CHEMISTRY COMMUNITY

BeylemZ-1B

what section of chapter 7 is this from, so i can reference my work

BeylemZ-1B

in the homework there were some reactions (7A and 7B) that were larger than second order. We don't need to know much about these (like how to graph them), right?

BeylemZ-1B

in the homework there were some reactions (7A and 7B) that were larger than second order. We don't need to know much about these (like how to graph them), right?

BeylemZ-1B

Hi, I attached some helpful information that I wrote regarding pseudo ordered reactions. Essentially, pseudo ordered reactions are used when you have more than one reactant and one (or two) of the reactants is in excess. Because they are in excess, we can assume their rates are essentially constant...

BeylemZ-1B

I would say so for the most part. The hardest part is discerning whether it is a first, second, or zeroth order reaction. Don't count on just knowing the basic equations for the final though, I would make sure you are well versed in the reaction graphs (section 7B) and how to analyze them.

BeylemZ-1B

to ease some stress before the final, know that we will most likely not be asked to graph these ourselves by hand, but maybe only asked to interpret graphs. KEY IS TO REMEMBER:
zeroth: [A]t vs t (-k)
first order: ln[A]t vs t (-k)
second order: 1/[A]t vs t (k)

BeylemZ-1B

Basically, if there is a reaction that appears to be 2nd order, we can assume that there is excess reactant in a pseudo first order. The concentration of excess reactant is treated as constant since the change in the amount of excess reactant is negligible as the reaction proceeds. So now we treat t...

BeylemZ-1B

i found this video really helpful since the textbook barely explained this concept.
https://youtu.be/0BTyxuVRLf8

BeylemZ-1B

Definitely Enjoyed Kinetics from 14B the most, and I especially loves molecular shape and structure from 14A. I am a visual learner

BeylemZ-1B

so if both are first order independently, does this make the reaction an overall 2nd order reaction?

BeylemZ-1B

Will the instantaneous rate always decrease as the reaction proceeds? is there ever a chance we will see a reaction where the rate of reaction increases as time increases?

BeylemZ-1B

You can also think of this graphically. I doubt we will ever be asked to do this by hand on a test, but if you graph the concentration [A]t vs time and you get a straight line, it is zeroth order. If you graph the natural log of the [A]t vs time and get a linear graph, it is first order. if you grap...

BeylemZ-1B

Since .034M of product B was created, than (according to the stoichiometric coefficients) we can assume that 2(.034M) of reactant A was consumed.
We then subtract .153(initial concentration of A) - 2(.034M) = .085M
.085M = [A]t

BeylemZ-1B

Melissa Villanueva1K wrote:Is there a possibility that there will be graphs given or we will have to draw graphs in accordance to the order of the reaction? Thanks!

since none of the assigned homework problems had us drawing graphs ourselves and finding slopes, I doubt we will be expected to on a test.

BeylemZ-1B

If you look at how half life is derived from the original 1st order reaction equation the initial concentration is canceled out when deriving the half life, which is why it doesn't matter. let's work this out: we know ln([A]t/[A]0) = -kt if we divide both sides by (-k), we get: t = (1/k)*ln([A]0/[A...

BeylemZ-1B

Now that we have [A]0, we can plug it into out first order reaction equaition

[A]t = [A]0*e^-kt
[A]t = [.00004148]e^-(2.8E-3min-)(90min)

[A]t = .0000322M

now you convert this back to grams...
.000032mol/L * 2500L * (135g/mol) = 10.8grams

BeylemZ-1B

so we know k=2.8E-3 min-1 1.5 hours=90 minutes let's convert 14.0 grams to moles 14.0 g / (135g/mol) = .1037 mol, then divide by total liters to get an initial molarity of .000041481.... seeing that your final molarity is so high, I would go back and check this first step with your work too see wher...

BeylemZ-1B

after you get the new concentration [A]t = 0.085, you can set up the equation to solve for the rate constant:

ln[0.085] = -k*(115 seconds) + ln[.153]

so I got k=5.1E-3, but what would the units be and how do I differentiate the units on k for first and second order reactions?

