CHEMISTRY COMMUNITY

kristinalaudis3e

they are necessary to prevent buildup !

kristinalaudis3e

it's added when on any side of the cell there is no conducting metal

kristinalaudis3e

yes they should be given to you through a chart!

kristinalaudis3e

molar heat capacity is the amount of energy needed to raise the temp of a mole of substance by 1 degree. specific heat capacity is the amount of energy needed to raise the temp of a gram of a substance by a degree

kristinalaudis3e

it lowers the activation energy so that the reaction can occur faster!

kristinalaudis3e

think about physically what is happening in the equation. exothermic means it releases energy while endothermic means it absorbs!

kristinalaudis3e

enthalpy is the change in heat within a system. heat is the transfer of energy between systems.

kristinalaudis3e

high reduction potential means its good at oxidizing.

kristinalaudis3e

Zero order reactions are associated with he first and first order reactions are associated with the second!

kristinalaudis3e

the question usually gives you that info!!!

kristinalaudis3e

look at the units given and find the equations that fit that!

kristinalaudis3e

K is the Boltzmann constant which is on the equation sheet

kristinalaudis3e

F is an electrophile because it needs an electron. meanwhile, F- is a nucleophile because it has lone pairs to donate.

kristinalaudis3e

nucleophiles can donate lone pairs while electrophiles want to gain an electron

kristinalaudis3e

An Ox and a Red Cat helped me in high school!!

kristinalaudis3e

this one helped me all throughout high school as well! thank you for sharing!

kristinalaudis3e

no they dont need to be part of the calculation

kristinalaudis3e

OIL RIG is one that has helped me through all of high school!

kristinalaudis3e

The salt bridge connects both sides so as to allow the ions move from each side to the other.

kristinalaudis3e

I like to just think of the complete opposite. oxidizing agents are being reduced so they gain e-. therefore, reducing agents lose e-.

kristinalaudis3e

it measures disorder in a system!

kristinalaudis3e

you have to convert into J/K!!

kristinalaudis3e

yes they do bc they are all state functions

kristinalaudis3e

∆S = nRln(V2/V1) is the equation I used. You are given multiple parts of this equation already so you can just solve it for ∆S

kristinalaudis3e

d is for derivatives!

kristinalaudis3e

Thank you for all of these! they really helped in helping me understand the different ways work can be applied to a system.

kristinalaudis3e

I believe in his lecture, Dr. Lavelle described the universe as an isolated system as there is nothing outside of it and no matter or energy is able to be exchanged.

kristinalaudis3e

I really appreciated this new perspective of what entropy is as what I assumed it to be was randomness as discussed in lecture!

kristinalaudis3e

A closed system does not allow for an exchange of matter. Think of “closed doors” as nothing comes in!

kristinalaudis3e

A way that helps me remember that work done by the system is negative is that the system loses energy just as in any subtractive property, and vice versa, work done onto the system is positive as it gains energy in an additive property

kristinalaudis3e

during compression, reactions favors the side with the least amount of moles, so in this example it would shift to the left.

kristinalaudis3e

endothermic reactions need heat added to break the bonds, but that means it'll favor the products because breaking the bonds makes products.

kristinalaudis3e

pKw will always be 14 because it is a constant!

kristinalaudis3e

if the reactants require more energy to break the bonds compared to the products, then it is endothermic. exothermic reaction have stronger bonds in the products.

kristinalaudis3e

high to low enthalpy means that it is exergonic and releases energy, which means that it would favor reactants.

kristinalaudis3e

yes because isolated systems cant exchange energy or matter!

kristinalaudis3e

extensive depends on the amount of a substance (ex: mass) while intensive doesn't depend on the amount of a substance (ex: density).
it is important to know so that you can use the right constants in your equation

kristinalaudis3e

isolated systems can't exchange energy or matter so no outside sources can affect the reaction, open systems can exchange both energy and matter so a lot of outside factors can affect the reaction, and closed systems can only exchange energy so few outside sources such as temperature can affect the ...

kristinalaudis3e

since open systems allow for the exchange of matter and energy, I think that any thermodynamic equation can be used so long as you pay attention to if it has constant pressure and volume

kristinalaudis3e

Closed systems have a fixed amount of matter and don't allow for the exchange of matter. A clear example would be like the water bottle example mentioned above. A closed water bottle doesn't allow the water inside to leak!

kristinalaudis3e

I think for pressure, you need to know atm and torr!

kristinalaudis3e

Kc and Kp are calculated in the same way and both can be used for gases, but the only difference is that one is for partial pressures and one is for concentration. for whichever version you choose, make sure youre consistent with it the whole way through!

kristinalaudis3e

P is used to note that it is partial pressure being used instead of concentration! but both Kc and Kp can be used for gases

kristinalaudis3e

yes just multiply them!!

kristinalaudis3e

if it goes fro A+B--> C then it would be K but if it goes from C-->A+B then it would be 1/K

kristinalaudis3e

if it gives you the initial value, then the change is -(stoich coefficient)x but if there is no initial concentration, then the change is +(stoich coefficient)x

kristinalaudis3e

because K is a constant, the only thing that changes K is temperature :)

kristinalaudis3e

definitely use the ICE table as the other responses said, but also don't forget to divide the moles by liters in order to get molarity!

