must be bonded to N O or F.

Lilly Catarozoli 1B

Everything has LDF regardless of the bond type!

Lilly Catarozoli 1B

Yes, because polarizability is the ability of the electrons to be distorted and electronegativity is about gaining and losing electrons!

Lilly Catarozoli 1B

For question 2B #23, the textbook answer says the structure to the right is the more likely. But, the structures on the right are the ones that have formal charges, while the structures on the left all have 0 formal charges. What am I missing? Thanks!

Lilly Catarozoli 1B

I think the textbook problems are the most helpful!

Lilly Catarozoli 1B

The way it fills matches up with the Aufbau diagram that I believe you are talking about, but when we write out electron configurations for this class, we would always go by increasing n levels. So, for example, even though 4s would fill before 3d, for a certain metal, lets say Ni, we would still w...

Lilly Catarozoli 1B

The most stable structure (the one with the least amount of formal charges) is the structure that contributes the most.

Lilly Catarozoli 1B

From what I understand, yes, London dispersion forces are always present regardless of bond type.

Lilly Catarozoli 1B

When I looked up the Aufbau Principle, it showed the diagram of the order that shells should be filled up (1s...5s, 4d). But, in the textbook answers, it lists 4d then 5s. What is the correct filling order for electron configurations? Thanks!

Lilly Catarozoli 1B

Thank you so much!!

Lilly Catarozoli 1B

The question in the textbook asks: How many orbitals can have the following quantum numbers in an atom: (a) n=2, l=1 b) n=4, l=2, ml=-2 c) n=2 d) n=3, l=2, ml=+1 For part a, I understand that the electron configuration would be 2p, so there are 3 orbitals. But for part b and part d, I don't understa...

Lilly Catarozoli 1B

Yes exactly! I like to draw diagrams, it helps me visualize where all the electrons are.

Lilly Catarozoli 1B

You can go to "Quick links" and then click "Your posts"

Lilly Catarozoli 1B

I thought the modules on his website were super helpful because there are concept questions too!

Lilly Catarozoli 1B

The expanded octect I think is more stable because atoms in those periods have d-orbitals which can have more electrons.

Lilly Catarozoli 1B

The d-orbitals have lower energy than the s and p orbitals!

Lilly Catarozoli 1B

I've heard it was the same!

Lilly Catarozoli 1B

I think they are double-checking the test so hopefully we get our scores back soon!

Lilly Catarozoli 1B

I dressed up as Rachel Green from Friends and painted pumpkins!

Lilly Catarozoli 1B

Maybe try rounding your answer differently?

Lilly Catarozoli 1B

You just need to divide the total energy by the work function from the step yu did before and then you should get the answer!

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