CHEMISTRY COMMUNITY

Simi Kapila_3E

The more common rule is to use when K<10^-3, that is what most sources say is the when it will become negligible, so I would stick to that.

Simi Kapila_3E

The week before the midterms, I make myself do all of the assigned textbook problems, and then re-do any of the ones I got wrong the first time, because he usually puts at least a few textbook problems in the midterms. So I think it is definitely work practicing those, as well as re-doing any ones y...

Simi Kapila_3E

Yes, he said typically we will be using atm and bar to calculate Kp, the other units I don't believe we should be using.

Simi Kapila_3E

There is much more water than the other molecules in the reaction, so we take it out because it would cause the other molecules to become negligible. Also something else that might help you think about it, water is a liquid and we never use pure liquids when solving any equilibrium constant.

Simi Kapila_3E

n=moles and V=volume, which can be liters. And since concentration is mol/L, n/V can mean the exact same thing.

Simi Kapila_3E

Yes, Q is used anytime the reaction is not in equilibrium and K is only used when the reaction is in equilibrium. You can use the Q value to comparatively to the K value, to see where you are in the reaction (to see if it needs to shift right or left).

Simi Kapila_3E

when you take a reverse reaction, you will inverse the K value (1/K) to get the new K value.

Simi Kapila_3E

I believe he mentioned in lecture that it should be in Kelvin, and most likely we should know how to covert from celsius if the problem gives us temperature in that unit.

Simi Kapila_3E

When whole equations are being multiplied or divided by a value, then that value becomes an exponent to the previous K value. For example if an equation was multiplied by 2, then the new K value would be K^2.

Simi Kapila_3E

Use Kp when all products and reactants are in the gas phase, and you Kc in any other circumstance. But remember, you never include solids and liquids when determining the equilibrium constant, only molecules in aqueous or gaseous form.

Simi Kapila_3E

Make sure you count up all of your valence electrons on your atoms in the molecule. Then add any electrons if you have anion (the number of electrons you add is equal to the charge of your anion) or subtract any electrons if you have a cation (again the number of electrons you remove is equal to the...

Simi Kapila_3E

The atoms in the molecule with the highest electronegativity will pull the electrons more, creating a negative dipole at that atom. And since that atom is pulling electrons, other parts of the molecule will have a positive dipole since electrons are being pulled away from them. To draw the arrow, th...

Simi Kapila_3E

Ionic molecules are considered to have an electronegativity difference of 2. Since aluminum has an electronegativity of 1.61 and chlorine has an electronegativity has a difference of 3.16, their difference isn't big enough, and wouldn't be considered an ionic bond.

Simi Kapila_3E

A coordination number relates to how many bonds the TM makes. Since there are 4 Br, you can assume Fe bonds with 4 Br and forms 4 bonds. Thus, creating a coordination number of 4.

Simi Kapila_3E

The only one I remember being in his lecture was cisplatin. And on the course outline it says we should know chemotherapy drugs, so it might be helpful to remember this for the final.

Simi Kapila_3E

Jason_Glass_3H wrote:He said our grade would be a raw score right? Like he wouldn't curve it?

Yeah he never mentioned anything about a curve, nor has my TA, so I wouldn't count on it.

Simi Kapila_3E

I don't think we will have to know pH for specific foods or drinks, but I think you should probably know common acids and bases. Also he mentioned that basically everything we consume is acidic, if that helps.

Simi Kapila_3E

I believe it will be fairly similar to the two midterms, just with more questions, I think 30 this time, and it will be cumulative . And most likely we will be using a secondary device for the test.

Simi Kapila_3E

My TA was telling us that if there are any discrepancies between Dr. Lavelle's lectures and the textbook, or some other source, always follow what Dr. Lavelle is saying.

Simi Kapila_3E

Yes, you're right, since Br is a bigger atom, it is farther away from H, making the bond length longer, and thus creating a weaker bond. Since it is a weaker bond, it is easier to dissociate the molecule and create hydronium ions.

Simi Kapila_3E

It is considered an sp3 hybridization because it has 4 areas of electron density, 3 bonds to oxygen and 1 lone pair. Sp3 orbitals indicate that there are 4 areas of electron density, one provided by the s and 3 others provided by the p.

Simi Kapila_3E

Since pi bonds are bonded side to side, if one half tries to rotate it will break split from the other side. Sigma bonds can rotate because they are bonded at one point and they won't break.

Simi Kapila_3E

CHI3 has a higher melting point because it is bigger, and thus more polarizable. Additionally, when atoms are bigger, they have stronger london dispersion forces. since I is bigger than F, CHI3 has stronger london dispersion forces than CHF3, and thus is harder to dissociate and harder to melt.

Simi Kapila_3E

Delocalized pi bonds occur when a structure has resonance. They are considered delocalized because they do not have a single permanent location, due to the fact that the actual molecule is usually a mix of the resonance structures.

Simi Kapila_3E

I don't think he taught us that, and I believe he mentioned we would only have to know s and p orbital hybridizations for the final.

Simi Kapila_3E

Atoms who have a smaller difference in electronegativity tend to have more covalent character. Also atoms that are more polarizable can create more covalent bonds, because they can distort the electron distribution.

Simi Kapila_3E

In this example, the larger molecules have stronger london dispersion forces, making it more difficult to dissociate than the smaller molecule, the one with weaker london dispersion forces, thus the larger molecule has a higher boiling temperature.

Simi Kapila_3E

My TA told me it will be cumulative, so we will have to know everything back to the first week.

