CHEMISTRY COMMUNITY

Areena H 2K

I'm having a hard time understanding why the entropy of the surroundings increases more if temperature is lower than if it is higher? Is it because a lower temperature means its more endothermic or is there another reason?

Areena H 2K

I think that it would be best to know them in case they come up on the exam. Isobaric is pressure, isothermal is where temperature is held constant, and isochoric is where volume is held constant.

Areena H 2K

Irreversible would be pumping air into a balloon or gas bump and it happens suddenly while reversible would be slowly adding air into it gradually.

Areena H 2K

Lead has more molecules and since it is a larger number, it has more electrons, protons, and neutrons leading it to a larger mass as well

Areena H 2K

For 4G.1 a) how can we tell how many microstates there are if they are aligned in the same way? Do we look at the orientation or number of molecules?

Areena H 2K

Why is the internal energy equal to 0 in an isothermal process (Q=W)?

Areena H 2K

Why is the internal energy equal to 0 in an isothermal process (Q=W)?

Areena H 2K

When q equals delta H that means that pressure is constant in the system. There is also no other work being done on the system.

Areena H 2K

I think looking at the constant equations sheet and knowing how to manipulate the formulas based on what we're given should be able to be enough. You can also write them out on your own on a separate piece of paper.

Areena H 2K

I think drawing out the lewis structures is the best way to practice bond enthalpies because you can have it drawn out based on the structure with the lowest formal charge, which will help you know where the bonds break

Areena H 2K

From lecture, we talked about a bomb calorimeter which is an isolated system and insulation, and also an open calorimeter, and adiabatic calorimeters as well.

Areena H 2K

I think mass is used for specific heat capacities and molar capacities. I'm not too sure when we don't use it.

Areena H 2K

Bond enthalpies are the amount of energy required to break bonds while standard enthalpies are the change sof enthalpy during the formation of 1 mole of the substance from its elements

Areena H 2K

You would start by putting the one with the lowest ionization energy in the middle, count the number of valence electrons and then place them, and then move the around until you get the structure with the lowest formal charge (count electrons and lines and subtract)

Areena H 2K

What is the best method to use considering we try to not use bond enthalpies since they aren't very accurate?

Areena H 2K

Are bond enthalpies not an accurate method because the bond enthalpy for each atom is considered an average or is there another reason?

Areena H 2K

What's the reasoning behind why work and heat are not state functions?

Areena H 2K

I feel its good to know the strong ones just in case. Know how to calcuate the ph, poh, find the molar concentrations, be able to use kw to find the ka or b, and be able to do the ice tables.

Areena H 2K

A buffer is used to maintain the ph of a solution and keep it relatively constant. Weak acids and their conjugates are used for buffers

Areena H 2K

Inert gases are all of the noble gases in the last column of the periodic table. They are not reactive so they don't react during chemical equations so for la chateliers principle, inert gases don't have any effect on the reaction

Areena H 2K

I believe the ph can be above or below 14 but generally, the range it falls under is 0-14

Areena H 2K

If K is greater than Q that means that at point during the reaction, there are more reactants that are forming and to reach equilibrium the reaction proceeds to the right which is saying that more products are formed.

Areena H 2K

When K is really small we can say that the difference would be negligible or very small so we can use that to exclude X.

Areena H 2K

Is Kc only for aqueous solutions while Kp is for gases because there was a question in the lecture where it had gases but was still using Kc?

Areena H 2K

Does this mean that if you have left-shift you produce more reactant and right-shift means you produce more product?

Areena H 2K

I'm just a little confused on when we know when to use ICE Tables or not when calculating partial pressure? Are there certain circumstances when we use it?

Areena H 2K

Why does removing or adding an inert gas in a chemical equation not change the equilibrium constant? Adding or removing an inert gas affects the pressure and physical parameters based on La Chatalier's Principle since physical parameters cause a shift in the reaction, so why do we say that inert gas...

Areena H 2K

If you have a metal hydroxide that reacts with water, will your net equation be oh- and h20 or 2h2o?
For example
MOH + H20 --> M+ + OH- + H2O
vs
MOH + H3O+ --> M+ H20?
Is this essentially saying the same thing because we are taking H3O+ out of solution to make H2O or is it different?

