CHEMISTRY COMMUNITY

KBELTRAMI_1E

I can! Message me on GroupMe!!! Kallie Beltrami is my name to search

KBELTRAMI_1E

kendal mccarthy wrote:I am just going to put together a comprehensive study guide with a ton of example problems from outlines 1-6.

me too, probably with the equations and when they are useful, as well as side notes to remember when working through word problems

KBELTRAMI_1E

Parker Smith wrote:I'm having trouble understanding the half reactions of question 6.57. How do I derive the second half reaction from the first half reaction the problem gives?

Not sure, hoping to see the answer.

KBELTRAMI_1E

Because there hasn't been exhaustive coverage on thermo on any of the tests, I expect a decent amount of problems for that, as well as kinetics for sure, calorimetry and electrochemistry, and also equilibria. Maybe a thorough multi-part question on each.

KBELTRAMI_1E

yes most likely

KBELTRAMI_1E

Leonardo Le Merle 1D wrote:Could there ever be a reaction in which all reactants are zero order and thus the reaction itself is zeroth order? What would be an example of this?

quoting in case an example comes up

KBELTRAMI_1E

Unless you are given the precise change, you would just use x as an placeholder. For reactants, the change will be negative x, and for products the change will be positive x. Be sure to also account for the coefficients in the balanced chemical equation, if there is a coefficient of 2, then your ch...

KBELTRAMI_1E

Eva Zhao 4I wrote:In a closed system, energy can be exchanged with surroundings, unlike an isolated system in which nothing can be exchanged with the surroundings. The energy of a closed system can be changed by heating/cooling or compression/expansion (i.e. compressing a piston).

very helpful!

KBELTRAMI_1E

Standard free energy is measured in a lab under standard conditions (usually is denoted with a degree symbol). Delta G can be measured in a situation that isn't in standard conditions like in a biological system. So would we need to know anything more than just the sources of error/ comparison betw...

KBELTRAMI_1E

Like the diagram in class, you can tell that there is a phase change when the heat or enthalpy is increasing, but the temperature is not increasing, or delta T is zero. Can the enthalpy increase AND the temperature remains the same while there still not being a phase change? Like I'm imagining the ...

KBELTRAMI_1E

Brandi 2C wrote:I believe for "open book" it does entail classroom notes, office hour notes, discussion notes and packets, and everything in between.

What about -the internet-?

KBELTRAMI_1E

Michelle Song 1I wrote:Yes, it could happen if they all depend on the presence of a catalyst.

How so?

KBELTRAMI_1E

Like first vs second order? Negative as in less than a zero order? What would that be called and can you give an example if you found a problem with it?

KBELTRAMI_1E

Does anyone know how to scan from an at home wireless printer?

KBELTRAMI_1E

I'm not 100% sure but I've only seen products where the cathode is the product, but I think that's because its dependent on the direction the electrodes are flowing. If the charge is increasing then the product will be that of a greater charge, right? In most cases it is the cathode, as far as I know.

KBELTRAMI_1E

Without seeing your calculations, chances are one of two things happened. Either you did E anode- Ecathode which is backwards (should be Ecathode-Eanode) or you just made a minor calculation error with the double negative. Since the anode has a negative value AND is being subtracted, it will become ...

KBELTRAMI_1E

For the Nernst equation I've seen both ln and log used applied to Q and I'm confused as to which is correct or if they are used in different situations. Khan academy videos on Youtube seem to strictly use log but in lecture and discussion we've used ln.

KBELTRAMI_1E

Galvanic cells are also typically separated by a salt bridge whereas concentration cells are separated by a porous wall. In addition, the Ecell is typically lower voltage in concentration cell because the reaction is only driven by the difference in concentrations between the anode and cathode reac...

KBELTRAMI_1E

I believe that Lavelle mentioned that when it doesn't specifically state a temp, we typically assume its 25 degrees C which is 298K. However, I'm not sure if you need to know the temp for this problem.

KBELTRAMI_1E

do we need to know the standard formations for calculating delta H or will they be given to us if there is a question that requires them?

KBELTRAMI_1E

charleejohnson1L wrote:If we took that into consideration, we could never use measurements because they'd always be expanding or growing or something like that. Chem's a lot easier if you don't think super deep about it haha. :)

Thank you for responding!! This relieved a lot of my anxiety around the subject.

KBELTRAMI_1E

Standard free energy is measured in a lab under standard conditions (usually is denoted with a degree symbol). Delta G can be measured in a situation that isn't in standard conditions like in a biological system. So would we need to know anything more than just the sources of error/ comparison betw...

