CHEMISTRY COMMUNITY

Gicelle Rubin 1E

That's because there isn't any change in temperature :)

Gicelle Rubin 1E

yes, you usually look at the overall rate law and see which reactants are part of it, and then match that to the elementary step which also has the same reactants. Or, the problem would give you the slow step. Only the reactants in the slow step are included in the rate law. If you see a reactant i...

Gicelle Rubin 1E

Thank you for asking, I was also wondering the same thing!

Gicelle Rubin 1E

Basically:
Enthalpy would be the the amount of heat released/gained
Entropy would be the disorder :)

Gicelle Rubin 1E

Gillian Gabrielsen2F wrote:ΔU = q+w
For this problem, q= 5.50 kJ.
Since the expansion work is done against a contant pressure, w= -PΔV
So ΔU = 5.50 kJ + (-PΔV)
ΔV= 1.846L - .345L and P = 750/760 atm (converting Torr to atm).
Hope this helps!

thank you for your explanation! :)

Gicelle Rubin 1E

It would if no heat is moving around! :)

Gicelle Rubin 1E

I just saw another post similar to this and it's SATP (298K) :)

Gicelle Rubin 1E

Valerie Tran 2B wrote:I saw this on a different chem community post but my understanding is "standard conditions" uses 298K (gases, liquids, and solids). 273K is for STP which is a subset of standard conditions and specifically refers to ideal gases.

Thank you for clarifying! :D

Gicelle Rubin 1E

As others have said, Delta G naught is at standard conditions :)

Gicelle Rubin 1E

As everyone has said, it's theoretical :)

Gicelle Rubin 1E

i definitely think going over the book will be very helpful!

Gicelle Rubin 1E

For this problem use the arrhenius equation k = Ae^−EaRT where A is the frequency factor 8.07×1011. You should convert the temperature into Kelvin from Celsius, rearrange the equation to kA = e^−EaRT and take the natural log of both sides so that your equation becomes Ea =−RTln(k/A). You can then i...

Gicelle Rubin 1E

Thanks to all the replies; They were extremely helpful! :)

Gicelle Rubin 1E

I'm not completely sure but I think it is an error

Gicelle Rubin 1E

I think that's correct! The catalyst speeds up the forward reaction by lowering the activation energy, but it also speeds up the reverse reaction by lowering its activation energy by the same factor. The catalyst wouldn't affect equilibrium because its forward and reverse effects would "cancel...

Gicelle Rubin 1E

VincentLe_3A wrote:F would be an electrophile as it would need one more to get a full octet. On the other hand, F- is nucleophile as it has an extra electron.

Thanks for giving some more information! :)

Gicelle Rubin 1E

Yep! they're sealed and insulated :)

Gicelle Rubin 1E

Hi! I believe that at absolute zero, or 0 Kelvin, a perfect crystal is the only thing with an entropy of zero. However, this is not actually possible since we cannot actual reach a temperature of 0K. Also, standard molar entropy implies that it is at standard conditions (298K) so 0K is not possible...

Gicelle Rubin 1E

i know it's repetitive but as you already know, it's 1/K :)

Gicelle Rubin 1E

greater concentration is favored :)

Gicelle Rubin 1E

Christine Ma 3L wrote:q and q_rev are both just heat terms, but q_rev refers to heat from a reversible expansion. When systems are approximated as reversible (like when we're trying to calculate the maximum work), we use q_rev.

Thanks for this! I was still a little confused from other replies ;-;

Gicelle Rubin 1E

Hi! I remember Dr. Lavelle stating that some of these are more reliable than the others, and I was wondering which ones are more accurate and why. Thank you! Hi! Out of the three methods (Hess's Law, Bond Enthalpies, and Standard Enthalpies of Formation), using bond enthalpies is the least accurate...