BeylemZ-1B

what’s the difference between the integrated rate laws vs the general rate law? think of driving in a car (this is example used in textbook). general rate law is like saying you took an hour trip, and ended up driving 30 miles. your average (general) speed for the entire hour time period is 30 mph....

BeylemZ-1B

How are you supposed to know something is Zeroth order? is there a specific rule to know that it is zeroth order?

BeylemZ-1B

think of this being like an ICE chart (except we aren't really talking about equilibrium, just a helpful model to figure out proportions): A B C I: .015M 0M ... C: -.006M +.018M .... E: .009M Since we are only considering the rate in terms of the consumption of A, then we only need the final concent...

BeylemZ-1B

we know from the unique rate equations for a reaction:
aA + bB --> cC + dD

the rate = -(1/a)d[A]/dt, -(1/b)d[B]/dt, (1/c)d[C]/dt, (1/d)d[D]/dt.
The stoichiometric coeff goes on denominator of the rate of production or consumption. I think this should help you.

BeylemZ-1B

can someone help explain the stopped flow technique to measuring the rate of a really quick reaction? After reading about it in the textbook and looking at the diagram I still don't understand.

BeylemZ-1B

WRITE balanced half reactions for the redox reaction of an acidified solution of potassium permanganate and iron(II) chloride.

Step by step help on this one please. How do I express an acidified half reaction?

BeylemZ-1B

Write half reactions and devise a galvanic cell to study each of the following reactions: (C) Cd + Ni(OH)3 —> Cd(OH)2 + 2Ni(OH)2 I don’t understand how in the answers for the homework, the half reaction for cathode looks like : Ni(OH)3 + e- —> Ni(OH)2 + OH- and then the cell diagram for the right si...

BeylemZ-1B

I’m also very confused because in the textbook answers, it says the anode reaction would be Ag + Br- —> AgBr + e- and the cathode rxn would be Ag+ + e- —> Ag. How are we supposed to infer this from just being given the reaction
AgBr <—> Ag+ + Br-

BeylemZ-1B

I’m also very confused because in the textbook answers, it says the anode reaction would be Ag + Br- —> AgBr + e- and the cathode rxn would be Ag+ + e- —> Ag. How are we supposed to infer this from just being given the reaction
AgBr <—> Ag+ + Br-

BeylemZ-1B

Oxidation occurs in the anode and Reduction occurs in the cathode. In this problem, Au is both the oxidizing and reducing agent. Au+ is being oxidized when it goes to Au3+ since it goes from having an oxidation state of +1 to +3. It is being reduced when Au+ goes to Au(s) since it goes from having ...

BeylemZ-1B

“Write the half rxns, the balanced rxn, and the cell diagram for each of the following skeletal equations...
...(d) Au+ —> Au + Au3+

Can someone explain to me how to write the haLf reactions for this ?

BeylemZ-1B

d) P4 (s) ---> H2PO2(^-1) (aq) + PH3 (aq)

I know how to balance the reduction reaction, but can someone explain how to balance the oxidation reaction ?

BeylemZ-1B

I had the same question. but I guess if it's a typo then it makes sense. If there were to be Cl2 on both sides of the equation would it be solvable? if it had Cl2 on both sides, they would cancel i believe and it wouldn't be solvable. You have to take into account the typo as mentioned above: "...

BeylemZ-1B

I am confused on 6K.1 part a. I thought from previous high school chemistry that the species being reduced or oxidized had to be metal (like Fe or Cu) and that is what is typically seen in all the examples from class. I can easily see that Cr is being reduced, but what is being oxidized because I do...

BeylemZ-1B

It is mostly used to balance redox reactions that happen in aqueous solutions of H2O. This is because in these aqueous solutions, water can dissociate into H+(meaning there will be acidic conditions) or water can dissociate into OH- ions (meaning there will be basic conditions). With this added fact...

BeylemZ-1B

Why do electrons have to cancel when you balance the half reactions ? (why would the electrons released by oxidation have to be the same as the number used in reduction??)

All i know is that it has to happen, but i don't quite understand why.