kristinalaudis3e

yes Q would change!!

kristinalaudis3e

when calculating, yes they are the same mathematically, but conceptually they are different. concentration is solely based on moles whereas partial pressures are related to temperatures and moles

kristinalaudis3e

I don't think Lavelle explained it either, but as long as you remember that they become exponents when calculating K and Q, then I think you should be fine :)

kristinalaudis3e

So in a triple bond, one is a sigma bond and 2 are pi bonds. For the sigma bonds, they will overlap end to end, but for the pi bonds, they have to overlap side by side. The 2 pi bonds are formed when the unoccupied p orbitals that are not overlapping end to end then overlap side by side with the oth...

kristinalaudis3e

How oxidation numbers, I know that you would usually look at the number of ligands attached to the central Atom and based off their charges calculate the oxidation number of the whole molecule, but if there is an atom attached to the outside (so not the central atom), can you use only that atom to c...

kristinalaudis3e

What exactly is the difference between these two? or can I assume that a Lewis acid is a bronsted base and a Lewis base is a bronsted acid.

kristinalaudis3e

For a lewis structure with 3 bonds and one lone pair have a bond angle closer to 106 (from lecture) or will it have a bond angle that is just less than that of a tetrahedral (109.5)?

kristinalaudis3e

Hello,

In lecture Lavelle stated that acid in a solution will be at pH 6. Does he mean the acid itself is at pH 6 or does he mean the solution will become pH 6?

kristinalaudis3e

London dispersion forces happen in all molecules because electrons are constantly moving around the nucleus and when electrons randomly become closer to each other, they create temporary dipoles which is a form of attraction.

kristinalaudis3e

Sigma bonds are in all bonds while pi bonds are only in double and triple bonds. In a single bond there is only one sigma bond. In a double bond, there is one sigma and one pi bond and in a triple bond there is one sigma and 2 pi bonds.

kristinalaudis3e

Hemoglobins transports oxygen through the blood and myoglobins store oxygen in the muscles

kristinalaudis3e

it can act as both!

kristinalaudis3e

high H+ count is acidic and low H+ count is basic

kristinalaudis3e

The hybridization of atoms depends on the number of regions of electron density. both C and O have 4 regions, therefore it has a sp3 hybridization.

kristinalaudis3e

I made 2 linear structures as well with the first containing double bonds between all 3 carbons and the carbons at the ends each have 2 hydrogens attached with a single bond. The next linear structure had the 3 carbons connected by a single and a triple bond. The single bonded carbon at the end has ...

kristinalaudis3e

having a delocalized pi bond means that the pi bond doesn't have one set place and had the option to be placed elsewhere within the molecule. You know that there are delocalized pi bonds usually when there are resonance structures.

kristinalaudis3e

sigma bonds occur in single, double, and triple bonds. I like to think of it kinda like how London forces are present in all bonds. The only additional info you need to know is that double and triple bonds also contain pi bonds, with double bonds having one pi bond and triple bonds having two.

kristinalaudis3e

it is a salt in a liquid state and has a really low melting point

kristinalaudis3e

A liquid crystal has properties between those of typical liquids and solids. They are able to flow like a liquid but will be arranged in a way similar to crystals.

kristinalaudis3e

How do I know if it will actually bond to make a coordinate covalent bond? I understand that one accepts the pair and one donates the pair, but how do you know if it will willingly donate?

kristinalaudis3e

How do I know how big expanded octets can expand?

kristinalaudis3e

CHI3 has a higher melting point because it has stronger bonds. Because of its size, it has more polarizability.

kristinalaudis3e

Can someone please explain what a dipole moment is? I know that dipoles have partial charges but what is a dipole moment?

kristinalaudis3e

How do I know the true length of bonds when there are resonance structures? Specifically, how do I know which ones contribute the most?

kristinalaudis3e

the higher the electronegativity of the atom, the stronger the pull on electrons meaning that the bond length would be shorter and stronger. same goes for atomic radius. if the atoms have a small radius, the electrons are more tightly held, meaning the bonds would be stronger and shorter. triple bon...

kristinalaudis3e

how do you know if you need to make the central atom have a double bond with the other atoms or if you can just leave them as lone pair electrons on the central atom?

kristinalaudis3e

the oxidation numbers of all the atoms should equal the charge on the whole compound. on the sapling question, we know that oxygen has an oxidation number of -2, so if there are four oxygens (-2x4=-8) and the whole compound needs to equal -1, then the oxidation number of chlorine should be +7

kristinalaudis3e

on the hint given by sapling, it states that the sum of the oxidation numbers is equal to the formal charge of the molecule. knowing that there was a formal charge of -1 on the whole molecule and that the four oxygens each had a oxidation number of -2 (totaling to -8), you can deduce the chlorine at...

kristinalaudis3e

why can't H make a hydrogen bond with carbon? I understand that hydrogen bonds can be made with N, O, and F because they're extremely electronegative and so they pull electrons towards them (making it partially negative), but then the difference in electronegativity of carbon and hydrogen is not sig...