Gicelle Rubin 1E

It's repetitive but larger molecules have higher entropy because of their mass

Gicelle Rubin 1E

I'm having the same issue so I'm hoping someone can help answer :,)

Gicelle Rubin 1E

I'm not entirely sure because I'm still stuck on the rest of that problem. I was wondering if you were able to solve it and if so, how?

Gicelle Rubin 1E

Summer_Corona 3L wrote:For strong acids I use SO I Brought NO Clean Clothes. I don't know one for bases but Lavelle had said if the cation is from groups one or two then it's strong.

SO- HSO4
I- HI
Brought- HBr
NO-HNO3
Clean- HCl
Clothes- HClO3 or HClO4

Thanks for this, I hope it'll make them easier to remember!

Gicelle Rubin 1E

As many have mentioned, it is in relation to the energy in steam in comparison to its boiling liquid counterpart.

Gicelle Rubin 1E

Gibbs free energy (ΔG) equals the work exchanged by the system with its surroundings, minus the work of the pressure force. The best way to identify if a problem is asking you to use the equation is to see if the problem is dealing with energy work and pressure 9x out of 10 you can use Gibbs's equa...

Gicelle Rubin 1E

Thanks for asking this question. I was also confused but I'm glad there are responses! :)

Gicelle Rubin 1E

Orly Termeie 3I wrote:If Delta G is negative the fuel cell would be feasible and thus, the cell potential would have to be positive. Since the products would have a lower energy than the reactants which is favorable.

Thank you for explaining it! :D

Gicelle Rubin 1E

Someone answered this question before with: "Residual entropy is the entropy that remains after molecules stop moving at 0 degrees kelvin. The entropy lies within the orientation of the atoms of the molecule." I thought it was the clearest explanation so I hope it's also helpful for you! :)

Gicelle Rubin 1E

The N value is the number of molecules present. The base for this is the number of states that are possible for the molecules. These states can be determined by simulating the various different positions that the molecules can be in, in the system. This is crucial to the measure of entropy as entro...

Gicelle Rubin 1E

lucky for us, these are given! :D

Gicelle Rubin 1E

Hi! I'm not exactly sure if Dr. Lavelle said why in his lecture, but the way I like to think about it is that solids and liquids are held together by intermolecular forces. In order for these IMF to be present, the molecules of the solid or liquid need to be oriented a certain way so that they can ...

Gicelle Rubin 1E

Hi! You need to account for both the heat needed to melt the ice and the heat needed to raise the temperature of the melted ice/water to the final temperature. This is how I would set up the problem: heat needed to melt ice + heat needed to raise temp. of water = - heat released to lower temp. of w...

Gicelle Rubin 1E

Sophia Dinh 1D wrote:what is the difference between isochoric and isometric?

Isochoric: value of volume is constant

Isometric: measurements are constant

:)

Gicelle Rubin 1E

The learning objectives don't explicitly say to memorize standard states, but it does say that you have to recognize when a substance in its standard state. If you can do this without memorizing a bunch of standard states, that's probably easier. Here's a link to a different post talking about how ...

Gicelle Rubin 1E

The steam causes more severe burns because of the large amount of energy it takes to turn liquid water into steam. If you think about the steam as condensing when it hits your skin, then the steam must release all the energy it took to phase change into vapor, and therefore it releases a lot of hea...

Gicelle Rubin 1E

It's already mentioned but it's because the volume's value is changing :)

Gicelle Rubin 1E

Hi, I was confused about this too, but I remember Dr. Lavelle saying that if the equilibrium constant is under 1x10^-3 then you can assume that the change is insignificant, but I've read that 1x10^-4 is more accurate. It can be assumed to be insignificant if it is less than this and doesn't change ...

Gicelle Rubin 1E

As said by others, I don't believe so :(

Gicelle Rubin 1E

Jenaye Brelland 2I wrote:The -log[H+] will result in the pH. The -log[OH-] will result in the pOH. Remember that p in pH means -log. So pH is -logH+ and pOH is -logOH-.