BeylemZ-1B

it is actually not only dependent on proton transfer! i believe you are thinking of bronsted-lowry acid and base reaction from 14A. ReDox rxns depend on the transferring of charges based on electron gains and losses. LEO says GER! Lose Electrons: Oxidation Gain Electrons: Reduction (fun acronym to r...

BeylemZ-1B

When writing the half-reactions for redox equations, we get something along the lines of ...
AG+ + e- ---> AG(s) (reduction, gaining electron).
Can the single electron actually exist as an electron in space?
I didn't think it could, so if not, why do we write it this way?

BeylemZ-1B

On part C of this problem, why would the change in internal energy of the system be different then how much work is done in the compression? w= -Pex(deltaV) where Pex= constant external pressure delta V= Vfinal-Vinitial ( the expansion/compressiom of the system) when deltaV is positive , the intern...

BeylemZ-1B

On part C of this problem, why would the change in internal energy of the system be different then how much work is done in the compression?

BeylemZ-1B

After you calculate the dimension change of the pump, you multiply by the external pressure, which is given as 2 atm. Remember to convert this to pascals, whether that is before or after the calculation. This should give you an answer of 28.

BeylemZ-1B

If you look at the graph provided in the question, you will be able to determine the amount of A consumed and the amount of B and C formed in reaction in establishing equilibrium. If you set up an ICE table and plug in the initial and equilibrium partial pressure values, you can determine the chang...

BeylemZ-1B

Shannon Asay 1C wrote:It would increase the formation of X because the reaction is endothermic and an increase in the temperature would increase the k value. This means an increase in the number of products.

How would you know it’s endothermic? Is it because breaking a halogen apart requires heat?

BeylemZ-1B

has anyone done the peer learning worksheets? are the problems beginner level to provide guidance or a great tool to use when studying for the tests? I just took the test today and I think the peer learning worksheets are really great for nailing the fundamentals metals and if you have the time you...

BeylemZ-1B

So In 5J.11 b, the equation is X2->2X, where x is a halogen. In this equation, it is essentially breaking a bond, which means it requires energy and is endothermic. In an endothermic reaction, when you raise the temperature, the value of k increases. If k increases, that means the equilibria is fav...

BeylemZ-1B

Amanda Lin 2I wrote:Endothermic reactions favor the formation of products.

I think this is too general of a statement. Endothermic reactions favor the products when the reaction is heated.

BeylemZ-1B

I see now that there are two moles on the right side of the equation and 2 moles (one mole of H2 and one mole of D2), which means there is no overall change with volume change

BeylemZ-1B

For problem 35 at the end of chapter 5, how do you know the balance to Quetion between the reactant A and the two products B and C?

BeylemZ-1B

On problem number 33 at the end of chapter 5, why would increasing the temperature increase the formation of X? I thought there would be no change.

BeylemZ-1B

Definitely DEFINITELY master the ice tables. I think it’s a good idea to go back over homework problems with either a really small K or a really large K when you can use the method of estimating.

BeylemZ-1B

Why would 5J.11 part b favor the products? I thought there would be no change when heating.

BeylemZ-1B

Can someone explain to me why the answer to 5J#5 part D is No Change? I thought it would be the reactant favored.

BeylemZ-1B

What i remember from high school chemistry is a rule about "-ate" and "-ite" if the anion in the acid ends in "-ate," the new name of the acid is now "-ic" if the anion in the acid ends in "-ite," the new name of the acid is now "-ous" for ...

BeylemZ-1B

I understand the rule that any acid with a carboxyl group is considered a weak acid. Why?

For example:
CH3COOH is a weak acid.

BeylemZ-1B

would a really weak base be close to 7? or as far away from 7 as possible?

for example:
would a pH of 8 be more or less basic than a pH of 12?

BeylemZ-1B

Might also be important to know that carbonic acid is formed by the reaction of water and CO 2 , which happen to be the products of cellular respiration. this refers to acid rain. also remember that CO2 is a product of A LOT of other biological and inorganic processes, like decomposition and pollut...