KBELTRAMI_1E

I don't know what exactly calorimeters are and I don't know what the differences are either. Can someone please explain how we're also going to use them in problems as well? There is a really good video on YouTube that may help you understand the concept: https://www.youtube.com/watch?v=nSh29lUGj00

KBELTRAMI_1E

Elizabeth Bowen wrote:Does anyone know where we can find all the powerpoints from the review sessions (/if they're all posted)? Thanks!

Quoting this because I want to see the responses :)

KBELTRAMI_1E

Viviana Velasquez wrote:You can us delta H instead of q because at constant pressure, q(p)= delta H

What is the significance of this notation? Would we be marked down for using q?

KBELTRAMI_1E

Hui Qiao Wu 1I wrote:I am not sure what you mean by intensive vs. extensive states but if you are referring to the intensive and extensive properties, they are:

Intensive
color, temperature, texture, density
Extensive
mass/weight, length, volume

Which section of the textbook is this in?

KBELTRAMI_1E

Anyone have good tips for organizing variables and memorizing which are used for different questions? This unit has very similar variables and similar equations and it's confusing.

KBELTRAMI_1E

Is it always assumed to be 1 atm? What about in a vacuum?

KBELTRAMI_1E

In the homework problem 4B.7, the answer for work is -1626. However, I got 1626. When should I know to make work negative? I think you just need to know how much work is being done on the system, but I think that means that it was going from the Surroundings to the System vs the System to the Surro...

KBELTRAMI_1E

I might be way over my head in this concept, but if the Universe is theoretically constantly expanding, how can we say that energy can neither be created or destroyed? Does that mean that matter is just expanding further into the universe and therefore further from the Earth, and consequently the Ea...

KBELTRAMI_1E

Angus Wu_4G wrote:Here's a simple website that I used that helped me understand the concept, I hope it helps:

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

I found this super helpful! thank you!

KBELTRAMI_1E

Veronica Lu 2H wrote:the bigger the kb, the lower the pkb (log properties) which also means the stronger the base

so then did Lavelle mean to say that the higher the kb, the stronger the base? because the original post here says that he stated that the higher the kb, the weaker the base. now I'm confused.

KBELTRAMI_1E

Emily Lo 1J wrote:How can you change the energy in a closed system? And does it differ with isolated systems?

Quoting this because I want to see the replies that it gets :)

KBELTRAMI_1E

How many variables would we have to be given? All but one? Or are there cases where we are only given two or three variables and we are supposed to find the remaining two? If so, what chemistry knowledge would allow for this, since traditionally in algebra we are seeking the value for a single varia...

KBELTRAMI_1E

Under conditions of constant pressure, the piston has to be freely movable, thus accommodating for the constant pressure when heated. This would mean that under constant pressure the q would be the enthalpy change or equivalent to the amount of heat added. However, under conditions of constant volu...

KBELTRAMI_1E

Pa is for acids and Pb is for bases I think

KBELTRAMI_1E

Although adding an inert gas will increase the pressure of a system, the partial pressures of the reactive gases are not changing because the volume has stayed the same. Therefore, K stays the same and there is no shift in the system. so do we not have to be concerned about the change in pressure e...

KBELTRAMI_1E

also how do you know if you add or subtract x in the C section of the ICE table?

KBELTRAMI_1E

It's not "safe" when the value is like 8.5555x10^-4 because that's too close to 10^-3. if its 2.57584 x10^-4 you should be good. he said they would make it obvious on the test though.

KBELTRAMI_1E

Can you solve for the Ka using pH? Like pKa is related to pH enough? Not sure

KBELTRAMI_1E

To calculate % deprotonation (because this is the most common factor that questions ask for), 1) solve for the x variable in the ICE table 2) put x over the initial concentration (Divide x by initial concentration: x/[R]) 3) multiply by 100 to convert that to number to a % 4) that is your % deproto...

KBELTRAMI_1E

I think that this is what Lavelle was trying to demonstrate using the Lewis structures in the water example of how pH is decided. Like H3O+ vs OH-, OH- is deprotonated and H3O+ is protonated?

KBELTRAMI_1E

mol.L^-1

KBELTRAMI_1E

yeah if you have the initial concentration of either the reactants or the products you should put that in for the I in ICE and then generally add or subtract x (since we don't know the factors) and then do the opposite to the other side under C. then just combine those for E and solve for the unknow...

KBELTRAMI_1E

then just simplify and you should have all parts to the question answered

KBELTRAMI_1E

Ronak Naik wrote:The gas law is an expression that relates P and V to concentration. Thus it allows you to convert between partial pressures and concentration of a reactant or product that is in equilibrium during a reaction.