Hi Jenaye! I'm glad to see you explanation written out! It serves as a little reminder :)

Gicelle Rubin 1E

I know it's a bit repetitive hearing the same thing but a state function means that, in order to determine its value, we only need both the initial and final state.

Gicelle Rubin 1E

Im on like my 9th attempt for this problem and still can't seem to find what I am doing wrong. I am following the same procedure as above, could someone help? My Kb=3.435x10^-5 and my pH=9.705. First you would need to find the value of [OH-] by subtracting your given pH value from 14 and then apply...

Gicelle Rubin 1E

I'm pretty sure that is correct!

(if not, please let me know ;-;)

Gicelle Rubin 1E

Q is the reaction quotient and can be used to figure out which direction the reaction will shift in order to reach equilibrium. K > Q: reaction proceeds forward, R --> P. K < Q: reaction proceeds in reverse direction, P --> R. Q = K: system is at equilibrium, no shift to either left or right Thank ...

Gicelle Rubin 1E

Hannah Biju 1E wrote:If there is formation of an acid (H3O+), then you should use Ka. If there is formation of a base (OH-), then you should use Kb.

Thank you for your clarification! I had totally forgotten about this!

Gicelle Rubin 1E

Q and K don't represent the same number. K is a constant that stays the same (unless you change the temp) and shows you the ratio of the concentration of products over the concentration of reactants. Q actually can help you determine if a reaction is at equilibrium and if it isn't how it will shift...

Gicelle Rubin 1E

I'm also struggling on the application of the quadratic equation. I'm not sure how to use it correctly or when to use it :,)

Gicelle Rubin 1E

As many before me have said, it is a constant :)
R = 8.3144598 J/mol·K

Gicelle Rubin 1E

Mohamed Mido wrote:Any NOF atom that has lone pairs can H-bond. Alos all hydrogens bonded to NOF can H-Bond. It can be tricky because Hydrogen atoms that are bonded to Carbon can't H-bond, but NOF atoms bonded to Carbon can, so you'll have to remember that.

Thank you for this!

Gicelle Rubin 1E

I remember hearing that since O is pulling towards H, it means a weak bond. As you mentioned, their electronegativity is involved :)

Gicelle Rubin 1E

I myself am not entirely sure. I just know it has something to do with their electron configuration. Thank you for asking this question since I was also wondering the same thing!

Gicelle Rubin 1E

The anion has to have more than one h atom :)

Gicelle Rubin 1E

this is a bit of a dumb question but what exactly do we mean when we say something is delocalized? i've seen it in a couple of posts and im a bit confused as to what that exactly means Hi the term delocalized is used to refer to an electrons activity! so if it is delocalized, it means that it is no...

Gicelle Rubin 1E

connie ma 2B wrote:to clarify what someone else said, complete neutralization only occurs if its a strong acid reacting with a strong base. if its strong/weak or weak/weak then i dont think complete neutralization occurs.

Thank you for this! I found it much easier to understand.

Gicelle Rubin 1E

Well it depends. If you remember earlier in the quarter, when we first reviewed unhybridized orbitals, we learned that p orbitals have 3 different orientations-- px, py, and pz. Each p orbital was on a different axis. The reason the unhybridized p orbital was perpendicular rather than in plane was ...

Gicelle Rubin 1E

Because electrons are delocalized (meaning they are not bound to just one location, for example, a double bond), this makes the molecule more stable. Resonance structures allow for different bond configurations between atoms in a molecule. The electrons have "different options" in terms o...

Gicelle Rubin 1E

I always keep as many decimal points while I'm working on the math and once I've got my final answer, I focus on sig figs :)

Gicelle Rubin 1E

coordinate covalent: 1 atom donates BOTH electrons

regular covalent: 2 atoms share 1 electron

Gicelle Rubin 1E

CesarLec1 wrote:I believe that for our purposes, when we see a molecule with 6 carbon atoms, it will most likely be in a ring structure

Thank you for explaining this, I did not know that was the case! :)

Gicelle Rubin 1E

Hi! As the charge become more positive, the ionic radius usually decreases. This is because there are fewer electrons in the atom. As there are fewer electrons, the electrons are pulled closer to the nucleus of the atom. When an ion is more negative, the ionic radius increases because the electrons...