Simi Kapila_3E

I think the easiest way to calculate would just be the valence electrons -(number of bonds or lines) - (number of lone pair electrons or dots) to give you formal charge

Simi Kapila_3E

Technically we have Thursday and Friday off, so I would expect to have lectures Monday and Wednesday.

Simi Kapila_3E

Feeling really prepared helps me. Usually doing as many practice problems as you can, so you feel like there is nothing you haven't seen. But besides that, you could try going for a quick walk before the test, or doing some deep breathing to help calm your nerves.

Simi Kapila_3E

I believe, he does want us to remember the name, and most likely the bond angle. He was basically saying from his lecture you can intuitively figure out the name of the structure based on its shape. I'm not completely sure about the bond angles. I think most of them are pretty straight forward, besi...

Simi Kapila_3E

Yes they do count, you have 4 sig figs since the 0's come after the decimal place.

Simi Kapila_3E

That's right, the sum of all the formal charges in a molecule will give you the overall charge for that molecule.

Simi Kapila_3E

Resonance shows that there are multiple structures for a single molecule. However, the way we draw resonance structures isn't completely accurate, and the actual structure is usually a blend of the resonance structures, which provides the molecule with more stability.

Simi Kapila_3E

It is during week seven whenever you have your discussion section.

Simi Kapila_3E

I think he said we would only be responsible for knowing s, p, and d orbitals for electron configuration. I don't think we would have to know the f orbital.

Simi Kapila_3E

When an atom loses its first electron, the effective nuclear charge has a greater effect on the other electrons. Thus, they are held more tightly to the atom, and they require more energy than the first energy to be removed from the electron

Simi Kapila_3E

Definitely give yourself some breaks. Your brain can easily get fried staring at a screen all day. Also I would recommend exercising, or just going for a walk. Personally, I always feel really refreshed after I go on a run. But anything that helps clear your mind. Whether that be just going outside ...

Simi Kapila_3E

I don't believe there is a way to determine the spin, at least not where we are yet. I think it is just important to know that those are the only numerical options for the spin quantum number.

Simi Kapila_3E

The elements that do no coincide with the octet rule are H, He, Li, and Be, they cannot get a full valence shell.

Simi Kapila_3E

Yes for us, c will always be synonymous with speed of light.

Simi Kapila_3E

eV stands for electric volts. The conversion is 1 eV=1.60218x10^-19 J

Simi Kapila_3E

I don't think there is a way to access the lecture offline, since they are posted on CCLE, sorry.

Simi Kapila_3E · Re: Homework due date It's due 12:59 pm on Sunday, not at the end of Saturday.

It's due 12:59 pm on Sunday, not at the end of Saturday.

Simi Kapila_3E

I really haven't heard anything about graphs. My TA told me it would be a mix of computational and conceptual questions, so I'm pretty sure there won't be graphs.

Simi Kapila_3E

Check the question, it will most likely tell you which units your answer should be in. But make sure when you are doing your calculations that you are using the standard meters for it, and only cover to nm after you have finished your calculations.

Simi Kapila_3E

We aren't allowed to bring any note sheets we make ourselves. However, I believe he sent us an email with two page attachments that we are supposed to print out. One is a periodic table, and the other is an equation and constants sheet. Also we are not allowed to write anything on these sheets befor...

Simi Kapila_3E

Hey I kind of have a similar question, but couldn't figure out how to make a new post. Does anyone know if there are answers to the questions in the textbook to check if we are doing them correctly?

Simi Kapila_3E

I don't think it has ever been specified how many to use. Bu the more you use, the more accurate your answer will be. So if possible, I think it would be better to use more.

Simi Kapila_3E

Yes, they mean the same thing, it is just two different ways to say it.

Simi Kapila_3E

Reactant and reagent mean the same thing. They are just two different ways to say reactant.

Simi Kapila_3E

For studying I would definitely recommend watching the modules he posts, and doing the post/pre-assesments that go with them, because they have practice problems and you can get more experience by doing them, and sometimes in those videos he will include things he doesn't include in the normal lectu...

Simi Kapila_3E

I think you should try to stick to a paper and pencil, because if you are using device for the exam they won't be able to be sure if you are being honest. However, you could talk to your TA and see with them if it's ok, because our workspace will be monitored during the exams anyways.

Simi Kapila_3E

Usually in a word problem they will indicate whether a value is a wavelength or frequency. However, you can also tell by the units given. Frequency will always be in Hertz (Hz or s^-1) and wavelength will usually be given in nanometers (nm) or possibly some other variation of meters.

Simi Kapila_3E

I would check out the audio-visual topics he has on his website, they are very informative and they go over all of the fundamentals in detail. They also have pre-assessments and post-assessments, which will help you to discern what you need more practice with.

Simi Kapila_3E

In his examples, he usually uses 4 or 5 sig figs (usually 3 numbers after the decimal place), so I would say stick to that amount.

Simi Kapila_3E

I believe he said that you should be able to solve for any of the variables in the equation by substituting the numbers given in the problem in for the correct corresponding variables.

Simi Kapila_3E

An extensive property depends the on the amount of substance. Volume is an extensive property, because if you have more of a substance, then its volume will be greater. An intensive property doesn't depend on the amount of substance that is present. Density is an intensive property, because if you k...

Simi Kapila_3E

I think when balancing equations, you should start with balancing the element that occurs the least in the chemical equation, and then go on to balance the other elements in the equation.

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