Areena H 2K

When you have electron withdrawing groups and the oxyacids with more oxygen atom weaken the o-h bond and the H+ proton is removed, would the oxygen that was bonded to an H still have a - charge or will it form a double bond top stabilize the molecule with no formal charge?

Areena H 2K

Is the solution neutral when your Pka equals your ph? Is it acidic when your pka is greater than your ph? And would we say that when your pka is lower than your PH then your solution is basic or is it the opposite?

Areena H 2K

The book mentions the formation constant Kf for finding equilibrium for coordination compounds. Do we need to know how to set this up the same way as the acids and bases Ka constant with products over reactant?

Areena H 2K

For each ligand to act as a lewis base, the more lone pairs it has to donate, the more sites it can bind to? So if an atom has 4 lone pairs, it would then be polydentate?

Areena H 2K

It will depend if the acid or base is weak or strong. If it dissociated completely, we will know it is strong and it does not it is weak

Areena H 2K

I think theres a table/chart in the book that we can use! You can also google some common ones for more help.

Areena H 2K

I believe that NH3 is a base, specifically a weak base.

Areena H 2K

Due to strong acids being able to dissociate, the conjugate base will have no acidic properties at all, so it will be just basic.

Areena H 2K

Bronsted acids are talking about proton donors/acceptors and lewis acids and bases refer to electron proton donors/acceptors.

Areena H 2K

I would assume that we should know how to draw the examples and how they bind to different ligands.

Areena H 2K

I think it would be helpful to know cisplatin as it was discussed in lecture as well as the hemoglobin example.

Areena H 2K

I think its due to the fact that cisplatin can bind 2 regions of the DNA and block cell replication. Even though it has side effects such as killing normal cells, it does effectively kill the cancer cells.

Areena H 2K

Do the ligands only attach to transition metals? Why not an element that is not a transition metal?

Areena H 2K

Cis would be when the 2 atoms bond are on the same side and trans is when they are on opposite sides

Areena H 2K

The molecule overall would be considered nonpolar so it would have no dipole-moments.

Areena H 2K

Do we need to know T shaped geometry even if Dr. Lavelle didn’t go over it in lecture?

Areena H 2K

Does geometry of molecules play a role in hydrogen bonding for example H2O2 being written out straight or in a bent formation?

Areena H 2K

Let's say I want to name the intermolecular force between SO4 that is a nonpolar molecule but has bonds that their electronegativity difference is greater than 0.4 and we have water that has a net dipole, would we classify this as dipole-induced dipole or dipole-dipole

Areena H 2K

Yes, typically this is the accepted value for nonpolar interactions. However, a molecule can still be nonpolar if the difference in electronegativity is greater than 0.4 but the polarity is symmetrical. This can be seen in molecules such as carbon dioxide. Let's say I want to name the intermolecula...

Areena H 2K

When we refer to nonpolar bonds are we saying that the the electronegativity difference has to be less than 0.4 to classify it as nonpolar?

Areena H 2K

The size and charge of an ion determines its polarizability. The larger anion has a larger electron cloud that can be distorted and also has a lot of electrons shielding it from its nucleus therefore if another cation is close by its strong nuclear pull is going to attract the anions large electron ...

Areena H 2K

Everything third row and beyond can have expanded octets because they have d shells that are available for them to use, therefore they can all have expanded octets.

Areena H 2K

It can be drawn in several different ways, but the best way to determine where the radical goes is to find the structure with the lowest charges on it.

Areena H 2K

Delocalization means that electrons don't just surround one area such as near an atom or a single or double bond, they like around the molecule and spread out over the entire space

Areena H 2K

Delocalization means that electrons don't just surround one area such as near an atom or a single or double bond, they like around the molecule and spread out over the entire space

Areena H 2K

The most electronegative atom has the most negative charge on it, but when we want the lowest energy structure with the least amount of formal charges as possible.

Areena H 2K

Does second ionization energy mean that after the electron is first removed, what is the likelihood that the second will be removed as well for elements in the s block that have lower ionization energies than p block?

Areena H 2K

Yes this trend continues because it provides symmetry and the electrons would rather want to go into an orbital by itself rather than be next to another paired because they of e-e repulsion. Therefore, there is more stability and symmetry in half filled and full filled shells.

