CHEMISTRY COMMUNITY

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Hi, great question its called a frequency factor or pre exponential factor and it will always either be given to us or will cancel out in the equation.

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Hi, I think a bomb calorimeter is used specifically for when you want a completely isolated system like when doing a large combustion experiment. So I'm guessing you would not want the products to blow you or the calorimeter up and so you we keep it isolated.

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Hi guys, if you ever want to remember the letters for the element helium just think of this joke

How do you laugh at a Helium Joke?
He He He

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Hi, I haven't tried this specific problem but I do know that the book sometimes has errors. I'm pretty sure that on the bruin learn page there is a model that has a link to a page that tells which problems the textbook solutions have errors in.

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Hi, I was wondering if someone could explain to me how delta u and delta t are effected when a system is isothermal.

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Hi, when is it okay to take n out of the q=nc(delta T) equation and when do you have to keep it in?

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Hi, I saw joke online and I just had to share:
H2O is the formula for water, what is the formula for ice? H2O cubed
Isn't that so funny!!

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Hi, I'm pretty sure the standard reduction potential of H2 is zero. I'm not sure if this is the only one equal to zero and it acts a baseline or if there are other things that also have a standard reduction potential of zero.

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Hi, the first step is determining the order of each of the three A,B,C. You do this by setting up a rate law with one of the experiments with the exponents on top as three different unknowns and then you divide by another rate law (putting variables for exponents again) from another experiment where...

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Hi, I was wondering what the relationship between pH and Pka is and how you can use those values to know whether the predominant species is charged or neutral?

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Hi, I was wondering if anyone has any tricks for remembering which half-life equations go with each reaction order because I keep on getting them confused.

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Hi, what elements do we always know the oxidation numbers of and what elements do they change depending on what they are bonded too. And also what exactly does the oxidation number tell us.

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Hi, I totally get how this is confusing but I think to set up the second equation you have to have both sides of the equation in the same state so first you have to see how much energy it takes to make ice at zero degrees to water at zero degrees. The reason you can "heat" up ice without c...

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Hi, great question I was wondering about this too. I heard in a workshop today that no to steps are exactly the same speed so you will always have to use only one slow step. However, sometimes you may substitute out intermediates.

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Hi, how do you do determine the rate constant if you are given experimental data in a table?

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Hi, what is the difference between unique, differential, and integrated rate laws?

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Hi, I am really confused on what to include in my half reactions for question 4. What do I do with the other molecules and other elements within one molecule that were not oxidized or reduced?

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Hi, I am not completely sure but I think that gibbs free energy is telling us which side a reaction tends toward aka the side with the lower energy. So because at equilibrium the reaction is not going towards either side this would make delta G equal to zero. I think the idea of no work being done a...

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Hi, well ok I am also confused about this but I think that this equation in part comes from the fact that in an isothermal reaction temperature is constant so delta t would be O and we know that delta U and temperature are related so then it would make sense that delta U is also zero. In terms of ap...

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Hi, I have been struggling with this too. Something that helped me a bit was rewriting the equations I've been using frequently on a separate sheet and organizing then by what they are solving for and what variables they use. I'd love tips if anyone has found a better way though.

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Hi, can someone explain to me exactly how I can visualize the concept of degeneracy and how to understand the equation for it because I keep getting a bit confused.

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Hi, in one of the achieve questions for thermodynamics the hint told me to use the equation q=mC(deltaT) however, when I looked on the equation sheet the only thing I found was the equation q=nC(deltaT). I only had the mass in grams of an unknown gas so I used m, but I was wondering if m and n are i...

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Hi, I think this is because systems naturally move towards more disorder. For example you naturally make your room messy overtime so the equilibrium of you room is going to messier aka have more entropy than if you worked really hard to clean it up aka not at equilibrium

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Hi, in lecture when he mentions reactions happening in a vacuum what exactly does that mean in this context and how does that affect the reaction?

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Hi, I am a pit confused on the difference between Delta U (change in internal energy) vs Delta H (change in enthalpy) can someone please explain the difference.

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Hi, I know is a workshop a UA told me one way could be to draw out the lewis structures and see if bonds we broken (aka need energy) or formed (aka released energy). So then if a bond is broken it would be endothermic and vice versa. However, I think this only works for like super simple reactions b...