When is it relevant to use this?

KBELTRAMI_1E

The reaction never stops when balanced at equilibrium, it just constantly flows in both directions at the same rate.

KBELTRAMI_1E

Q is just used to compare to K in order to determine which reaction will proceed (toward product or reactant).

KBELTRAMI_1E

Is anyone able to give a simple, direct description of this concept?

KBELTRAMI_1E

Unless you are given the precise change, you would just use x as an placeholder. For reactants, the change will be negative x, and for products the change will be positive x. Be sure to also account for the coefficients in the balanced chemical equation, if there is a coefficient of 2, then your ch...

KBELTRAMI_1E

It really depends on the problem. If it's not given, then just don't use them.

KBELTRAMI_1E

how do you know what is a base if it doesn't have OH

KBELTRAMI_1E

Polydentate is when a ligand can have multiple bonding sites to the transition metal. An example of this would be ethylenediamine (en) or diethylenetriamine (dien). Polydentates form chelates where the ligand forms a ring of atoms including the transition metal cations. These cations are bound tigh...

KBELTRAMI_1E

Didn't know where else to put this so how do you make a new post?

KBELTRAMI_1E

Matia Kim 1B wrote:Does a triple bond have 1 sigma bond and two pi bonds? Or is it 2 sigma bonds or something totally different?

there are never 2 sigma bonds connecting two atoms. always start with a sigma and then add pi bonds

KBELTRAMI_1E

it also depends on which one u are hybridizing, if the lone pair is on the N, I think thats sp

KBELTRAMI_1E

2 pi bonds on either side of 1 sigma bond. not sure what ur asking about lone pairs?

KBELTRAMI_1E

For number 4 how does the hybridization become sp2 if there are 4 p electrons and 2 s electrons?

KBELTRAMI_1E

Lauren Ho 2E wrote:Here's a visual that I hope helps!

what makes the sigma bonds stronger?

KBELTRAMI_1E

MingdaH 3B wrote:the shape, molar mass, and individual atomic electronegativity is generally what you'd need to determine IMF. IMF then determines boiling point / melting point, not the other way around.

where can we find this info?

KBELTRAMI_1E

You should think of this molecule in the 3d form. In a tetrahedral, no matter where you put the atoms the Chlorine atoms will always be next to each other. I can't Draw a picture on here, but just look one up it might be helpful. The lewis structure looks like u can orient the chlorines to be oppos...

KBELTRAMI_1E

any tips on how to easily calculate the angles? or are we better off memorizing them?

KBELTRAMI_1E

AArmellini_1I wrote:Because in a sigma bond the orbitals can overlap to a greater extent where as with pie bonds they are overlapping indirectly which means they can't overlap as much as sigma bond. The more they over lap, the stronger the pull

what do you mean by "overlap"?

KBELTRAMI_1E

Kate Osborne 1B wrote:Octahedral shape describes a compound with 6 shared pairs of electrons and since there are 6 bonds in SF6 it is octahedral.

the term is just misleading

KBELTRAMI_1E

it says on the syllabus that 50% in the class is a C-, is this true?

KBELTRAMI_1E

does it include the midterm topics?

KBELTRAMI_1E

id say just memorize everything you can!

KBELTRAMI_1E

Katherine Chhen 3I wrote:Since week 9 is thanksgiving break and I have discussion on Thursday, would homework still be due for that week?

maybe the monday after? let us know if u find out!

KBELTRAMI_1E

So the number of lone pairs can also determine the molecular shape of a molecule? Yes, lone pairs can influence the molecular shape of a molecule but as mentioned by the previous responses we have not gone over it yet. However, to have an idea of some examples I provided an image below that shows y...

KBELTRAMI_1E

I know that when the central atom has only two bonding pairs as far as possible, forming an 180 degree angle, it is considered to be a linear shape, but what if the central atom has lone pairs in addition to the two bonds? I was also confused about this in the homework, I think it depends on the an...

KBELTRAMI_1E

Yeah, hi, just wondering if anyone would give any tips on how to draw the Lewis Structure for the chemical compound mentioned in 3F1c. H2SeO4... The problem never asked for the Lewis structure, but I'm just asking out of curiousity's sake:) (and plus, it'd probably really help to find the solution,...

KBELTRAMI_1E

Yeah, hi, just wondering if anyone would give any tips on how to draw the Lewis Structure for the chemical compound mentioned in 3F1c. H2SeO4... The problem never asked for the Lewis structure, but I'm just asking out of curiousity's sake:) (and plus, it'd probably really help to find the solution,...