kristinalaudis3e

Hi what is the general guideline for drawing lewis structures? Thanks!

kristinalaudis3e

1. odd number of electrons in molecules, ex: NO
2. when 1+ atoms in a molecule have 8+ electrons, ex: SF6
3. when 1+ atoms in a molecule have >8 electrons, ex: BCl3

kristinalaudis3e

I think they're relieved because the oxygen atom needs one electron in the p levels to be stable and when its ionized, the electrons are spinning in opposing ways.

kristinalaudis3e

Start by drawing the lewis structure of the compound and you'll notice that hydrogen bonds can occur for NOF atoms because they'll bond to the lone pairs. This means that there will be 8.

kristinalaudis3e

The answer is C because using the equation c=wavelength*v we know that c is a constant. Therefore if there are bigger wavelengths, then the frequency must decrease and if there are smaller wavelengths, then frequency must increase (they are inversely related). The change in the electrical field refe...

kristinalaudis3e

An easy way to remember atomic radius size trends on the periodic table is that it increases going to the left and it increases going down. The explanation above does a good job of explaining why, but this is just a little too for memorization purposes :)

kristinalaudis3e

The trend for electron affinity on the periodic table is that it increases from left to right and it decreases from top to bottom. Those with high electron affinity are also more likely to release energy when placing an electron while those with low electron affinity will absorb energy. Therefore, B...

kristinalaudis3e

When an electron has a high electron affinity, it will release a lot of energy when it gains an electron while one w a low electron affinity will release very little energy and absorb it.

kristinalaudis3e

Hello, Ionization energy is the energy needed to remove an electron, so I guess it could just describe the concept as a whole, whereas the first ionization energy is the energy needed to remove an electron from a neutral atom while the second ionization is the energy needed to remove an electron fro...

kristinalaudis3e

An excited electron is one that gains energy through photons and this makes it move to an energy level higher than the ground state. I like to think of the ground state as the base level that electrons are already on. So when it moves from a higher energy level back to its ground state, it is releas...

kristinalaudis3e

They were able to discover that atoms had a concentrated mass within the nucleus (including all the positive charges) through their foil experiment because of how the the alpha particle beamed scattered after hitting foil. They found that most of the particles could go through and only a tiny fracti...

kristinalaudis3e

Covalent bonds are the strongest bonds, hydrogen bonds are the weakest, and ionic bonds are moderately strong. I hope this helps :)

kristinalaudis3e

I agree with the statement above. In the photoelectric effect, we want the energy in the photon to be enough to eject one electron. Therefore, they would have to be a 1:1 ratio. Hopefully, this is helpful!

kristinalaudis3e

To convert 300 MHz to Hz you would multiply it by 10^6. This is because Hz refers to the frequency, in which one cycle goes every second. MHz or Megahertz indicates millions, which is 1 x 10^6. I hope this helps!

kristinalaudis3e

For the most part, the limiting reactant determines how much products can be produced with the full consumption of that reactant, so technically yes. Making less products than calculated possible with the limiting reactant is also a possibility. I hope this helps!

kristinalaudis3e

Yes they are the same! It is essentially like math where if you have something in parentheses and they are multiplied by a number, that number gets distributed to everything inside the parentheses. In this case, (OH) has a subscript of 2, there for it would be distributed to the O and the H to make ...

kristinalaudis3e

When you multiply or divide, your answer should have the same number of sig figs as the value with the smallest number of significant figures. 55.5 (3 sig figs) / 2.5 (2 sig figs) = 22.2, but you need only 2 sig figs so it would be 22. When you add or subtract, you answer should have the same number...

kristinalaudis3e

For the second stage, I believe those are the right compounds, but you just have to balance them. So from what we know about Fe3O4 + CO -------> Fe + CO2, we can see that there is more Fe on the left than the right. To balance this, we simply add a 3 in front of the Fe on the right to create Fe3O4 +...

kristinalaudis3e

They multiply and divide normally. For mw personally, it may be a little more work but I take the terms out of their scientific notation and multiply/divide normally, then put my answer back into scientific notation with the correct number of sig figs. This helps me make sure that I am doing it corr...

kristinalaudis3e

I was also confused about this when doing the sapling homework, as I tried to use m1v1-m2v2 when in reality all I had to do was use m=n/v. I think from that problem I learned that you just have to look closely at what they give you. if the question gives you any 3 parts of the m1v1=m2v2 formula, tha...

kristinalaudis3e

Should we always be using scientific notation for our answers? I know this question can be a little vague so if anyone has any overall tips for when to use scientific notation/how to use scientific notation I would really appreciate it!

kristinalaudis3e

I think for more accuracy, you should keep all the decimals during intermediate steps and then use sig figs for your final result. For example, if you get an answer during step one and then round it and then use that rounded number for step two and so on, the likelihood of error increases between ea...

kristinalaudis3e

To begin, there are 4 rules for sig figs. 1. any digit that isn't a 0 is significant 2. any zeros sandwiched between 2 non-zero digits are significant 3. leading zeros aren't significant 4. if there is a decimal point, any zeros trailing a non-zero digit is significant Therefore, 0.005 actually has ...

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