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Hi, I think it would be an exothermic reaction because burning the gasoline provides energy to power the car. So even though it doesn't directly seem like it produces heat like a fire, it still produces energy because then the car is able to drive. To make a car move we need energy and so because wh...

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Hi, in class he talked about how steam engines related to the concepts we are currently talking about in class. However, I don't really understand how a steam engine works so I was wondering if someone could explain how a steam engine works and how it relates to what we are learning.

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Hi, in class we went over the equation delta U = delta H - P delta V. I was very confused on what that equation is saying and also I was wondering what exactly delta U stands for in the equation. Can someone explain this. :)

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Hi, state properties are things where you can add different parts of the reaction together (or subtract different parts) without it mattering. He used the example of saying where two hikers started and ended and you can find those values without out knowing the trail they took.

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Hi, I remember him talking about how endothermic reactions are still measured at a constant temperature but I am confused because don't endothermic reactions release heat? Can someone explain this.

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Hi, I think I remember him talking about the fact that we are not able to measure how much energy it takes to break one bond of a double bond. I think this is related but I'm not completely sure.

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I think I remember him saying in class that sodium and potassium don't effect the pH and I was confused about why that is? Why don't they or did I miss hear?

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Hi okay from my understanding a temperature change will change K. And Q is just the ratio of products and reactants at any given time so you use Q as a benchmark to see how K changes. So I think that question 7 assumes that Q is the old equilibrium constant and you are comparing it to K the new curr...

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Hi, one thing that has helped me with the quadratic formula is making sure I plug all the numbers into the entire equation before simplifying or solving anything. Another thing that helps me is making sue I balanced the equation with the right coefficients and that I moved them over to the K equatio...

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Hi, I was wondering if anyone has a list of all the different equations you need to calculate PH and POH from H30+ and OH- concentrations?

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Hi, in discussion today we talked about reactions with strong acids. I remember people saying that strong acids complete disassociate and I was wondering what this means and if it is always true?

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Hi what should I think of when I see a small K versus a large one, what does it mean in terms of reactants and products

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Hi I think when delta H is negative the reaction shifts towards the reactants when temperature increases because it is shifting towards the place with the higher enthalpy

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Hi, I think the difference has to do with Kc only referring to when the reaction is in equilibrium whereas Q can be refering to anytime during the reaction. At least that is what I think.

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Hi, I am having a lot of trouble with the achieve, and I was wondering what happens if you end up getting an x^2 as well as an x on the bottom of your fraction or am I just doing something wrong in setting it up.

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Hi, I was wondering the exact same thing! Does anybody know the answer?

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Hi, I was wondering what makes cis-platin a better cancer drug than trans-platin, I am still a little bit confused on this.

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Hi, is there any tricks to knowing if an acid or base is strong or weak based on how its written or how the lewis structure looks or is memorizing the only way?

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My brother is super negative and I'm super positive but we never want to be apart. We have an ion-ion intermolecular force relationship.

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Hi, I think it is because Cl is more electronegative than Br and I so it delocalizes the electrons on the oxygen the most and this makes the anion version of it more stable. Therefore it is the most willing to give up a proton.

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Yeah, adding on to this I think that when a molecule is more polar the electrons are more delocalized throughout the molecule and when electrons are more delocalized this makes this makes the anion version of the molecule (ie the molecule without the proton) more stable. Therefore it is more likely ...

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Hi, I remember at a UA session I went to last week the UA told me that we only had to worry about strong bases and acids in 14A and that we would learn how to do calculations with week ones starting in 14B but I'm not completely sure.

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Hi, I think that we are supposed to memorize the different angles because its something he went over in class. I could be wrong tho. I am going to make flash cards to help me memorize the angles that correspond to different shapes.

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Ok hi so I think this follows because the molecules are most likely to give away their proton if they will be stable after they give it away and a strong acid means the molecule is super likely to give away their proton. So you will be more likely to give away your proton if your anion afterwards wi...

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Hi, does anyone have any tips or tricks for remembering bond angles based on shape?

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Hi, does anyone have any tips or tricks for remembering molecular shape based on the lewis structure?

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Hi, when a molecule has both a cis and a trans configuration how do you know which version is more common or more stable, and why?

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Hi, I've noticed that sometimes when you create hybrid orbitals there are already two electrons in the S orbital but when it becomes an SP orbital you only have to up-spinning electron, I was wondering what happens to the down-spinning electron? Or if I am just mis-understanding hybrid orbitals.