KBELTRAMI_1E

at least be able to figure them out conceptually if asked. 360/3 planes = 120 is how I think of it but make it the avg

KBELTRAMI_1E

705198479 wrote:when is will we know to calculate a formal charge, will it be noticeable in the question or are there key words

do it when drawing lewis structures

KBELTRAMI_1E

try to calculate the lowest charges overall...

#of electrons in valence shell - [# of electrons in lone pairs + (# bonded electrons/2)]

KBELTRAMI_1E

but for the names, i think so

KBELTRAMI_1E

you should be able to figure them out by conceptualizing them

KBELTRAMI_1E

If the questions asks to find the molecular and empirical formula, first try to find the empirical formula which is to covert the grams into moles that’s given for each element. Then divide each element by the smallest mole value (for empirical). Remember that the coefficient can only be a whole in...

KBELTRAMI_1E

Bonds are longer or shorter depending on the distance between the two atoms. If there are multiple bonds, there are more shared electrons, so the atoms are more closely held together and the bonds are shorter. Also, if the atoms are smaller they can be closer together, so smaller atoms also make sh...

KBELTRAMI_1E

it doesn't matter until we cover shaping

KBELTRAMI_1E

are we supposed to know this already???

KBELTRAMI_1E

its everything until section 2D??? of bonds

KBELTRAMI_1E

the middle one is the one that creates the most bonds, and also its normally always carbon if carbon is one of the elements. oxygen and sulfur are also typical centered.

KBELTRAMI_1E

make your own graphic organizer!! Use formulas as main headlines and write a checklist of things you know and things you don't know.

KBELTRAMI_1E

Parker Smith wrote:the +1/2 and the -1/2 are used to signify the spin of the electron. So if you are only drawing the arrows, you probably don't need to use the ms numbers because the arrows signify spin direction already. It depends on what the problem asks of you.

how do you know which direction it goes though?

KBELTRAMI_1E

Thank you for sharing!

KBELTRAMI_1E

On problem 1D.23 I am having trouble. How do I begin to know how many orbitals can have the following quantum numbers in an atom? The concept, in general, confuses me, not just this specific question. I believe we went over it in class. I would check google images for a diagram to be sure of the nu...

KBELTRAMI_1E

If we calculate a velocity for an electron, proton or neutron that is higher than the speed of light, should we assume we did something wrong, or is there possibility for this to be an answer and we have to say that this is "unreasonable?" I think we did an example problem like this, I do...

KBELTRAMI_1E

Tai Metzger 3K wrote:In general, the periodic table has the following trends for atomic radius:
As you move down a column, atomic radius increases.
As you move from left to right along a row, the atomic radius decreases.

Do we need to know the exact number though?

KBELTRAMI_1E

Suraj Doshi 1L wrote:Can an two electrons within the same subshell have different energies associated with them?

I thought he said something like this in class, but I don't know.

KBELTRAMI_1E

Ashley Tran 4B wrote:How are wave functions/orbitals connected to quantum numbers? I'm confused... isn't the wave function about the whole atom and the quantum number refers to individual electrons?

Not electrons but photons.

KBELTRAMI_1E

I'm not sure about quantum numbers specifically, but it all just represents the behavior of photons in different scenarios.

KBELTRAMI_1E

Isn't there an exception? I'm also confused.

KBELTRAMI_1E

Which concept are you talking about?

KBELTRAMI_1E

First use the E=hc/wavelength formula to find the energy. Then, multiply that my the mols of Na and avagadros number to get the energy for 5g of Na. After that, multiple avagadros number to the number you calculated in part a to find the energy for 1mol of Na. So avogadro's number is how you get it...

KBELTRAMI_1E

Let's talk about spin. What is even going on and how do we know if it's positive or negative?

KBELTRAMI_1E

I have this issue and it happened today for a quiz. Honestly just think of it of an assessment of how much you know and try not to anticipate questions having the purpose of confusing you. If you know things, you have the opportunity to demonstrate it. I wish I would have thought of it this way.

KBELTRAMI_1E

I'm still having some difficulty balancing equations that require more than just inspection. Is there another, possibly longer but more accurate method to balancing "harder" chemical reactions. For example: Cu + HNO3 → Cu(NO3)2 + NO + H2O All I know is you should start with the least freq...

KBELTRAMI_1E

Doesn't it have to do with when there is a quantifiable mass given and there are wave-like and particle-like properties both?

KBELTRAMI_1E

Drake Choi_1I wrote:Is it a good idea to review online modules before lectures so that I can be familiar with what is going to be lectured on? Or should I review after I have had the lecture? Thank you :)

YES this is what helps me the most!

Search found 108 matches