Gicelle Rubin 1E

jordanginyard_ wrote:What is a good calculator to use for chemistry? what's a good periodic table because sometimes I get the problems wrong with the numbers that are used on the periodic table?

I currently use the ti-84 just because it's the one calculator I'm familiar with! :)

Gicelle Rubin 1E

VSU_2G wrote:As others have said, I believe they're the same thing! Free radicals are involved in oxidizing elements, and I feel like an element with an odd number of electrons would want electrons from other substances, so I believe they are interchangeable terms.

Thanks for the clarification!

Gicelle Rubin 1E

It's a salt in it's liquid state and as many have said, it has a low melting point :)

Gicelle Rubin 1E

I use the electronegativity trend and shape to help me find out if the molecule is polar. So, if a molecule is polar, that means one side is hogging the electrons more than the other. So if more electronegative atoms are on one side of the molecule, then it is polar. If the electronegative molecule...

Gicelle Rubin 1E

Is there a specific benefit for hybridization? Why does it occur in the first place? Hybridization occurs to fix the imbalance in the energy levels of the electrons when an atom bonds using electrons from different orbitals. This will result in a more stable molecule! Thank you for clarifying! I di...

Gicelle Rubin 1E

I just remember that the smaller the difference in electronegativity, the more covalent it is! :)

Gicelle Rubin 1E

I'm working on this too because I get confused at times, but the Lewis structures (of course) help me with identifying the Lewis Acids and Bases. If a molecule for example has lone pairs to give would be examples of bases. Central atoms that are electron deficient (maybe having a positive formal ch...

Gicelle Rubin 1E

I'm already scared for our final knowing how I did for our second midterm... ;-;

Gicelle Rubin 1E

I hope we won't have to know what they are based on their names because I'm confused on how to do that, but I don't think we'll need to because he hasn't taught us. I agree but thankfully many have mentioned that we are not required to memorize them and that they will be provided for us should it c...

Gicelle Rubin 1E

I also had the same question. Thank you for asking!

Gicelle Rubin 1E

To find the oxidation number of ClO4- you can use a simple equation. Assuming oxygen will have a (-2) oxidation number and knowing the total charge of the molecule is (-1) you can write the equation Cl+4(-2)=-1. Solving for Cl gets you Cl=7, which means the oxidation number for Cl is +7. I apologiz...

Gicelle Rubin 1E

An element can have an expanded octet if its energy level has access to a d orbital. For example, the elements in the 3rd period have access to the 3d subshell, so elements like Phosphorus and Sulfur can have more than the traditional octet. However, elements in the second period like Nitrogen or O...

Gicelle Rubin 1E

darchen3G wrote:Single bond: 1 sigma
Double bond: 1 sigma 1 pi
Triple bond: 1 sigma 2 pi
Quadruple bond: 1 sigma 2 pi 1 delta

Thank you for this!!!

Gicelle Rubin 1E

Brian Bui 2A wrote:As others said, they are interchangeable! However v (Greek letter) for frequency has a little curve on the left while v for velocity is just straight, if that helps. Very nit-picky details!

Thanks for this! I probably would not have noticed that tiny detail.

Gicelle Rubin 1E

As everyone has said, as long as you multiply both by the same number, you should be fine! :)

Gicelle Rubin 1E

Another good tip for scientific calculators is to set it SCI mode. Usually, the default is on FLO, but SCI shows results in scientific notation which saves time from homework and test questions. I believe our week 0 sapling optional homework noted this. I didn't know this was a feature! Thank you f...

Gicelle Rubin 1E

Yes!! If I don't add parenthesis in some occasions, it gives me a totally wrong exponent and it messes everything up!