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-Hi, on Achieve there was a question that said if X in the formula H2CCXCH2 is and even number all the hydrogen atoms in that molecule will be coplanar. I didn’t understand this at all and I was wondering why that was?

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Hi, ok I am not completely sure but I think the the two lone pairs of electron density are repelling the two bonded electrons . So, the lone pairs wouldn't disappear they would just push the bonds down from linear into bent, does that make sense?

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Hi, I am confused on about exactly what a pi bond is. I think that I remember him saying in class that a double has a pi bond. Is there a way to know which bond in the double bond is the pi bond?

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Hi, I'm not completely sure but I think that because acids are electron acceptors, they would have a positive charge because that means they want more electrons. And then bases would usually have a negative charge that means they have too many electrons so they want to give some away.

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When trying to figure out the nitrite ion Lewis structure how do we know if it has one or two oxygens within its structure?

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Hi, I think that if one molecule has a partial charge (dipole moment) its positive section can pull electrons from another molecule towards it and give that molecule that wouldn't normally have a partial charge a temporary partial charge. Or negative could push away. At least that is how I imagine it.

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Hi, I think the reason that the oxidation number is different with fluorine is the only element on the periodic table more electronegative than oxygen. Meaning that instead of taking electrons from another element, oxygen will have electrons taken from it. I think this would make its oxidation numbe...

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Hi, does how many lone pairs a molecule have connect to what the shape of a molecule will be?

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Hi, How does polarizing power relate to boiling/melting point?

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Hi, great question! I think it has something to do with the D orbital elements because as we learned lasT unit the D orbital can hold up to 10 electrons. I am not sure it that is the entire explanation.

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Hi, I was wondering if there was a way to connect electronegativity to the periodic table, like is there a pattern or a trend?

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Hi, I am confused on what exactly polarizability means and how to connect in to low/high electronegativity?

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Hi, great question! I think formal charge has something to do with how many electron/bonds and atom has around it versus how many it wants to have to get an octet. If someone could explain more that would be awesome?

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Hi, I'm pretty sure it represents the minimum (uncertainty in the momentum )times (the uncertainty in position) so if you know the uncertainty for one of those two you can plug it in and isolate for the other.

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Hi, I am wondering if there are any tricks to drawing the lewis structure of big molecules? I feel like there are so many different ways to arrange the molecules?

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Hi, this is such a good question! The exceptions in the table are at the 3d4 line and the 3d9 line of the periodic table. You can think of elements here as greedy so if the d block has 4 or 9 it will steal one from the 4s block and so the answer would be 4s1 3d5 for example.

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Hi, can anyone explain to me why 4s fills before 3d even the 4s is like further away from the nucleus?

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Hi, I am super confused about what Black Body Radiation even is and how it relates to the rest of what we are learning in class?

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I think its because objects with a larger mass often are too big to exhibit detectable wave-like properties. Therefore the uncertainty principle isn't really as applicable? I'm not completely sure though.

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Hi, Okay I was confused about this as well but I was told that if the kinetic energy from the light of the photon is equal to the work function(the amount of energy needed to eject an electron) then the electron will get ejected it will just move really really slowly towards the detector. Does this ...

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Hi, sorry but I am really confused about what blackbody radiation is and how it relates to what else we've been learning in class?

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Hi, what is the difference between an orbital and a sub-orbital. Also, I am very confused on how to tell which level electrons are in, like what is the process?

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Hi, I agree with what was said above and I was also wondering what Plank's constant is like a constant of. For example, I understand the speed of light is a constant because that is how fast light goes but what is Plank's constant a constant for?

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Hi, yes I'd just like to add on that I think both principles require the assumption that it is behaving like a wave.

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Hi, thanks for this explanation, in the context of that multiple choice question what would it mean for "the extent of change to decrease"?

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Hi, I don't understand what an electric field is and how it can change. Here is an example of a multiple choice question/ answer talking about an electric field that I don't understand.
https://drive.google.com/file/d/1sNJPXR ... sp=sharing

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Hi, I am very confused about this slide from the lecture. I don't understand what the Balmer Series is, what the equations on the slide me, and how it relates to light/electrons.
The picture the slide is in this link:
https://drive.google.com/file/d/1Hw5N7p ... sp=sharing

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Hi, I was wondering if the step up sessions during each week covered the same material (ex. 1 worksheet per week). Or is each session unique?
Thanks.

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