BeylemZ-1B

Yes! this is very true and can be seen through hydrochloric acid (HCl).
HCl(aq) is a very strong acid. The conjugate base of HCl is Cl-(aq), which is also a very weak base.

BeylemZ-1B

The roman numeral indicates the positive charge of the transition metal cation. This notation is often used since transition metals can take on multiple oxidation states. For example, to distinguish Fe 2+ and Fe 3+ you would write Iron (II) or Iron (III). If we have the coordination compound [Co (N...

BeylemZ-1B

If i were given a random acidic compound, how would i go about determining if it is strong or weak?

BeylemZ-1B

can someone explain the difference between clean coal and dirty coal? I remember it being explained in the lecture in terms of Carbon of Sulfur dominant, but I don't remember which was clean and which was dirty.

BeylemZ-1B

can someone help me with finding the oxidation numbers it is asking for in homework question 9C.5?

BeylemZ-1B

I'm not sure why Bi would be since it is not in the band of the Amphoteric elements discussed in lecture...
...Be, Al, Ga, Sn, Sb, Pb are the elements that i was able to record in lecture, and i have the same question about Bi.

BeylemZ-1B

What are the VSEPR formulas (e.g. AX2E) for the two different types of molecules that are T-Shaped?

BeylemZ-1B

The question is: Draw the Lewis structure and predict whether each of the following molecules is polar or nonpolar. The molecule I am confused about is CH2Cl2 because I put the two hydrogens on opposite sides of the carbon atom and the two chlorines on the other two sides on the carbon, which cance...

BeylemZ-1B

to add to the person above, the highly polarizable atom is typically a very large anion. when polarizability is high, typically it means the anion is extremely large, with electrons distant to the nucleus. When you mix a very large anion with a very small highly charged cation, you get strong forces...

BeylemZ-1B

to add on, typically, the larger the molecule, the larger the polarizability. this is because the electrons are farther away from the nucleus and the valence electrons are more shielded from the pulling power of the nucleus.

BeylemZ-1B

Typically, you look at the molecule as a whole when describing pi and sigma bonds. So every resonance structure would have the same number of sigma and pi bonds. But as the response above has stated, I would just draw in the specific pi and sigma bonds for each resonance structure if a test or homew...

BeylemZ-1B

Rita Chen 1C wrote:What happens to the antioxidants afterward?

Afterwards, the antioxidants are simply excreted from the body! typically in the form of urination

BeylemZ-1B

Also keep in mind that bond length has an inversely proportional relationship with bond strength.

As bond length increases, bond strength decreases. (vice versa)

BeylemZ-1B

So revisiting the original question, does one play a more significant role than the other (size or charge?). If so, why?

BeylemZ-1B

can someone explain why the size of the cation plays a role in how polarizing it can be?

BeylemZ-1B

First, I just set up the molecule as described in the problem. From there, I added all of the 22 other electrons onto the atoms to give them octets. At first I gave Cl 6 free electrons, Oxygen 4, Nitrogen 0 and each of the oxygens 6. However, with this setup, nitrogen didn't have an octet. So, I mo...

BeylemZ-1B

If your lewis structure is correct, there will be a double bond between Xe and O, single bonds between each F and the Xe, and a lone pair on the central atom, Xe. Now you take the equation for formal charge = V - (L + 1/2*B) Since Xe is in the very last group it has a value of V = 8. There are 2 lon...

BeylemZ-1B

are we supposed to know this already??? This type of bonding was just touched on in lecture recently, so its ok if youre not extremely familiar with it. These four types of interactions are all pretty much the same if I am not mistaken: 1. dispersion = 2. induced dipole - induced dipole = 3. London...

BeylemZ-1B

Can someone explain how the anions distortion somehow makes the ionic bond now have covalent characteristics?

BeylemZ-1B

Can someone describe the trends in the periodic table referring to Electron Affinity? I understand that it is the energy released when an electron is added, but i do not quite understand how i would be able to qualitatively decide which elements have a higher E(ea) value.