Gicelle Rubin 1E

When multiplying two numbers in scientific notation, multiply their coefficients and add their exponents. When dividing two numbers in scientific notation, divide their coefficients and subtract their exponents. If you remember from math where we were taught how to multiply and divide with exponent...

Gicelle Rubin 1E

Hi! I am pretty sure mass has to be in kg. In examples where I'm given grams, I convert to kg before using any equation.

Gicelle Rubin 1E

Hello! Conceptually, constructive interference occurs when the troughs line up with each other, and when the peaks line up with each other. This results in constructive interference because in either case, the amplitude will increase . And because the amplitude increases, this signals that construc...

Gicelle Rubin 1E

Edward Tang 2E wrote:Actually I dont think you need the wavelength equation. Just do e=(c/wavelength)*plancks to figure out the energy of the photon, convert that to eV by dividing 1.602e-19 and you're good

Literally thank you so much for this. I've been struggling with a similar question the entire week.

Gicelle Rubin 1E

What I normally do is use the entire number from the periodic table and after I'm done with calculations, I round. :)

Gicelle Rubin 1E

Hi! I usually put the 2 units I want to convert into a fraction. For example, I know that 1m=100cm, so the fraction can be \frac{1m}{100cm} or \frac{100cm}{1m} . Because the denominator and numerator are the same, both fractions equal to 1. Then, I can multiply a value by this fraction, and cancel ...

Gicelle Rubin 1E

They're electron pair donors!

Gicelle Rubin 1E

Thankfully it's a multiple choice midterm and if I remember correctly, my TA said there weren't going to be too many questions.

Gicelle Rubin 1E

Thank you for asking this question! I have been looking for answers for some time now!

Gicelle Rubin 1E

You actually did it correctly!! I also had my doubts about my rounding at first.

Gicelle Rubin 1E

Nope! It's not going to be on our midterm (thankfully)!!

Gicelle Rubin 1E

I personally just plan on working on practice problems and rewatching the video modules since those really seem to help me. I'm also going to try to make time to attend workshops before my midterm. Good luck studying!!

Gicelle Rubin 1E

I've found out the hard way that it's best not to round until we are finished with our problem. If we don't, the answer might be off.

Gicelle Rubin 1E

Hi there! You are correct, the wavelength/frequency did not change. It is the photons that affect the brightness of light, so it increased.

Gicelle Rubin 1E

Hi! I personally do not really have a particular order I follow when I'm balancing chemical equations. However, I have heard that you should first start off with the element that is repeated the most.

I hope that helps!

Gicelle Rubin 1E

Hi Heather! I also have some trouble with sig figs but I remember someone shared this website so I hope it help you as much as it helped me!

http://chemistry.bd.psu.edu/jircitano/sigfigs.html

Gicelle Rubin 1E

Hi there! For the example, CO4, the correct answer would be:

C= 1 and O=4

simply because there is no coefficient next to carbon the same way there is one for hydrogen.

Gicelle Rubin 1E

Hi! I remember when I saw this problem and was completely overwhelmed but it's actually a lot easier than it seems! To find the molecular formula, simply count how many of each there are for C, H, and O. Upon counting, you'll see you have C6H8O6. To find the mass of the compound, you have to multipl...

Gicelle Rubin 1E

After reading some of the replies, I'm afraid I have a silly question.
People are saying to "multiply 0.325 with 590.1g" but my question is what they did to get 0.325 and why.
Thank you!

Gicelle Rubin 1E

Hi! So, what I usually do is I try to balance the element that there is more of. Afterwards, I sort of "wing it" and try different numbers until the equation is balanced. I know it's not the best method because it requires some time but I'd like to hear other ways to do so! In regards to k...

Gicelle Rubin 1E

Hi Jenaye! I literally was so confused as well when I was working on the Sapling homework not too long ago. But riding off of what others have said, the numbers are important if they're between 2 integers. However, I am still having some trouble understanding the decimal rule.

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