Areena H 2K

Liliana Aguas 3G wrote:It's when they have the same number of electrons and same electron configuration! Section 1F.3 explains it with some examples:)

So two elements would have to have the same number of electrons as well which would then be the same electron configurations for both?

Areena H 2K

I think it just helps you find which shells you are removing the electrons from. You don't have to write out the ground state configuration if a question doesn't ask but it just helps you make less mistakes especially when we get into the 4th row and remember that we remove electrons from the 4s ene...

Areena H 2K

I think that for the purposes of this class we only cover the quantum numbers from l=0,1,2,3, 0 being s, 1 being p, 2 being d, and 3 being f. We don't really talk about the g and h, etc. subshells so we only go to l=3.

Areena H 2K

For hydrogen all of the subshells are considered degenerate but for multi-electron atoms is each orbital within each subshell degenerate ex: 2p all of the three orbitals are degenerate and for 3d all of the five orbitals are degenerate?

Areena H 2K

The midterm will cover fundametals, the quantum world, and chemical bonds, I believe!

Areena H 2K

No I don't think so. I think he only uploads the high school fundamentals and quantum because they're the beginning topics we learn, the fundamentals as a refresher and the quantum since it is a bit more difficult to understand.

Areena H 2K

Do we need to know just the general concept of effective nuclear charge or we need to know how to calculate it as well Z(eff)-S (number of protons- number of shielding electrons

Areena H 2K

If we have a light that has sufficient energy to allow electrons to escape the surface of a metal, will changing the intensity (amplitude) of that particular light cause any effect on either the number of electrons being ejected or the kinetic energy that those electrons will have?

Areena H 2K

I believe Threshold Frequency is the amount of energy of a photon required to displace an electron on a metal surface. The photon needs to at least match the threshold, which will result in a kinetic energy of 0. Yes that part makes sense to me but when we're calculating the threshold frequency, is...

Areena H 2K

Can someone clarify on the threshold frequency? Is it the work function times planck's constant?

Areena H 2K

Typically I was told in discussion that wavelengths are given in nm but meters are used as well and picometers.

Areena H 2K

I believe the masses are provided on the contstants and equations sheet as I know were given the mass of an electron but maybe it would be could to memorize proton and neutron just in case it’s not on the sheet.

Areena H 2K

The Balmer series is where the electron falls from its state and goes to n=2 and its in the visible light spectrum. The Lyman series where the electron drops to n=1 and it is in the uv region

Areena H 2K

Will the answers be posted for those of us who can’t attend the sessions to make sure we get the correct answer?

Areena H 2K

I think because we’re still covering the quantum world I think we can still do 5 problems from that section

Areena H 2K

Dr. Lavelle hasn't mentioned if he prefers them in scientific notation or not, however I assume he wants us to know how to use it but questions don't specifically ask to format it into scientific notation so I don't we have to, it is just preferred. As for, sig figs my ta said on the exams they won'...

Areena H 2K

The T stands for tons so 1 ton is equal to 1,000 kg and then we use dimensional analysis to convert from kg to g by using 1 kg equals 1,000 grams.

Areena H 2K

There is no course reader for the class this year, just the textbook.

Areena H 2K

The simplest way would be to convert from the units given to the base which would be meters and from meters to angstroms or if another unit is given such as pm concert to m then angstroms.

Areena H 2K

I am pretty sure Dr. Lavelle said to get the posts in by Sunday, assuming its by the end of the night so 11:59 pm

Areena H 2K

The sig fig rules depend on if a certain amount of them are given in the problem, if they are then your final answer should contain the same amount of sig figs, if they are not then depending on multiplying/division you use the sig figs of the smallest number for your answer and for addition and sub...

Areena H 2K

I think it is best to keep the units given unless they specially ask for a conversion or ask for different units. If they don't ask you to do that then it is prob best to keep the same units they gave you.

Areena H 2K

Usually, I will keep the full number in my calculator to be as accurate as possible but for my work I will usually go to 5 sig figs or 4 and then I will round my answer towards the end.

Areena H 2K

The Zeros before the 1 do not count. Therefore to get 5 sig figs, you must add a 0 after the five to make it significant so no rounding is necessary here.

Areena H 2K

Loved reading about your experience! Thank you for sharing this with us but I was wondering what kept you motivated to keep going? I know a lot of people just give up because it is too difficult from or switch career paths because they think they're not able to continue with medicine.

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