BeylemZ-1B

What is the difference between 1st ionization energy and second ionization energy? As discussed in a previous lecture, removing a second electron always requires more energy than removing the first electron. looking at this example of Copper: Cu(g) --> Cu+(g) and e-(g) with a first ionization energ...

BeylemZ-1B

What is the significance of the direction in which an electron spins? the directions an electron spins is merely for the purpose of qualitatively analyzing. the "spin up" and "spin down" don't literally mean the electrons are spinning in a clockwise or counterclockwise direction...

BeylemZ-1B

in lecture, lavelle really only said we needed to be familiar with s, p, and d blocks when writing electron configurations . but in homework problem 1D.21 part C, the answer was in terms of the f orbital. do we still only need to know the s, p, and d blocks, or should i familiarize myself with "...

BeylemZ-1B

in lecture, lavelle really only said we needed to be familiar with s, p, and d blocks when writing electron configurations . but in homework problem 1D.21 part C, the answer was in terms of the f orbital. do we still only need to know the s, p, and d blocks, or should i familiarize myself with "...

BeylemZ-1B

Can someone explain to me why the quantum numbers for 1E.9 part B are not possible? I understand part A and C, but something about B is really throwing me off.
Thanks so much!

BeylemZ-1B

nicknavejas1B wrote:I heard Professor Lavelle mention that we wont need to prepared to be tested on this concept, can anyone confirm?

it will not be tested, but i read over it in the textbook because i feel the information provided was interesting, yet very confusing.

BeylemZ-1B

Rithana Srikanth 3L wrote:I think you would have to draw the Lewis structure to figure it out.

do we need to know how to draw lewis structures for our test over the quantum world?
I would need to brush up on that (even though it is literally so simple haha)

BeylemZ-1B

You always remove electrons from the highest energy orbital As an example, you would remove electrons from 4p before you would pull from 4s.

BeylemZ-1B

I'm really stressed out right now. The textbook is a lot of information with lots of formulas to know. Any advice for understanding the material better & to help me feel more prepared & confident? if you are referring to the section in the textbook 1D that has the chart of all the formulas,...

BeylemZ-1B

Does anyone know if Dr. Lavelle will be uploading any further modules on the rest of the Quantum Unit? I find them extremely helpful and would love to have more.

BeylemZ-1B

McKenna_4A wrote:When Dr. Lavelle states that light can be at "higher intensity," what does this mean with respect to wave properties?

Intensity can be found mathematically too! Intensity = (Amplitude)^2 if i am not mistaken.

BeylemZ-1B

On tests (for Dr.Lavelle and I am sure all other professors) you are given both a formula chart AND periodic table to assist you.

BeylemZ-1B

Yes! definitely would need to change from km*g to m*kg!! thanks to metric conversions the dimensional analysis is quite straightforward.

BeylemZ-1B

When trying to find the velocity of an object, how do you know whether to use the equation v=c/(wavelength) or v=h/(mass x wavelength)? the "v" is not in reference to velocity as it would be in Physics. the "v" is the frequency of the light!! definitely a distinction that needs ...

BeylemZ-1B

i think WHAT happens was explained, but i am still not understanding exactly WHY the temperature is seen to increase. Can anyone explain to me in a different light what is going on here?

BeylemZ-1B

The rydberg equation, if i am correct, is derived from Bohr's equation. Dr. Lavelle prefers to use Bohr's over the Rydberg equation though.

BeylemZ-1B

Can someone explain to me in more detail what amplitude is? I was not quite sure when it was explained in class.

BeylemZ-1B

You only have to imagine there is 100 grams when %composistion is given but not the mass. (the number of grams you used is not fixed, you can use whatever you want as long as you keep the calculation simple and clear, but usually, 100 grams is the most straightforward and simple) I definitely agree...

BeylemZ-1B

I believe that is would be helpful to know the two opposing ends of the spectrum, with red and blue light, and where they fall into the entire Electromagnetic spectrum.

BeylemZ-1B

If i am not mistaken, the electric field no and magnetic field are perpendicular in a 3 dimensional space.

BeylemZ-1B

Does that mean 114.0 would be 4 sig figs?

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